汤国安. 我国数字高程模型与数字地形分析研究进展. 69(9): 1305-1325 TANG Guoan. Progress of DEM and digital terrain analysis in China. Acte Geographica Sinica, 69(9): 1305-1325
基金:国家自然科学基金项目 (41171320); 江苏省高等学校重大科研计划项目 (13KJA170001); National Natural Science Foundation of China, No.41171320; Major Scientific Research Projects of Universities in Jiangsu Province, No.13KJA170001
Progress of DEM and digital terrain analysis in China
TANG Guoan
School of Geography Science, Nanjing Normal University, Nanjing 210046, China
Abstract
Digital elevation model (DEM) is known to be one of the most important national fundamental geographic information data. The theory, method and application of digital terrain analysis (DTA) based on GIS is a hot research issue in geography, especially in the field of geographical information science. This paper makes an overall review on Chinese scholars’ contribution to the research of DEM and DTA, especially to DEM data model, uncertainty, analysis method, scaling effect and high performance computing method, as well as its application in DTA. A few research groups in this field have made great progress recently, and young scholars are playing a critical role in the process. Their research has caught up with the international forefront, and achieved fruitful results in significant innovation. Some research, like DEM based regional geomorphological research on the Loess Plateau and Tibetan Plateau of China highlighted the contribution of Chinese scientists, which have had influence in the international academia to a certain degree.
Keyword:
digital elevation model; digital terrain analysis; geomorphology; geomatics; geographic information science; review
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A method of gridbased DEM construction in terms of Coons patch has been presented. Two examples including a numerical test and a real-world example were employed to comparatively analyze the simulation errors of Coons patch and the classical interpolation methods including IDW, SPLINE and KRIGING. Gaussian synthetic surfaces with various terrain complexity controlled by coefficient parameters were simulated and the results indicated that with the increase of terrain complexity, the simulation errors of all the methods willincrease as well. The Coons patch is much more accurate than the classical methods. The real-world example was used to test the effect of sampling interval on the simulation accuracies of all the interpolators. The results indicate that sampling interval has a negative effect on the simulation accuracy. However, the Coons patch is more accurate than the classical interpolation methods regardless of sampling interval. In terms of simulation accuracy and computing speed, Coons patch can be considered as an alternative method for DEM construction.
Geometics College Shandong University of Science and Technology,Qingdao 266590
For the problem that traditional algorithm of point by point interpolation based on Delaunay triangulation network can not give attention to both interpolating precision and executing efficiency, and according to the geometry characteristics of both Voronoi cells and Delaunay triangles, the paper brings forward the algorithm of point by point interpolation based on local dynamic optimal Delaunay triangulation network. Some experiments that interpolating multibeam survey data into grid digital depth model(Grid DDM), have been done to validate the algorithm’s validity. The experiment results show that the algorithm is characterized by good interpolating precision, meanwhile, the executing efficiency is also improved.
1 Department of Hydrography and Cartography,Dalian Naval Academy, 667 Jiefang Road, Dalian 116018,China
针对传统的基于Delaunay三角网的逐点内插算法难以同时兼顾精度和效率的问题,依据Voronoi单胞和Delaunay三角形的几何特性,提出了一种基于局部动态最优Delaunay三角网的逐点内插算法,并在格网数字水深模型(grid digital depth model,Grid DDM)中进行应用。实验结果表明,该改进算法能保证插值精度并明显提高执行效率。
顾及地形特征线的散点域(约束数据域)三角剖分是建立高精度数字地面模型的基础,在GIS、地学分析、计算几何、多分辨率DTM等领域中有着广泛的应用。本文研究了约束数据域的Delaunay三角剖分问题,简要分析了现存的算法特点并提出了约束数据域的Delaunay三角剖分的迭代算法和删除算法。 Abstract: The triangulation of constrained data set is widely used inGeographic Information System(GIS),geo-science,computational geometry,multi-resolution and high precision DTM, et al. This paper researches the triangulation of constrained data set and briefly analyses some existing algorithms. A new iterative algorithm and deleting algorithm for triangulating constrained data is proposed.
YueTianxiang, DuZhengping, SongDunjiang, et al. A new method of surface modeling and its application to DEM construction. Geomorphology, 2007, 91(1/2): 161-172.
ChenChuanfa, YueTianxiang. A method of DEM construction and related error analysis. Computers & Geosciences, 2010, 36(6): 717-725.
Abstract The concept and the computation of terrain representation error (ETR) are investigated and total DEM error is presented as an accuracy index for DEM evaluation at a global level. A promising method of surface modelling based on the theorem of surfaces (SMTS) has been developed. A numerical test and a real-world example are employed to comparatively analyze the simulation accuracy of SMTS and the classical interpolation methods, including IDW, SPLINE and KRIGING performed in ARCGIS 9.1 in terms of sampling and interpolation errors and of total DEM error. The numerical test shows that SMTS is much more accurate than the classical interpolation methods and ETR has a worse influence on the accuracy of SMTS than those of the classical interpolation methods. In a real-world example, DEMs are constructed with SMTS as well as the three classical interpolation methods. The results indicate that, although SMTS is more accurate than the classical interpolation methods, a real-world test indicates that there is a large accuracy loss. Total DEM error composed of, not only sampling and interpolation errors, but also ETRs can be considered as a good accuracy measure for DEM evaluation at a global level. SMTS is an alternative method for DEM construction.
A new DEM which is called features preserved Grid Digital Elevation(F-DEM) is proposed in this paper.The F-DEM is based on the "Vectorizing simulation and rasterizing organization" method and combines characteristics both of the terrain the physical objects by applying the object-oriented technology.Through abstractly describing terrain characteristics based on their morphology and seamlessly embedding terrain features information into general grid data with segmentation technology,F-DEMs not only can maintain the structural integrity of grid DEM,overcome the disadvantage of imprecision terrain description in some places containing break terrain features,but also can keep its efficiency of terrain simulation with preserved features,which is of critical significance to research high-fidelity DEMs.
1 Land Information Engineering Department,Chuzhou University,80 South Fengle Road,Chuzhou 239012,China; 2 China Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University,1 Wenyuan Road,Nanjing 210046,China
Hydrologically correct DEMs(Hc-DEM) is one of DEMs which correctly and sufficiently represents genesis and locational relationship between hydrologic parameters,including direction and pathway of overland runoff,stream networks,and boundary of watershed,and landform,etc.As the only way to extract terrain parameters based on DEMs for the studies of watershed hydrology,and soil erosion modeling of regional scale,therefore it is necessary to constructing Hc-DEMs for representing terrain shape,extracting terrain and hydrology parameters.In this paper,the concept,constructing method of Hc-DEMs were introduced and discussed,then taking Loess Plateau as an example,key parameters for Hc-DEMs constructing based on digital topographic maps and ANUDEM software package were identified by series tests;the quality of resultant DEMs have been assessed by comparing them to DEMs from TIN approach which is widely applied in China.The results show that varied resolution Hc-DEMs can be generated based on available digital topographic maps,including features of contour,spot heights,stream lines,etc,and ANUDEM software,and provide solid support for hydrology and soil erosion modeling at the watershed/regional scales,and mapping of vegetation suitability.
1.Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,712100,Yangling,Shaanxi,China;2.CSIRO Land and Water,GPO Box 1666,Canberra,2601,ACT,Australia
Yang QK, McVicarT R, Van NielT G , et al. Improving a digital elevation model by reducing source data errors and optimising interpolation algorithm parameters: an example in the Loess Plateau, China. International Journal of Applied Earth Observation and Geoinformation, 2007, 9(3): 235-246.
Abstract A hydrologically correct digital elevation model (DEM) forms a basis for realistic environmental modelling, especially in complex terrain. We have performed a study in the Coarse Sandy Hilly Catchments (CSHC) of the Loess Plateau, China, which demonstrates pragmatic, yet effective methods for improving the quality of the DEM by: (1) identifying and correcting source topographic data errors and (2) optimising ANUDEM algorithm parameters. Improvement in the DEM based on fixing over 1100 errors in the input topographic data, and optimising key ANUDEM parameters was assessed using higher accuracy independent validation of 32 contributing areas and 1474 spot heights, and by semi-quantitative analysis of DEM derivatives produced from ANUDEM and Triangular Irregular Network (TIN) algorithms. Improvement in the ANUDEM DEM over the original TIN DEM was shown where the percentage of the total absolute difference in contributing areas reduced from 10.43 to 3.51%, and the bias between the spot heights and DEM elevations reduced from 45 to 32 m. Large improvement in DEM quality was gained by using ANUDEM instead of TIN, with smaller improvement gained by fixing source data errors, and optimising ANUDEM parameters.
Using spatial autocorrelation analysis,the digital elevation error is studied;and the results show that there is no significant global spatial autocorrelation of digital elevation error in all cells,the spatial pattern of digital elevation error is random on the whole.There is significant local spatial autocorrelation between one cell and its neighbors,and the difference of digital elevation error between one cell and another is small,the spatial pattern of digital elevation error converges strongly in local areas.
1 School of Sciences,Information Engineering University,73 Songshan South Road,Zhengzhou 450001,China; 2 Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University,1 Wenyuan Road,Nanjing 210046,China
We provide an overall review of the present standing of research in digital elevation model(DEM) error,focusing mainly on the four aspects: DEM propagation error,DEM error models based on the measure of mean square error(MSE) and the problems that have arisen in the using of MSE measure,DEM error distribution experiments,and new understanding of DEM interpolation error.It addresses the following viewpoints: the foundation of the use of MSE measure to assess DEM propagation error is error propagation theory,however,using MSE measure to assess DEM interpolation error and the total error lacks a theoretical basis.On the other hand,the spatial patterns of error distribution shown in many DEM error experiments have cast considerable doubt on the usefulness of MSE-based measures,but the spatial property of DEM error can be explained by the DEM error model based on approximation theory.It is correct and feasible to apply approximation theory to discuss DEM interpolation error.
1 School of Resource and Environmental Science,Wuhan University,129 Luoyu Road,Wuhan 430079,China
The spherical harmonics transform is a method to improve the calculation speed of the earth’s gravity disturbsance on orbiting satellites.Based on the particularity of the trajectory for pole transformation,the Clenshaw sun method is introduced to calculate the gravity disturbance on the new coordinates.Then,a comparative analysis focuses on the calculation speed and physical space needs using three methods;the traditional,pole transform,and improved pole transform methods.A simulation using the three methods is used to calculate the gravity disturbance on one period of the orbit.Test results show that the improved pole transformation of spherical harmonic functions is 100 times the calculation speed of the traditional pole transformation method.Furthermore,the data storage capacity required by the new method is only three percent of the traditional method.
1 Faculty of Geomatics,East China Institute of Technology,418 Guanglan Road,Nanchang 330013,China; 2 School of Geodesy and Geomatics,Wuhan University,129 Luoyu Road,Wuhan 430079,China; 3 Institute of Earthquake Science China Earthquake Administration,63 Fuxing Road,Beijing 100036,China
ZhangYong, TangGuoan, PengQi. A mathematical simulation of DEM terrain representation error: A case study in the loess hill-gully areas of China. Journal of Mountain Research, 2003, 21(2): 252-256. [张勇, 汤国安, 彭釮. 数字高程模型地形描述误差的量化模拟: 以黄土丘陵沟壑区的实验为例. 山地学报, 2003, 21(2): 252-256. ]
Based on estimating rule of the normal vector angles between two adjacent terrain units,we use the conception of Terrain Complexity Factor to quantify the terrain complexity of DEM,and then the formula of Terrain Complexity Factor in Raster DEM and TIN DEM has been deduced theoretically.In order to make clear how the Terrain Complexity Factor h-and the Average Elevation RMSEEt affect the accuracy of DEM Terrain Representation RMSEEt,the formula of Gauss Synthetical Surface has been hired to simulate several real terrain surfaces,each of which has different terrain complexity.Through the statistical analysis method of linear regression in simulation data,the linear equation between Accuracy of DEM Terrain Representation RMSEEt,Terrain Complexity Factor ECF and the Average Elevation h-has been achieved.We provide a new method to estimate the accuracy of DEM Terrain Representation RMSEEt with a certain terrain complexity,and also will supply convincing theoretical evidence for DEM production and the corresponding error research in the future.
1 Department of Surveying and Geo-Informatics,Tongji University,1239 Siping Road,Shanghai 200092,China; 2 Key Laboratory of Advanced Engineering Survey of SBSM,1239 Siping Road,Siping 200092,Shanghai
Drainage information plays an important role in the presentation of spatial information and is widely used in terrain analysis, resource and environment management and Hydrology. Watershed, which indicates the characteristic of geology, geomorphology and hydrology, is a basic object in the research of earth surface hydrology. And it is very important in soil and water conservation and environmental monitoring. The automatic extraction of valley lines based on grid DEM is the base of the researches mentioned above. And the flow direction determination is one of the most important parts in the automatic ditch extraction. In this paper, we summarized and implemented the existing algorithms of flow direction determination in automatic ditch extraction, and proposed a new algorithm of flow direction determination, in which multiple flow directions and randomness were accounted for, based on the FD8 and Rho8 algorithm. We used two DEM data to validate the advantage of this algorithm in multiple flow direction and randomness.
Through 50 years of development, theory and methodology of DEM itself and DEM based digital terrain analysis (DTA) have been matured gradually, and played key roles in hydrology, geomorphometry, soil sciences, environmental science, agriculture, geologic hazard, civil engineering and military affairs. Based on an overall retrieval analysis of previous researches, this paper classifies different methods of DTA into four classes, i.e. analysis of terrain factor, terrain feature extraction, terrain statistical analysis and DEM based geo-modeling. Secondly, uncertainty and the scale issue of DTA are discussed. Besides, this paper points out that scale effect, optimal scale and scale transform are three basic scale issues of DTA. Thirdly, applications of DTA in geomorphometry, hydrology, soil science, agriculture, geologic hazard are introduced. Finally, this paper proposes that the conceptual framework of DTA, the accuracy of DEM modeling and the method of terrain analysis need to be improved, especially the integrated method of DEM embedded geographical modeling, for the simulation of more lifelike natural environment.
Key laboratory of Virtual Geograpgic Environment of Ministry of Education,Nanjing Normal University, Nanjing 210046,China
Precision of DEM terrain information content is a key factor to judge the applicability and limit of DEM data. An experiment is designed to find out the effect of DEM subset partition strategy and number of subsets to the estimate precision of DEM terrain information content based on DEM, slope and aspect data of hilly and gully test areas on the Loess Plateau. The result shows that DEM terrain information content is affected by both terrain information and subset partition strategy. To weaken the uncertainty of DEM terrain information content calculated by traditional algorithms, this paper presents a DEM subset partition model based on the maximum entropy theorem. It provides an objective theoretical basis for DEM information content calculation and has been proved efficient to avoid the subjectivity and arbitrariness in DEM artificial classification.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing, Jiangsu 210046; 2. Land Information Engineering Department, Chuzhou University, Chuzhou, Anhui 239000
DongYoufu, TangGuoan. Research on quantification model for elevation point's terrain information based on DEMs. Geographical Research, 2012, 31(10): 1825-1836. [董有福, 汤国安. DEM 点位地形信息量化模型研究. 地理研究, 2012, 31(10): 1825-1836. ]
For a given point embedded in grid DEMs, its comprehensive quantification model of terrain information content representing its significance in approximating the true terrain surface is constructed on the basis of information theory after its terrain syntactic information content is measured with differential geometry algorithm, and its terrain semantic information content is determined according to the terrain feature type and the global terrain structure.Then, choosing a study area of 70km 2 in the loess gully region with a resolution of 5m, the paper discusses the extraction procedure of the terrain information content for a grid point based on grid DEMs and an application in multi-scale terrain generalization based on grid point's terrain information content.Experimental results show that the terrain information measurement model for a grid point is feasible and the multi-scale DEMs reconstruction method is not only easy to implement but also effective in reducing terrain distortion by preferentially keeping a set of“surface-specific”structural points located in global terrain skeletons.The application example proved that the multi-scale DEMs constructed by selecting critical points based on their terrain information content values could meet the demands of digital terrain modeling in different terrain scales. Therefore, the research could be helpful in deepening our understanding of DEM terrain information characteristics and offering a theoretical and methodological support for multiscale digital terrain modeling.
1. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing 210046, China; 2. College of Geomatics Engineering, Nanjing University of Technology, Nanjing 210009, China
TaoYang, TangGuoan, WangChun, et al. Assessment on surface roughness models based on semantics and profile characteristics matching. Geographical Research, 2011, 30(6): 1066-1076. [陶旸, 汤国安, 王春等. 基于语义和剖面特征匹配的地形粗糙度模型评价. 地理研究, 2011, 30(6): 1066-1076. ]
As an important terrain factor, surface roughness calculated by digital elevation models (DEM) is directly used in geoscience models such as soil erosion models, surface photo-thermal simulation and so on. But there has been no generally accepted definition of surface roughness until now. Various types and similar concepts of surface roughness may cause difficulty for selecting a suitable surface roughness model. In this paper, we present a new algorithm for assessing surface roughness models based on semantics and profile characteristics. Some contrast experiments are presented by choosing hybrid landform types as sample areas, using DEM produced by traditional topographic map digitizing and LiDAR technology. Main conclusions are drawn as follows: (1) The method we presented in this paper can accurately express the local variation of terrain profiles suitable for assessing surface roughness models. (2) Both triangular boundary effect of TIN model generated by traditional contour based DEM production and surface random noise in DEM generated by LiDAR technology based DEM production influence the calculation of surface roughness. DEM data should firstly be filtered and noise reduced beforehand. (3) An SAR model is insensitive to the flat relief. It is not suitable for areas of plain and valley plain dominated areas. Roughness models based on vector calculus are accurate in expressing ridge and valley lines and straight slope areas which is not effectively described by SAR models. SDev model is more suitable for application in fine scale DEM. Slope based standard deviation model can be applied to most types of terrain, which is sensitive to four semantic rules. But SDsp model is more sensitive to break of slope.Curvature based standard deviation models are not advantageous in surface roughness description except for their high sensitivity in surface roughness of flat relief areas.
1. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing 210046, China; 2. Land Information Engineering Department, Chuzhou University, Chuzhou 239000, Anhui, China
ZhaoMingwei, TangGuoan, ZhangLei, et al. The DEM based 5-node second-order finite difference model for slope computation. Journal ofGeo-Information Science, 2012, 14(3): 286-291. [赵明伟, 汤国安, 张磊等. 基于DEM的5节点二阶差分坡度算法模型与实验分析. 地球信息科学学报, 2012, 14(3): 286-291. ]
Slope is the most basic terrain parameter to construct geo-science models. The accuracy analysis of the computing model is one of the most important issues in the geo-science. A lot of studies focused on error analysis of the computing model over the past few decades. The source of the error and the relationship between the error and the other parameters were studied. However, few studies were aimed to put forward a new model to decrease the error, which is more important for high resolution DEMs. By analyzing the error source of the slope computing model, this paper put forward a new model called 5 Node Second-order Finite Difference (5N-2FD). The characteristic of this model is that it is able to consider the multi-distance neighbor node: firstly it builds two difference models using different grid sizes, and then combines the two models into one with different weights. It is proved that it can improve the accuracy of the results remarkably through mathematical analysis. In this paper, a mathematical surface is selected to verify the accuracy of the new model. In order to study the influence of the resolution to the accuracy of the slope, this paper generated DEMs from the mathematical surface with different resolution, one is 1m, and the other is 5m. The results show that the new model can significantly improve the accuracy of the result compared with the common models. This study enriched the method system of digital terrain analysis, and provided slope data of high accuracy for many geo-science models. In addition, besides slope, there are many terrain parameters which are calculated through finite difference, such as aspect and various kinds of curvature, and the methods of this paper could afford some useful references in improving the accuracy of such terrain parameters.
1. Key Laboratory of Virtual Geographical Environment, Ministry of Education, Nanjing Normal University, Nanjing 210046, China; 2. School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
LangLingling, ChengWeiming, ZhuQijiang, et al. A comparative analysis of the multi-criteria DEM extracted relief. Geo-Information Science, 2007, 9(6): 1-6, 135-136. [郎玲玲, 程维明, 朱启疆等. 多尺度DEM提取地势起伏度的对比分析. 地球信息科学, 2007, 9(6): 1-6, 135-136. ]
The slope and relief are commonly used parameters in describing terrain.In the regional study,using the DEM data to draw relief can reflect the terrain characteristics fast and directly.The slope is mainly used to divide plain and mountain region,and the relief is mainly used to sub-divide the hills,small rolling mountain,middle rolling mountain and the great rolling mountain.The basic landform type is determined by criteria of relief and elevation,and it is also the foundation of division for more detailed landform classification by remote sensing.In this article,with DEM data including 1∶250 000 and 1∶100 000 of the study area,the slope is calculated to draw up plain and mountain region with a critical slope value of being approximately 3°;using the method of increasing grid window progressively in ArcGIS space analysis,which corresponds to different DEMS,the relief is calculated to determine the best window area which is set to be 4.41km 2 ;and using statistical method based upon comparison several different measures of the existing research results,the functional map of the study area between relief and the best window area is worked out.This research has certain model function when extracting the basic landform type in low mountain and hilly regions.
1. Research Center for Remote Sensing and GIS, School of Geography, Beijing Normal University, Beijing 100875, China; 2. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
ZhangWei, TangGuoan, TaoYang, et al. An improved method to saddles extraction based on runoff concentration simulation in DEM. Science of Surveying and Mapping, 2011, 36(1): 158-159. [张维, 汤国安, 陶旸等. 基于DEM汇流模拟的鞍部点提取改进方法. 测绘科学, 2011, 36(1): 158-159. ]
Based on the analysis of the saddle’s characteristics, extract the feature points by using the mobile window method, then layer the grid DEM data in order to simulate the geomorphic characteristics of contour map. Thus distinguish them by examining the topological relationship with its’ surrounding area. The experimental results show that the algorithm is fast, simple and fit the landform cognition.
1.Xi’an University of Architecture and Technology, Xi’an 710055, China 2.Xi’an Research Institute of Survey and Mapping, Xi’an 710055, China
Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian’e volcanic region of northeastern China, broadly distributed flat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian’e volcanic region by combining DEM analysis and numerical modeling. Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient ( K ) is 1.32×10 -8 , and the best fit drainage area exponent ( m ) is 0.69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian’e volcanic region are ~1-10 mm/a during the early stages of transient incision, and that the present rates are ~1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula (Japan), which have a similar geologic history to the Yalu River-Wangtian’e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian’e volcanic region in northeastern China.
State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
JiangLing, TangGuoan, ZhaoMingwei, et al. Extraction and analysis of loess gully heads considering geomorphological structures. Geographical Research, 2013, 32(11): 2153-2162. [江岭, 汤国安, 赵明伟等. 顾及地貌结构特征的黄土沟头提取及分析. 地理研究, 2013, 32(11): 2153-2162. ]
The gully head is the most active development position in loess landform. The individual and group of gully heads to nibble the loess area between gullies has a marked influence on monitoring the surface erosion and evolution in Loess Plateau. The effective extraction and investigation of gully heads is of critical significance to have a deeper study on the spatial form structure of loess landform systematically. In this paper, three typical landform areas of Loess Plateau are chosen as study areas which are Chunhua, Yijun and Yanchuan. They are located in loess tableland area, loess broken plateau area and loess hilly area respectively, and distributed in the north-south direction of the northern part of Shaanxi province. A gully head extraction model is designed based on 5-m resolution DEMs considering geomorphological structures. In each test area, the spatial information of gully heads is obtained by the extraction model, and the spatial distribution of gully heads is analyzed via the point pattern method. The result of precision evaluation shows that the automatic extraction method considering the shoulder line has 78.7% accuracy on the precision of quantity and 83.4% accuracy on the precision of shape consistent degree. The experiment of the spatial distribution characteristic is completed by the improved point pattern method. The experimental result shows that gully heads gradually approach to the divide line along with the increasing development degree of ravines. And in loess tableland area, loess broken plateau area and loess hilly area, the spatial distributions of gully heads respectively present three statues: clustered far from divide line, random and clustered near divide line. The application example also proves that the spatial distribution characteristic of gully heads is more in line with the actual situation when using the improved method called Area Decomposition Method to convert polygons to points. In conclusion, the research could be valuable not only in deepening the understanding of the spatial pattern of loess landform from the view of gully head, but also in offering a methodological support for digital terrain analysis on Loess Plateau.
1. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing 210023, China; 2. State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 3. University of Chinese Academy of Sciences, Beijing 100049, China
AiTinghua, ZhuGuorui, ZhangGenshou. Extraction of land form features and organization of valley tree structure based on Delaunay Triangulation model. Journal of Remote Sensing, 2003, 7(4): 292-298. [艾廷华, 祝国瑞, 张根寿等. 基于 Delaunay 三角网模型的等高线地形特征提取及谷地树结构化组织. 遥感学报, 2003, 7(4): 292-298. ]
Terrain landform features play major roles in such fields as geomorphology type recognition, relief map generalization, DEM construction and hydrology analysis. This paper presents an automatic method to extract terrain landform features and organize drainage system into tree structure based on bend assessment using Delaunay triangulation model. Compared with traditional DEM or TIN based methods, this pure vector approach obtains not only the topological structure of drainage system in planar graph, but also the valley distribution polygon range. Depending on geometrical computation and judgment of vector line, polygon, the structured properties in drainage representation is enhanced, avoiding the case of noise disturbance in DEM based method. The core algorithm makes use of the ability of Delaunay triangulation in detecting hierarchical structure of each contour line. Three kinds of tree structure organization are discussed: the hierarchical binary tree representing bend inclusion relationship contained in single contour line, the plane structure tree representing valley topological relationship, the semantic hierarchical tree representing valley join level from the point of view of hydrology. This paper gives systemically experiment and detailed comparative analysis.
In this paper, a new method for automatic extraction of ridge and valley axes from DEM, named as Directional Profile Approach(DPA), is proposed. DPA can automatically determine whether a grid point in DEM is a possible ridge(or valley) grid point, according to the features of the profiles through this grid point. Applying this new method to extracting ridge and valley axes automatically from DEM, the following several procedures must be accomplished: First, the all elevation grid points which may be located in ridge and valley lines are automatically recognized with DPA. Then the modified Hilditch thinning algorithm is applied to selecting the ridge and valley grid points recognized by DPA. Third, the every two neighboring ridge points or valley points are connected and rudimentary form of the ridge or valley axes is constructed. Finally, the closed triangles in ridge and valley axes are broken and the short branches are removed. A real DEM was used for testing data, the ridge and valley axes extracted automatically by this method can basically represent the topographic features of the corresponding topographical map. Therefore, this new method is effective.
ZhouYi, TangGuoan, ZhangTing, et al. A new method for the derivation of terrain skeleton lines based on wire-like analysis window in grid DEMs. Bulletin of Surveying and Mapping, 2007, (10): 67-69. [周毅, 汤国安, 张婷等. 基于格网DEM 线状分析窗口的地形特征线快速提取方法. 测绘通报, 2007, (10): 67-69. ]
There are some fast and effective methods related to image processing technique.But they are unsatisfactory in resisting the noise and in reducing the redundant information.For this situation,a new method of extracting terrain feature lines is proposed by the mathematical morphology.Considering the characteristics of the ridges and valleys,two kinds of operators are designed by basic morphological operation.Then the new method is built on the operators with iterative forms.The experimental results show that the ridge-lines and valley-lines extracted by the method fit the real terrain.And it can resist some small-scale noise.
1 School of Information & Control,Xi'an University of Architecture & Technology, 13 Yanta Road,Xi'an 710055,China; 2 Xi'an Research Institute of Survey & Mapping,1 Middle Yanta Road,Xi'an 710054,China; 3 Xi'an Technical Division of Surveying & Mapping,36 Xiying Road,Xi'an 710054,China
A method of the extraction of ridge lines and valley lines from mountainous LIDAR ground point cloud is presented. We extracted the normal vector and curvature of ground data based on differential geometry theory and local polynomial fitting,acquied the ridge points and valley points by computing extremum coefficient of curvature, generated ridge lines and valley lines based on the principle of minimum spanning tree. The results show that the method is feasible and effective.
1)Institute of Surveying and Spatial Information,Chang’an University,Xi’an 710054 2)China J K Institute of Engineering Investigation and Design,Xi’an 710043
LuGuonian, QianYadong, ChenZhongming. Study of automated extraction of shoulderline of valley from grid digital elevation data. Scientia Geographica Sinica, 1998, 18(6): 567-573. [闾国年, 钱亚东, 陈钟明. 基于栅格数字高程模型自动提取黄土地貌沟沿线技术研究. 地理科学, 1998, 18(6): 567-573. ]
The extraction of continuous shoulder line of valley having precise location is the key technique to the construction of spatial distribution mechanism-course models such as soil erosion, sediment transportation and runoff course in gully area in the Loess Plateau. The extraction technique presented in this paper is a morphologically based method utilizing finite morphologic elements to define the topographical structure. In this paper, the authors present an algorithm by which the drainage network and the continuous shoulder line of valley is extracted automatically from the DEM of Wangjiagou in Lishi, Shanxi, which is located in gully area in the Loess Plateau, and the final result is in accordance with the real condition of the experiment area.
Department of Geography, Nanjing Normal University, Nanjing 210097
We propose a new method for extracting loess shoulder-lines from grid DEM.The morphological characteristics of loess shoulder-lines are investigated firstly.By applying the edge detection approach,a new method for extracting loess shoulder-line candidate points is proposed based on the prominent height variation of the points.The algorithm then connects the candidate points to small line segments by morphological methods.Finally,precise,systematic loess shoulder-lines are extracted after refining the line segments.Experiments in the loess hill area show that the extracted lines from gradient based operators,such as Sobel,Roberts and Prewitt,have relatively poor results on both integration and matching precision with manually extracted loess shoulder-lines,while loess shoulder-lines extracted by LOG operator has very good matching ratio to the manually extracted loess shoulder-lines.So LOG is an ideal loess shoulder-lines extraction operator and can be used to extract loess shoulder-lines effectively and automatically.
1 Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University,1 Wenyuan Road,Nanjing 210046,China
ZhouYi, TangGuoan, WangChun, et al. Automatic segmentation of loess positive and negative terrains based on high resolution grid DEMs. Scientia Geographica Sinica, 2010, 30(2): 261-266. [周毅, 汤国安, 王春等. 基于高分辨率 DEM 的黄土地貌正负地形自动分割技术研究. 地理科学, 2010, 30(2): 261-266. ]
China Loess Plateau is world-wide famous for its peculiar and unique landscape, in which the loess shoulder-lines zigzag on the surface making a distinct separation between loess positive terrain and the negative one. The automatic segmentation of loess positive and negative terrains (P-N terrains)with precise location and high efficiency, which is a crucial technique in constructing the mechanism-process models of loess landform drainage systems, is still need to be further improved. Nowadays, with the increasing availability of digital topographic data, the Digital Elevation Model (DEM)can now be applied to better description of natural topography, and it is also regarded as the most proper data source for automatic extraction of loess positive and negative terrains. In this paper, the conformation and flow confluence characteristic of the hill-slope in representative loess landforms is discussed. Based on this, an auto-segmentation method of P-N terrains from 5 m resolution DEMs is proposed. There are three key procedures in the operation. The first step is the identification of grid points on the shoulder-line position by considering the slope difference up and down. Slope gradient 30°,25°and 20°are used as the thresholds in loess platform area, loess ridge-hill area and loess hill area respectively in the extraction model. The second stage is to expand shoulder-lines’candidate cells directionally by considering the spatial direction of the local hill slope aspect and the trend of the shoulder-lines. This step is helpful for deriving more consecutive and detailed shoulder-lines on DEMs. The third step is the generation of positive terrain which can be regarded as the extraction of the upstream area of the shoulder-line points by using the hydrologic analysis model. All the shoulder-lines’cells derived above are imported into the model as the pour point data. This is an alternative method for evading the difficulty of converting shoulder-line grid cells into consecutive vector lines. Validation tests are took out by contrasting the auto-extraction results from DEMs and the delineating results from 1 m resolution DOMs in six drainages. Results show that maximum area difference between the positive terrain area derived above and actural area is 1.15 km 2 , and the percentage of the cells distance offset values less than 10 m exceed 95%. So the main advantages of this approach are high accuracy, lower demands on manual intervention and ready availability of required data for many regions on the Loess Plateau. The morphology of the earth surface is the interactional production of the hydrosphere, lithosphere, atmosphere and the biosphere, thus the morphology is the external representation, and the interaction process is the inner dynamical force. The extraction of the topographic feature lines not only need considering the characteristic of the terrain morphology, but also need considering the inner mechanism of land surface process.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing, Jiangsu 210046; 2. Land Information Engineering Department, Chuzhou University, Chuzhou, Anhui 239012; 3. Institute of RS and GIS, Peking University, Beijing 100871
ZhouY, Tang GA, YangX, et al. Positive and negative terrains on northern Shaanxi Loess Plateau. Journal of Geographical Sciences, 2010, 20(1): 64-76.
The Loess positive and negative terrains (P–N terrains), which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction method from high-resolution Digital Elevation Models. Using 5 m-resolution DEMs as original test data, P–N terrains of 48 geomorphological units in different parts of Shaanxi Loess Plateau are extracted accurately. Then six indicators for depicting the geomorphologic landscape and spatial configuration characteristic of P–N terrains are proposed. The spatial distribution rules of these indicators and the relationship between the P–N terrains and Loess relief are discussed for further understanding of Loess landforms. Finally, with the integration of P–N terrains and traditional terrain indices, a series of un-supervised classification methods are applied to make a proper landform classification in northern Shaanxi. Results show that P–N terrains are an effect clue to reveal energy and substance distribution rules on the Loess Plateau. A continuous change of P–N terrains from south to north in Shaanxi Loess Plateau shows an obvious spatial difference of Loess landforms and the positive terrain area only accounted for 60.5% in this region. The P–N terrains participant landform classification method increases validity of the result, especially in the Loess tableland, Loess tableland-ridge and the Loess low-hill area. This research is significant on the study of Loess landforms with the Digital Terrains Analysis methods.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing 210046, China; 2. Institute of RS and GIS, Peking University, Beijing 100871, China; 3. School of Foreign Languages, Central South University, Changsha 410083, China; 4. College of Land and Resources, China West Normal University, Nanchong 637002, Sichuan, China
ChenYonggang, TangGuoan, ZhouYi, et al. The positive and negative terrain of loess plateau extraction based on the multi-azimuth DEM shaded relief. Scientia Geographica Sinica, 2012, 32(1): 105-107. [陈永刚, 汤国安, 周毅等. 基于多方位 DEM 地形晕渲的黄土地貌正负地形提取. 地理科学, 2012, 32(1): 105-107. ]
Based on the DEM data of Jiuyuangou wateshed in Suide County, Shaanxi of China, with a spatial resolution of 5 m, employing the digital terrain analysis, multivariate statistics and data mining methods, multiple indexes of multi-azimuth DEM shaded relief and slope are established. The solutions of extraction positive and negative terrain of loess plateau by Principle Components Analysis, and Logistic regression model is proposed. The result indicates that: the extracting model has better consistency and accuracy, of which the accuracy is 82.1% and Kappa statistics is 0.6298. Tested on 6 samples of different valley by this model, the mean accuracy of positive and negative terrain are at 77.6% and 84.9%, and weighed mean accuracy is 81.3%. It is suitable to extract positive and negative terrain of loess plateau by PCA and Logistic regression model.
1. Key Laboratory of Virtual Geogrpahic Environment of Ministry of Education,Nanjing Normal University, Nanjing, Jiangsu 210046,China; 2. Zhejiang Provincial Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration, Zhejiang Agriculture and Forestry University, Lin'an, Zhejiang 311300, China
TangGuoan, ZhaoMudan, LiTianwen, et al. Modeling slope uncertainty derived from DEMs in loess plateau. Acta Geographica Sinica, 2003, 58(6): 824-830. [汤国安, 赵牡丹, 李天文等. DEM 提取黄土高原地面坡度的不确定性. 地理学报, 2003, 58(6): 824-830. ]
Slope is one of crucial terrain variables in spatial analysis and land use planning, especially in the Loess Plateau area of China where rugged terrains enhance serious soil erosion. DEM based on slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with their popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10000 scale topographical maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in loess area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas, but their regression coefficients were closely related with the terrain complexity of the test areas. If stream channel density was taken to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels could be expressed as (0.0015S2 + 0.031S - 0.0325)X - 0.0045S2 - 0.155S + 0.1625, with a R 2 value of over 0.98. Practical tests also show an effective result of this model in applications.
1. Department of Urban and Resource Science, Northwest University, Xi'an 710069, China; 2. The Key Open Laboratory of Continental Dynamics, Ministry of Education, Northwest University, Xi'an 710069, China; 3. Institute of Soil and Water Conservation, CAS and Ministry of Water Resources, Yangling 712100, China
Slope spectrum is an original methodology to analyze terrain character of the Loess Plateau.Both1:10,000 DEMs of representative area in Loess Plateau and Qinling Mountains were taken as the test data,from which slope spectrums are derived.With the conception of "ε-band" from spatial data uncertainty,the variation character of different sampling area and position in different test areas were studied.The fundamental conditions of slope spectrum abstraction and application are geomophlogical similarity,rationality of study scale and the integrality of landform types.During the same time,the critical area in which the slope spectrum can exist stably is not only the foundation of derived correct slope spectrum,but also the reflection of the comparability of topographic feature between the local and globe.It makes great significance in many geography studies.
1. Key Laboratory of Virtual Geographic Environment(Nanjing Normal University), Ministry of Education, Nanjing, Jiangsu 210097; 2. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, Sichuan 610041
LiFayuan, TangGuoan, JiaYini, et al. Scale effect and spatial distribution of slope spectrum's information entropy. Geo-Information Science, 2007, 9(4): 13-18. [李发源, 汤国安, 贾旖旎等. 坡谱信息熵尺度效应及空间分异. 地球信息科学, 2007, 9(4): 13-18. ]
48 different landform areas of the Loess Plateau in northern Shaanxi province were selected as test areas with the objective of investigating spatial distribution and scale effect of the slope spectrum’s information entropy (SSIE) based on DEMs. Experimental results show that the SSIE can reflect the terrain complexity to a certain extent. There exits a good power function relation between SSIE and gully density: gully density increases with the increase of SSIE. Spatial distribution of SSIE and loess landform are correlative and the SSIE can be taken as a discriminate factor to identify loess landform.
1. Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing 210097; 2. Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, China; 3. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
A new concept dealing with digital analysis of loess terrain, slope spectrum, is presented and discussed in this paper, by introducing its characteristic, represen-tation and extracting method from DEMs. Using 48 geomorphological units in dif-ferent parts of the loess as test areas and 5 m-resolution DEMs as original test data, the quantitative depiction and spatial distribution of slope spectrum in China’s Loess Plateau have been studied on the basis of a series of carefully-designed experiments. In addition, initial experiment indicates a strong relationship between the slope spectrum and the loess landform types, displaying a potential importance of the slope spectrum in geomorphological studies. Based on the slope spectrums derived from the 25 m-resolution DEM data in whole loess terrain in northern part of Shaanxi, 13 slope spectrum indices were extracted and integrated into a compre-hensive layer with image integration method. Based on that, a series of unsuper-vised classifications was applied in order to make a landform classification in northern Shaanxi Loess Plateau. Experimental results show that the slope spec-trum analysis is an effective method in revealing the macro landform features. A continuous change of slope spectrum from south to north in northern Shaanxi Loess Plateau shows an obvious spatial distribution of different loess landforms. This also proves the great significance of the slope spectrum method in describing the terrain roughness and landform evolution as well as a further understanding on landform genesis and spatial distribution rule of different landforms in the Loess Plateau.
Key Laboratory of Virtual Geographic Environment, Nanjing Normal University, Ministry of Education, Nanjing 210046, China
ZhuShijie, TangGuoan, LiFayuan, et al. Spatial variation of hypsometric integral in the Loess Plateau based on DEM. Acta Geographica Sinica, 2013, 68(7): 921-932. [祝士杰, 汤国安, 李发源等. 基于DEM的黄土高原面积高程积分研究. 地理学报, 2013, 68(7): 921-932. ]
Hypsometric integral is a terrain analysis factor with apparent physical and geomorphologic meanings which could reflect the landform erosion stage and evolution process. As a macroscopic parameter and method in terrain analysis, the applications of hypsometric integral could reveal the quantitative characteristic of landform evolution in catchment scale. In this paper, 5 m resolution DEMs and 3 arc-second resolution SRTM DEMs are used respectively to identify the impact factors of HI and its spatial variation in the Loess Plateau. Firstly, the geomorphologic meaning is discussed and summarized. The effect of DEM resolution and the analysis area in HI calculating is probed. With different DEM resolutions, the HI values derived could keep almost the same. When the area of catchment reaches 10 km 2 , the HI tends to be stable, which is regarded as a critical area for extracting HI in this study. Then, the geomorphic feature HI is proposed and the correlation of each kind of HI is calculated. There exist two feature groups in which the correlation coefficient is rather large. They are respectively catchment HI, positive terrain HI, shoulder line HI and peak HI, ridge line HI, and catchment boundary HI. Finally, the landform division based on HI is created through multiresolution segmentation in loess area. The coupling relationships exist in this division and water & soil loss map, sediment transport value map. The division in this paper refines the original map to a certain extent.
Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing 210023, China
面积高程积分(Hypsometric Integral, HI) 是通过统计流域地表的高程组合信息,从而揭示流域地貌形态与发育特征的重要指标。本文以1:10000 比例尺5 m分辨率DEM数据分析流域面积高程积分计算时的影响因素,以SRTM数字高程模型数据为基本信息源,研究黄土高原重点水土流失区的面积高程积分空间分异特征。研究工作首先讨论并总结了面积高程积分的地学含义,明确了DEM分辨率以及分析面积对于面积高程积分计算的影响,并分析各地貌对象面积高程积分的相关性;然后,面向黄土高原重点水土流失区,采用面向多尺度分割的方法,基于小流域面积高程积分,实现了黄土高原重点水土流失区地貌分区。研究结果表明,DEM分辨率对于小流域面积高程积分计算影响较小,当小流域面积阈值达到10 km 2 时,面积高程积分趋于稳定;各地貌对象中,流域面—正地形—沟沿线、山顶点—山脊线—流域边界这两组组内面积高程积分值相关性非常强;基于面积高程积分的地貌分区,与黄土高原地区水土流失分区图和输沙模数分区图具有相当程度的耦合关系,并细化了原有分区结果。
Terrain texture is an important natural texture. DEM based terrain texture attracts more attention in the research area for its purity in representing surface topography and its derivability in terrain analysis. In this paper, 10 sample areas from different landform types of Shaanxi Province were selected to make a quantitative analysis on the terrain texture by Gray level co-occurrence matrix (GLCM) model. Experiments show that, when using the DEM data with 25m resolution, the suitable analytic distance of GLCM model is not less than 3 pixels. Among all the parameters in the model, correlation could be used for texture direction detection. Contrast, variance, and different variance could be applied for texture periodicity analysis. Entropy, angular second moment and inverse different moment are suitable for texture complexity investigation. In this research, quantitative analysis is conducted to terrain texture by using DEM data, hillshade data, slope data and curvature data. The terrain texture directivity experiment shows that the correlation of hillshade data reacts sensitively to the terrain texture direction and can detect main terrain texture direction. The correlation of slope data reacts obviously in rugged topography such as hilly region and mountainous regions so it can play an auxiliary role for hillshade data in the detecting of terrain texture direction. Results of terrain texture periodicity and complexity analysis shows that among DEM data and its derived data, the mean variation coefficient of each texture parameter based on hillshade data is the highest, and it further proves that the hillshade data is most suitable for quantitative analysis of terrain texture. Quantification is conducted by variance of hillshade data to texture periodicity of different terrain texture, variance eigenvalue of flat, platform, hill and mountain region gradually increases which indicates the increase of terrain texture periodicity. Analysis is also conducted to the terrain texture complexity through angular second moment parameters computed by hillshade data. Eigenvalue has clear peak value in the sample region of flat and the eigenvalue of platform decreases obviously. Eigenvalue of hills and mountain region verge to zero which shows that texture of plat has lowest complexity, followed by the lower complexity of platform and the highest complexity of hills and mountain region. This paper also proposed a multi-parameter integrated method which employs both comprehensive periodicity and comprehensive complexity in terrain texture quantitative analysis. This method not only reduces replicate analyses but also makes full use of various texture parameter information, it also unifies range through normalization for the convenience of quantitative analysis. The result showed that these two parameters have significant response to the different terrain texture, which shows a great potential in landform recognition and classification.
1. Key Laboratory of Virtual Geographical Environment, Ministry of Education, Nanjing Normal University, Nanjing 210023, China; 2. Geomatics Center of Jiangsu Province, Nanjing 210013, China
Digital elevation model (DEM) and terrain analysis based on DEM is scale-dependant. With the view of geoscience analysis and modeling, the paper mainly discusses scale and scale effect of terrain analysis based on grid DEM. Firstly, the paper outlines five common uses of the term "scale" within DEM and terrain analysis which are geographical scale, sampling scale, DEM structure scale, analysis scale and cartographic scale. The geographical scale means the spatial extent of the DEM or the area of coverage; the sampling scale refers to sampling intervals in DEM data collection; the DEM structure scale refers to the resolution of DEM which includes DEM horizontal resolution and vertical resolution; the analysis scale refers to the analysis extent of local windows including window size and threshold value; and the cartographic scale which is used for map reflects the ration between the measurements on a map and the actual measurement on the ground. Secondly, the paper's focus is put on the scale effect of terrain analysis based on DEM. In this section, the uncertainty of DEM and terrain analysis caused by the above scales is classified into single scale effect, cross scale effect and boundary effect. One area of terrain analysis that has been largely ignored is the effect of variability of terrain within the bounds of single grid cell that is referred to the heterogeneity effect of DEM grid size in the paper.We pointed out those and discussed the effect on terrain analysis. At the end of this section, the scale threshold which can be used to indicate the effective extend of terrain attributes is discussed. It is known that the existing DEM with fixed resolution does not always meet the requirement of application. This means that one can deduct more scale terrain models from a fixed resolution DEM. In fact, scaling model can realize the terrain information allocation and aggregation in terrain analysis based on DEM. In this paper, three scaling models including scale deduce model, scale inversion model and multi-scale terrain analysis model are discussed.
Key Laboratory of Virtual Geographic Environment,Nanjing Normal University,Ministry of Education, Nanjing 210046, China
WangChun, TangGuoan, LiFayuan, et al. The Uncertainty of slope spectrum derived from grid digital elevation model. Geo-Information Science, 2008, 10(4): 539-545. [王春, 汤国安, 李发源等. 基于 DEM 提取坡谱信息的不确定性. 地球信息科学, 2008, 10(4): 539-545. ]
Slope Spectrum is a new method in geomorphologic research in the Loess Plateau.It can be used to describe not only the spatial variation of loess landform features,but also the rules and the development process of soil erosion in the Loess Plateau.The uncertainty is inherent law of the Slope Spectrum,which directly restricts the application of the Slope Spectrum.The concept and influencing factors of the uncertainty of Slope Spectrum are investigated with the theory and methodology of the geo-information.The Loess Plateau of northern Shaanxi province is taken as a research area.More attentions are paid to the investigation of the key factors affecting the uncertainty of Slope Spectrum,such as scale effect of terrain description based on DEM,classification method,description and modeling and sample area of the slope spectrum.The critical area in which the slope spectrum can exist stably is not only the foundation of extraction corrected slope spectrum,but also the reflection of the comparability of topographic feature between the local and globe.
1. Key Laboratory of Virtual Geographic Environment(Nanjing Normal University), Ministry of Education, Nanjing 210046, China; 2. Land Information Engineering Department, Chuzhou University, Chuzhou 239000, China
In the paper,taking Xiannangou watershed,representing the loess hilly geomorphology landscape,as the test area,a series of hydrologically corrected DEMs with grid cell from 5 m to 200 m were generated using ANUDEM based on the 1∶10 000 digital topographic map.Different resolution slope gradients were extracted within the Arc/Info slope calculation methods.By applying terrain analysis and geostatistical methods,changes of DEM-derived slope with horizontal resolution and their spatial distribution were systematically investigated,both on point,line and surface level.Research shows that with DEM resolution decreasing,slope at single point shows uncertainty,while points at the same slope level change regularly-low slope terrain increases at first and then decreases,middle slope terrain shows slight changes,and steep slope terrain decreases with logarithm greatly.
1 College of Resources and Environment,Northwestern A&F University,3 Taicheng Road,Yangling 712100,China; 2 College of Urban and Environmental Science,Northwest University,1 Xuefu Road,Xi'an 710069,China; 3 Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,26 Xinong Road,Yangling 712100,China
Terrain parameters,such as slope and aspect,are the most frequently surface geomorphic parameters in terrain analysis,hydrological modeling,environmental studies and other geosciences fields.Currently,these terrain parameters are often estimated by 3×3 local moving window at grid-based digital elevation model(DEM);and the estimated value is set to the centre cell in 3×3 window.In other words,the slope/aspect map derived from DEM is the same resolution as the DEM.There exists a question in this observation whether the resolution of slope/aspect map is the same as the DEM resolution or not? Based on the vector algebra and real DEM,it demonstrates that the slope/aspect estimated by 3×3 window is larger than a grid cell of DEM,which is 1.7 to 2.7 times of DEM resolution.
1 Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University, 1 Wenyuan Road,Nanjing 210046,China
YangX, Tang GA, Xiao CC, et al. The scaling method of specific catchment area from DEMs. Journal of Geographical Sciences, 2011, 21(4): 689-704.
Specific Catchment Area (SCA) is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environment. However, SCA value changes significantly at different DEM resolutions, which inevitably affect terrain analysis results. SCA can be described as the ratio of Catchment Area (CA) and DEM grid length. In this paper, the scale effect of CA is firstly investigated. With Jiuyuangou Gully, a watershed about 70 km 2 in northern Shaanxi Province of China, as the test area, it is found that the impacts of DEM scale on CA are different in spatial distribution. CA value in upslope location becomes bigger with the decrease of the DEM resolution. When the location is close to downstream areas the impact of DEM scale on CA is gradually weakening. The scale effect of CA can be concluded as a mathematic trend of exponential decline. Then, a downscaling model of SCA is put forward by introducing the scale factor and the location factor. The scaling model can realize the conversion of SCA value from a coarse DEM resolution to a finer one at pixel level. Experiment results show that the downscaled SCA was well revised, and consistent with SCA at the target resolution with respect to the statistical indexes, histogram and spatial distribution. With the advantages of no empirical parameters, the scaling model could be considered as a simple and objective model for SCA scaling in a rugged drainage area.
1. Key Laboratory of Virtual Geographic Environment, Nanjing Normal University, Ministry of Education, Nanjing 210046, China; 2. Institute of Remote Sensing and Geographic Information System, Peking University, Beijing 100871, China
ZhangW, Montgomery DR. Digital elevation model grid size, land scape representation, and hydrologic simulations. Water Resour. Res. , 1994, 30(4): 1019-1028.
> High-resolution digital elevation data from two small catchments in the western United States are used to examine the effect of digital elevation model (DEM) grid size on the portrayal of the land surface and hydrologic simulations. Elevation data were gridded at 2-, 4-, 10-, 30-, and 90-m scales to generate a series of simulated landscapes. Frequency distributions of slope (tan B ), drainage area per unit contour length ( a ), and the topographic index ( a /tan B ) were calculated for each grid size model. Frequency distributions of a /tan B were then used in O'Loughlin's (1986) criterion for predicting zones of surface saturation and in TOPMODEL (Beven and Kirkby, 1979) for simulating hydrographs. For both catchments, DEM grid size significantly affects computed topographic parameters and hydrographs. While channel routing dominates hydrograph characteristics for large catchments, grid size effects influence physically based models of runoff generation and surface processes. A 10-m grid size provides a substantial improvement over 30- and 90-m data, but 2- or 4-m data provide only marginal additional improvement for the moderately to steep gradient topography of our study areas. Our analyses suggest that for many landscapes, a 10-m grid size presents a rational compromise between increasing resolution and data volume for simulating geomorphic and hydrological processes.
LinKairong, GuoShenglian, XiongLihua, et al. The impact of DEM resolution on TOPMODEL simulation uncertainty. Journal of Natural Resources, 2010, 25(6): 1022-1032. [林凯荣, 郭生练, 熊立华等. DEM栅格分辨率对TOPMODEL模拟不确定性的影响研究. 自然资源学报, 2010, 25(6): 1022-1032. ]
The hydrological uncertainty is one of the most important aspects in hydrological science research. This paper focuses on how resolution impacts the hydrological uncertainty using the TOPMODEL model based on the topographic index, which extracts from DEMs of different resolutions in the Hanjiang River. Three geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1∶50000 scale topographical maps. Hydrological uncertainty was assessed synthetically by using the multiple-objectives fuzzy optimal method. It is found from the analysis on different spatial resolutions that the topographic characteristics parameters of river basin are affected by DEM resolution remarkably, so as to affect the hydrological uncertainty, but this effect is not very great due to the hydrological complexity, and 200 m should be the more suitable grid size for hydrological uncertainty in this area. The integrated method of assessing hydrological uncertainty is a new throughway to study the various hydrological uncertainties.
1. School of Geographical Science and Planning, Sun Yat-sen University, Guangzhou 510275, China; 2. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; 3. China Institute of Water Resources and Hydropower Research, Beijing 100044, China
WuS. , LiJ. , HuangG. An evaluation of grid size uncertainty in empirical soil loss modeling with digital elevation models. Environ Model Assess, 2005, 10(1): 33-42.
This paper presents a study on the effect of topographic variability on grid-based empirical estimation of soil erosion and sediment transport with raster geographic information systems (GIS). An original digital elevation model (DEM) of 10 m resolution for a case watershed is resampled to six realizations of greater grid sizes for a comparative examination. The Universal Soil Loss Equation (USLE) and a distance-based sediment delivery equation are applied to the watershed to calculate soil loss from each cell and total sediment transport to streams, respectively. The results suggest that the selection of the DEM gird size has considerable influence on the soil loss estimation with the empirical models. The estimate of total soil loss from the watershed decreases significantly with the increasing DEM cell size as the spatial variability is reduced by the cell aggregation. The empirical modeling approach is a useful tool for qualitative assessment of soil erosion, provided that spatial variability can be adequately represented by applied DEMs. However, discretion is suggested for its applications to quantitative estimation of soil loss concerning the sensitivity to the grid size selection.
1.Department of Agriculture 4246 Albert Street, Suite 413 Regina Saskatchewan S4S 3R9 Canada 2.Geomatics Engineering Ryerson University Toronto Ontario M5B 2K3 Canada 3.Environmental Systems Engineering University of Regina Regina Saskatchewan S4S 0A2 Canada
MaJianchao, LinGuangfa, ChenYoufei, et al. The effect of terrain heterogeneity on topographic wetness index. Journal ofGeo-Information Science, 2011, (2): 157-163. [马建超, 林广发, 陈友飞等. DEM栅格单元异质性对地形湿度指数提取的影响分析. 地球信息科学学报, 2011, (2): 157-163. ]
The Topographic Wetness Index (TWI) is frequently used to simulate the soil moisture conditions in a watershed quantitatively. The index that extracted from DEM is an important factor with explicit physical significance in the rainfall-runoff process models. Some previous studies discovered that the TWI would change with the resolution of DEM from which it was derived and this change, and terrain heterogeneity of DEM grids were employed to explain the scale dependency. In this paper, we explored the resolution effects of TWI and the influence of terrain heterogeneity of DEM grids. The research area is located in Xiyuanxi watershed, Xiamen City of Fujian Province, which includes different terrain types such as hill, platform, plain, etc. A fine-resolution DEM with 2.5m grid size was used to investigate the scale dependency of TWI values when converting DEM with resolution of 20m. Four terrain and heterogeneity attributes were employed as the quantitative indices of terrain heterogeneity of DEM grids, i.e. standard deviation of elevation, relief, landscape fragmentation index and landscape diversity index. The correlation and regression analysis was performed to identify sensitive and correlative responses between each terrain heterogeneity index and TWI variance as resolution was changed. The results indicated significant negative correlations between the terrain heterogeneity indices and the TWI variance (the Pearson correlation coefficients were -0.707, -0.712, -0.779 and -0.841 respectively, all based on a high confidence level of 0.01). By extrapolating the fitted curve for the terrain heterogeneity indices and TWI variance, the logarithmic curves fit the optimal equations well (the coefficient of determination are all greater than 0.9, F>F 0.01 ). So, these indices can be used to evaluate the impact of the terrain heterogeneity on the TWI. Meanwhile, the regression models can improve the accuracy of the TWI derived from a coarse resolution DEM. The effect discussed in this study is helpful in providing a more accurate data for the TWI applications.
1.College of Geography, Fujian Normal University, Fuzhou 350007, China; 2.Fujian Provincial Engineering Research Center for Monitoring and Assessing Terrestrial Disasters, Fuzhou 350007, China
TangGuoan, ZhaoMudan, LiTianwen, et al. Modeling slope uncertainty derived from DEMs in Loess Plateau. Acta Geographica Sinica, 2003, 58(6): 824-830. [汤国安, 赵牡丹, 李天文等. DEM提取黄土高原地面坡度的不确定性. 地理学报, 2003, 58(6): 824-830. ]
Slope is one of crucial terrain variables in spatial analysis and land use planning, especially in the Loess Plateau area of China where rugged terrains enhance serious soil erosion. DEM based on slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with their popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10000 scale topographical maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in loess area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas, but their regression coefficients were closely related with the terrain complexity of the test areas. If stream channel density was taken to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels could be expressed as (0.0015S2 + 0.031S - 0.0325)X - 0.0045S2 - 0.155S + 0.1625, with a R 2 value of over 0.98. Practical tests also show an effective result of this model in applications.
1. Department of Urban and Resource Science, Northwest University, Xi'an 710069, China; 2. The Key Open Laboratory of Continental Dynamics, Ministry of Education, Northwest University, Xi'an 710069, China; 3. Institute of Soil and Water Conservation, CAS and Ministry of Water Resources, Yangling 712100, China
YangD, HerathS, MusiakeK. Spatial resolution sensitivity of catchment geomorphologic properties and the effect on hydrological simulation. Hydrol Process, 2001, 15(11): 2085-2099.
1 Department of Civil Engineering, University of Tokyo, 7-3-1 Hongo, Bunkgo-Ku, Tokyo 113-8656, Japan 2 Institute of Industrial Science, University of Tokyo, Meguro-Ku, Tokyo 153-8505, Japan * Department of Civil Engineering, University of Tokyo, 7-3-1 Hongo, Bunkgo-Ku, Tokyo 113-8656, Japan
DEM(digital elevation model) and terrain analysis based on DEM are scale-dependant.DEM scale transition that deducting other more scales from a fixed resolution is always met in application such as hydrology,soil science,and geomorphology.We present a new DEM scale transition with point spread function which is of image blur.The presented method is carried out by the spatial convolution between DEM with fixed resolution and simulated point spread functions with different radiuses.Then elevation statistics,contour-matching,and autocorrelation are designed to evaluate the transformed DEM.Finally the results achived with the proposed method were compared with the results of nearest neighbor assignment,bilinear interpolation and cubic convolution in the two different study areas.The result shows that the proposed method is effective.
1 Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University,1 Wenyuan Road,Nanjing 210046,China
HuXuemei, QinChengzhi. Effects of different topographic attributes on determining appropriate DEM resolution. Progress in Geography, 2014, 33(1): 50-56. [呼雪梅, 秦承志. 地形信息对确定DEM适宜分辨率的影响. 地理科学进展, 2014, 33(1): 50-56. ]
Due to the scale effect of changing resolution for grid-based digital terrain analysis, it is important to determine an appropriate resolution (or a range of appropriate resolutions) for gridded digital elevation model (DEM) in practice. The commonly-used approach to determining appropriate resolutions is based on a scale effect curve characterized by certain types of statistics (the mean of local variance is commonly used), which is calculated on the multi-resolution dataset of a specific topographic attribute derived from the gridded DEMs with a series of spatial resolutions. The resolution with the highest value of the mean of local variance is considered to be an appropriate DEM resolution. Although several topographic attributes (such as slope gradient and curvature) have been used in this approach, there are few researches on the effects of different topographic attributes on the results from this approach. In this paper, we used an experiment to compare the effects of three types of topographic attributes (i.e., slope gradient, profile curvature, and horizontal curvature) applied to determining appropriate DEM resolutions. The experiment was conducted in three study areas with different terrain conditions, i.e. Xuancheng area with low relief, Coweeta area with high relief, and Kaixian area with more complex terrain conditions. The tested topographic attributes were calculated from the DEMs with a series of spatial resolutions (i.e., 5, 10, 15, 20, 25, 30, 50, 100, 150, 200, 300 m). For each topographic attribute, two widely-used algorithms were tested. One is proposed by Wood (1996), and the other is the one implemented in Arc-GIS software. The appropriate DEM resolution for a study area had the highest value of the mean of local variance derived from each tested topographic attribute, respectively. Experimental results showed that the effects of slope gradient and curvature are different on the results of the appropriate DEM resolution, while there is little difference between the results from profile curvature and horizontal curvature. The appropriate resolutions based on slope gradient information (i.e., 15, 50, and 100 m for Xuancheng area, Kaixian area, and Coweeta area, respectively) are coarser than those based on curvature information (i.e., 5, 10~15, and 5 m for Xuancheng area, Kaixian area, and Coweeta area, respectively), while the difference between them is less for the study areas with low relief. When slope gradient information was used, the appropriate resolution results for the study area with high relief are coarser than those for the area with low relief. When curvature information was used, the appropriate resolution results for the study areas with simple terrain conditions (such as Xuancheng area with low relief, and Coweeta area with high relief) are finer than those for the study area with complex terrain conditions. The range of appropriate resolutions from each topographic attribute for the study areas with simple terrain conditions is much wider than that for the study areas with complex terrain conditions. For each specific topographic attribute there is no difference between the effects of the tested algorithms of topographic attribute on the results of appropriate resolutions.
1. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China
基于小波多分辨率分析原理,给出了一种尺度依赖的地表形态抽象与表达方法。基于该方法研究了多尺度的地貌自动综合,提出了利用小波系数的范数比作为衡量相应尺度综合程度的数量化指标,并结合实例予以说明。 Abstract: With the development of GIS application ceaselessly, a mass of multi-scale geospatial data need to be analyzed and represented because users require different detailed spatial data to dealwith different problems and output maps at different scales. It has become one of the key problemsto applied GIS. The logic relations have to be established between spatial data sets at differentscales so that one representation of spatial data can be transferred to another completely. The completeness refers that spatial precision and characteristics and a high information density that adaptsto relevant abstract detail must be preserved,and the consistency of spatial semantics and spatialrelations have to be maintained simultaneously.In addition, the deriving of new spatial data setsshould be bi-directional on some constraint in GIS, from fine-scale to broad-scale and vice versa.Automatic generalization of geographical information is the core content of multi-scale representation of spatial data, but the scale-dependent generalization methods are far from abundance becauseof its extreme complicacy.Most existing algorithms about automatic generalization do not relate toscale directly or accurately, not forecast and control the generalized effects, and cannot assess theholistic consistency of the generalized results. The rational and quantitative methods and criterionsof measuring the extent of generalization have not still been sought out. Wavelet analysis is a newbranch of mathematics burgeoning at the end of 1980s. It has double meanings simultaneously onprofundity of theory and extent of application. Because it has good local character at both time orspace and frequency field simultaneously, and sample interval of signal can be adjusted automatically with different frequency components, any details of function, such as a sign or image etc., canbe analyzed at any scales by using wavelet analysis. Therefore, wavelet analysis suggests a new solution to the problems mentioned above. The fundamental characteristics of multi-scale spatial datacan be detected and extracted,and represented by a set of wavelet coefficients, then handled andreconstructed, then the optimal representation of the spatial data sets can be got. This paper studies the multi-scale representation and automatic generalization of relief and the quantitative methodand criterion of investigating the extent of generalization based on the above idea. The paper formulates briefly the basic principle of multiresolution analysis (MRA) on wavelet transform atfirst, and describes a model for multi-scale handling of spatial data based on MRA of wavelet. Weknow that subspace at a higher resolution includes completely all information at a lower resolutionfrom the model, so multiple data sets such as Vi, V2,…, VJ may be derived from a basic set ofspatial data V0 at multiple scale by using MRA of wavelet, and the reverse procedure can be implemented completely by reconstructing. The decomposition and reconstruction are very stable.Accordingly, the model not only meets the need of automatic generalization but also is scale-dependent completely. Handling of automatic generalization is reverse based on the model.Two sections,approximation Ajf and detail Dejf, can be produced automatically by MRA of wavelet. The approximation describes the gentle and trend component of the characteristics of data, and the detaildescribes the fast and local one. They represent low and high frequency of data respectively. Whendata sets at scale j are derived from scale j + 1 , the loss of the approximation is Wj because Vj + 1 = Vj Wj and Vj Vj+ 1, described by Deejf. Therefore,{Dej f} represents the detail generalized at stepped down scale. DEM is an abstract model about relief in GIS. The key problem of multi-scale representation of relief is how to derive the DEM at multiple scales. We propose a schemefor a multi-scale representation and generalization of scale-dependent relief based on the abovemodel,which can be represented by a four tuple:MultiGeomorph = {φ(x ),ψ (x), (Vj)j∈z,( Wj )j∈z }. The tuple includes all information about relief representation at multiple scales. It is ananalysis system based on MRA of wavelet, and describes the mechanism about deriving multi-scaleDEM. Furthermore , it is a dynamic system studying the rule about state of data changing withscale. Therefore,We can get the multi-scale DEM from the MultiGeomorph, the size of the sequence DEMs derived is 2-ktimes of its original, and the relevant scale is stepped down a alf. Withthe scale decreased,the fine characteristics of relief are reduced and filtrated down step by step,but the main characteristics are represented. So the detail extent of relief represented changes withscale.The practical examples are demonstrated in Fig. 1. Model generalization is foundation forcartographical generalization based on DEM. As a result, it is more adapted to analysis and application of GIS,and avoids the harmonization between group contours, which is very difficult for themethods based on contour generalization. The precondition of generalization is derivative of multiscale DEM. The generalization can be considered as a procedure of information reducing on certanconditions. Using MRA of wavelet will erase the topographic points and details, which are minimum contribution for constructing topographical surface. For example, Figs. 2 and 3 demonstratethe original contour map and the generalized counterpart.Assuming { C-J } represents the coefficients of wavelet that include all information after MRA of wavelet, their energy is norm ‖ CJ ‖ .If { CP } represents the wavelet coefficients after generalized, norm ‖ CP ‖ is their energy. Accordingly, the percentage of ‖ CP ‖ to ‖ C-y ‖ can measure the detail extent between the original data sets and their counterparts derived.
Digital Elevation Model(DEM) finds its widely using in the areas of Geography, landscape and regional planning. The abbreviation DEM is used to describe a digital data set which is used to model a topographic surface (a surface representing height data). Since this is impossible, a surface model approximates a continuous surface using a finite number of observations. In its simplest form a vector DEM mimics the raster version by using a regularly spaced set of spot heights to represent the terrain surface. A more advanced, more complex and more common form of vector DEM is the triangulated irregular network (TIN). In vector GIS a TIN is used to create a DEM from either regular or irregular height data. However, some systems have their different request of the data volume under different scale for the influence on the speed of operation and analysis. Besides, cartography generalization of the contour can be realized by the generalization of DEM. So the generalization model on DEM grid data is given in this paper by using the multi band wavelet analysis, and a case study is put forward to give the detail explanation. Meantime, its reliability is described from the point of data volume, profile of the elevation and change of curve surface area.
Chang ZQ, Jia EH, Wu LX. Key technique in compressing grid DEM data with discrete wavelet transform. Journal of System Simulation, 2008, 20(15): 3955-3961.
DEM数据具有不稳定、相关性差的特点,用离散小波变换对格网DEM数据进行压缩处理时,其边界问题将更为突出,主要表现在边界失真非常严重.这种现象不可避免地导致重建DEM数据精度的损失严重.为了最大限度地减弱边界问题的影响、提高压缩比,在进行格网DEM数据压缩时,作者将二维离散小波变换的边界问题转换为一维离散小波变换的边界问题,大大减小了边界失真区域,提高了重建DEM数据的精度.进而,用相应的算法进行了DEM压缩实验, 结果表明:可获取高压缩比且高精度的重建DEM数据. Abstract: Due to the instability and less relativity of DEM data, the boundary problem in discrete wavelet transform becomes more outstanding and kittle when compressing grid DEM data with DWT, which mainly indicates the distortion degree appears very severe. This phenomenon will inevitably lead to serious loss of the precision of reconstructed DEM data. In order to utmost weaken the influence of boundary problem and improve the compression ratio, the boundary problem of two-dimensional DWT was transformed into the boundary problem of one-dimensional DWT, which can enormously diminish the area of boundary distortion and greatly improve the precision of the reconstructed DEM data, then the corresponding algorithm was proposed. Moreover, according to the algorithm, some experiments were made. The results prove that not only higher compression ratios but also reconstructed DEM data with high precision are achieved.
FeiLifan, HeJin, MaChenyan, et al. Three dimensional Douglas-Peucker algorithm and the study of its application to automated generalization of DEM. Acta Geodaetica et Cartographica Sinica, 2006, (3): 278-284. [费立凡, 何津, 马晨燕等. 3维Douglas-Peucker算法及其在DEM自动综合中的应用研究. 测绘学报, 2006, (3): 278-284. ]
Abstract The quality and accuracy of remote sensing instruments have been improved significantly, however, rapid processing of large-scale remote sensing data becomes the bottleneck for remote sensing quantitative retrieval applications. The remote sensing quantitative retrieval is a data-intensive computation application, which is one of the research issues of high throughput computation. The remote sensing quantitative retrieval Grid workflow is a high-level core component of remote sensing Grid, which is used to support the modeling, reconstruction and implementation of large-scale complex applications of remote sensing science. In this paper, we intend to study middleware components of the remote sensing Grid – the dynamic Grid workflow based on the remote sensing quantitative retrieval application on Grid platform. We designed a novel architecture for the remote sensing Grid workflow. According to this architecture, we constructed the Remote Sensing Information Service Grid Node (RSSN) with Condor. We developed a graphic user interface (GUI) tools to compose remote sensing processing Grid workflows, and took the aerosol optical depth (AOD) retrieval as an example. The case study showed that significant improvement in the system performance could be achieved with this implementation. The results also give a perspective on the potential of applying Grid workflow practices to remote sensing quantitative retrieval problems using commodity class PCs. Highlights ? High throughput cluster with community PCs. ? Middleware for the workload balance. ? Dynamic workflow composition and management. ? Vast amount remote sensing data processing.
After analyzing the advantages/disadvantages of distributed memory programming model in cluster environment and shared memory programming model in multi-core CPU respectively,a parallel method,combining clustering and multi-core,is proposed to enhance the strengths and eliminate the weaknesses.Then the relevant parallel algorithms of extracting contours are studied,of which establishing TIN-Mesh and tracking contours are as study cases of parallel shared memory.At last,the feasibility of the parallel method is verified by experiments.
1.Computer Engineering College,Jimei University,Xiamen,Fujian 361021,China 2.School of Remote Sensing and Information Engineering,Wuhan University,Wuhan 430079,China 3.China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China
HuangF, LiuD, TanX, et al. Explorations of the implementation of a parallel IDW interpolation algorithm in a Linux cluster-based parallel GIS. Computers & Geosciences, 2011, 37(4): 426-434.
Abstract To design and implement an open-source parallel GIS (OP-GIS) based on a Linux cluster, the parallel inverse distance weighting (IDW) interpolation algorithm has been chosen as an example to explore the working model and the principle of algorithm parallel pattern (APP), one of the parallelization patterns for OP-GIS. Based on an analysis of the serial IDW interpolation algorithm of GRASS GIS, this paper has proposed and designed a specific parallel IDW interpolation algorithm, incorporating both single process, multiple data (SPMD) and master/slave (M/S) programming modes. The main steps of the parallel IDW interpolation algorithm are: (1) the master node packages the related information, and then broadcasts it to the slave nodes; (2) each node calculates its assigned data extent along one row using the serial algorithm; (3) the master node gathers the data from all nodes; and (4) iterations continue until all rows have been processed, after which the results are outputted. According to the experiments performed in the course of this work, the parallel IDW interpolation algorithm can attain an efficiency greater than 0.93 compared with similar algorithms, which indicates that the parallel algorithm can greatly reduce processing time and maximize speed and performance.
Digital elevation model(DEM) are collections of elevation points and could be used to describe the geographical features and to show the terrain surface in three dimensions over a certain area. This features are more important for various applications. DEMs are created by collecting elevations and referencing them to corresponding points in the mapped area. The elevations add a Z value to the ground's X and Y horizontal coordinates. However, it is always more difficult to get DEM and normally needs more computing time to generate DEM since its complicated algorithm and huge data. In order to speed up the generating of DEM, this paper makes some sensitive study on the parallel processing of the interpolation of DEM. Based on the analyzing of several common interpolation methods of DEM, the linear interpolation (sometimes called Proportional Distance Method) was chosen as our basic algorithm. Meanwhile, data parallel and algorithm parallel approaches were applied to this basic algorithm. Through the experiences at networked parallel processing system some good results were obtained and proposal for further research on this topic was provided.
QiLin, ShenJie, GuoLishuai, et al. Dynamic strip partitioning method oriented parallel computing for construction of Delaunay triangulation. Journal ofGeo-Information Science, 2012, 14(1): 55-61. [齐琳, 沈婕, 郭立帅等. 面向D-TIN并行构建的动态条带数据划分方法与实验分析. 地球信息科学学报, 2012, 14(1): 55-61. ]
Data partitioning is an important step of parallel algorithm design. The load balance and efficiency of data partitioning is the precondition for improvement of parallel algorithm efficiency. For aggregated distributed point sets, the traditional Delaunay triangulation parallel algorithm can't ensure the balance and the execution's efficiency of the partitioning result. In view of the problems above, this paper we proposed a partitioning method using dynamic strips based on the idea of equally strips partitioning method in traditional Delaunay Triangulation construction and we titled it Dynamic Strip Partitioning Method. The detailed steps of this algorithm are as follows. First, the minimum bounding rectangle of the point data set should be obtained and the point set is roughly split using regular slim strips in the same direction. Then the number of points in every strip would be counted and the neighbor strips are merged into a partition region from the first strip in the sequence following a certain regulation. The boundaries of some strips should be moved dynamically if the total amount of points in these strips reached the load threshold value. In order to promote the efficiency of partitioning and reduce the boundaries movement, a rule of "move half points a time" has been used. We tested the speed-up of the Delaunay Triangulation parallel algorithm using the artificial point sets and tested the performance of the Delaunay triangulation parallel algorithm using the real test area point sets in the multi-kernel parallel computing systems. The results of the experiments showed that the method of dynamic strips partitioning can help to get high and stable speed-up of the Delaunay triangulation parallel algorithm and the data distributional pattern and size has less influence to it. Delaunay triangulation parallel algorithm based on dynamic strips partitioning method can get high efficiency and the speed-up effect is superior to the traditional method.
1. School of Geographic Science, Nanjing Normal University, Nanjing 210046, China; 2. Key Laboratory of Virtual Geographic Environment, MOE, Nanjing 210046, China; 3. Key Laboratory of Geographic Information Science of Jiangsu Province, Nanjing Normal University, Nanjing 210046, China
Delaunay triangulation reconstruction is a hotspot but hard problem in 3D scene rendering and visualization field. In this paper, a review of Delaunay triangulation development is given, and then three current kinds of Delaunay triangulation methods are summarized: incremental method, triangle expanding method and divide-and-conquer method. Moreover, several kinds of algorithms under the frame of each triangulation method are compared in terms of advantage, disadvantage and complexity. Finally, directions of future work of Delaunay triangulation methods in large-scale scene rendering and terrain visualization field have been discussed, including research on algorithm combination, algorithm supporting technology and distributed parallel algorithm.
Along with the multi-scale digital elevation model (DEM) accomplished in China,the DEM-based spatial analysis plays an increasingly important role in GIS research,and the DEM-based spatial analysis needs high resolution data,which means the increasing demand for density computing.Computational grids can solve the high density computing demand for DEM analysis that involved enormous amounts of data.We demonstrated the feasibility of DEM analysis tools and completed the prototype of the system based on computational grids and designed system architecture based on Alchemi,which is a computational grids framework.The DEM analysis tools can be divided into DEM analysis server,computational grids nodes and spatial database server in architecture.The DEM analysis tools can be implemented in API,grids,spatial analysis and application layers.The Parallel algorithm of the tools is based on the principle of procedure decomposition,functional decomposition and data decomposition.A separate spatial database server is designed as a spatial data server to avoid huge decline in efficiency caused by the mass data transfer in distributed computing grid.The efficiency of computational grids is tested by slope factor calculation based on the prototype system of DEM analysis tools.Experiments show that the efficiency of DEM analysis for big dataset can be significantly enhanced by computational grids,but for small dataset,the efficiency is not significant.The results confirm the feasibility of the application of computational grids to DEM spatial analysis for enormous amounts of data.
1. Graduate School, China University of Geosciences, Wuhan 430074, China; 2. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China; 3. College of Public Administration, Huazhong University of Science and Technology, Wuhan 430074, China
Digital Terrain Analysis (DTA) is a digital information processing technology based on Digital Elevation Model (DEM) for the terrain attribute calculation and features extraction. Slope and aspect are the basic terrain parameters of DTA and widely used in different fields. However, it is always more difficult to get slope and aspect from DEM and normally needs more time to calculate slope and aspect due to large study area and huge data. Based on the analysis of serial algorithm features of slope and aspect in terrain analysis, the strategies of the data division, the data fusion and I/O of DTA algorithms are analyzed, and the parallel method was constructed from the aspect of data parallelism in the paper. The research indicates that the parallel method is efficient in performing the parallelization of sequential algorithms of slope and aspect, and the parallel method increases the execution efficiency of algorithms and achieves a good performance. The proposed parallel method can also be as a reference for the parallelization of the algorithms with the similar matrix type data.
(Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University,Nanjing 210023,China)
High resolution digital elevation models (DEM) used in digital terrain analysis are becoming more and more prevalent. There are various curvilinear structure extracting algorithms, but the main limitation of them is the high computing cost, making them less efficient when extracting topographic feature lines from high resolution DEM images. We propose an efficient strategy to speed them up using Steger's curvilinear structure detection algorithm imple mented on graphic processing units (GPU). We choose to speed up the most computation intensive modules of the algorithm (Hessian matrix generation and feature point detection) using NVIDIA's compute unified device architecture (CUDA). This method can achieve more than five times speedup compared with the original algorithm on central process units (CPU) for large scale DEM images with millions of pixels.
Gong JY, Xie JB. Extraction of drainage networks from large terrain datasets using high throughput computing. Computers & Geosciences, 2009, 35(2): 337-346.
Abstract Advanced digital photogrammetry and remote sensing technology produces large terrain datasets (LTD). How to process and use these LTD has become a big challenge for GIS users. Extracting drainage networks, which are basic for hydrological applications, from LTD is one of the typical applications of digital terrain analysis (DTA) in geographical information applications. Existing serial drainage algorithms cannot deal with large data volumes in a timely fashion, and few GIS platforms can process LTD beyond the GB size. High throughput computing (HTC), a distributed parallel computing mode, is proposed to improve the efficiency of drainage networks extraction from LTD. Drainage network extraction using HTC involves two key issues: (1) how to decompose the large DEM datasets into independent computing units and (2) how to merge the separate outputs into a final result. A new decomposition method is presented in which the large datasets are partitioned into independent computing units using natural watershed boundaries instead of using regular 1-dimensional (strip-wise) and 2-dimensional (block-wise) decomposition. Because the distribution of drainage networks is strongly related to watershed boundaries, the new decomposition method is more effective and natural. The method to extract natural watershed boundaries was improved by using multi-scale DEMs instead of single-scale DEMs. A HTC environment is employed to test the proposed methods with real datasets.
Visualizing and analyzing the explosive datasets coming from observation and simulation in the geosciences is becoming great challenge. Using parallel visualization technique to visualize the large-scale geosciences data is an effective solution. We discuss the usage of large-scale data parallel visualization in the geosciences in the paper. We firstly introduce the several parts of large-scale data parallel visualization, then characterize the features of large-scale data of geosciences, at last, we discuss the usage of parallel visualization of large-scale data in the visualizing simulation results of mantle convection, seismic wave propagation and tsunami.
Laboratory of Computational Geodynamics, Graduate University of the Chinese Academy of Sciences, Beijing, P. R. China, 100049
DEM data is organized in blocks and scheduled with cache. An algorithm based on LoD is implemented with multi core CPU for simplifying the terrain triangulation network dynamically during rendering process. The terrain model is divided into pieces so that the rendering process for each piece can be implemented in parallel. An experimental system based on parallel rendering algorithm is developed, with OpenMP and OpenThreads. The results show that the rendering performance of the 3D DEM system is improved efficiently based on parallel algorithm as compared with traditional algorithm.
1 Department of Geographic Information Science,Nanjing University, 22 Hankou Road, Nanjing 210093, China ; 2 Land and Resources Information Center of Jiangsu Province, 47 Sipailouxiang, Nanjing 210029, China ; 3 Jiangsu Surveying and Mapping Engineering Institute, 75 West Beijing Road, Nanjing 210031, China
采用数据分块进行地形数据组织,基于缓存策略进行数据调度,对各地形块采用四叉树LoD(level of detail)的细节简化算法,利用多核CPU的计算特性实现四叉树LoD的并行生成,在动态构造地形三角网后,让不同的CPU核心负责不同地形区域以实现并行渲染,基于OpenMP及OpenThreads建立原型系统。实验结果表明,并行化渲染具有明显的性能优势。
XiongLiyang, TangGuoan, YuanBaoyin, et al. Geomorphological Inheritance for loess land form evolution in a severe soil erosion region of Loess Plateau of China based on digital elevation models. Science China: Earth Sciences, 2014, 57(2): 313-321. [熊礼阳, 汤国安, 袁宝印等. 基于 DEM 的黄土高原 (重点流失区) 地貌演化的继承性研究. 中国科学: 地球科学, 2014, 57(2): 313-321. ]
Based on the drilling data of the Upper Ordovician Wufeng Shale and the Lower Silurian Longmaxi Shale in southern Sichuan Basin, the construction of matrix pores and the development condition of fractures in a marine organic-rich shale are quantitatively evaluated through the establishment of the reservoir petrophysical models and porosity mathematical models. Our studies show that there are four major characteristics of the Longmaxi Shale confirmed by the quantitative characterization: (1) the pore volume of per unit mass is the highest in organic matter, followed in clay minerals, finally in brittle minerals; (2) the porosity of the effective shale reservoir is moderate and equal to that of the Barnett Shale, and the main parts of the shale reservoir spaces are interlayer pores of clay minerals and organic pores; (3) the porosity of the organic-rich shale is closely related to TOC and brittle mineral/clay mineral ratio, and mainly increases with TOC and clay mineral content; (4) fractures are developed in this black shale, and are mainly micro ones and medium-large ones. In the Longmaxi Shale, the fracture density increases from top to bottom, reflecting the characteristics with high brittle mineral content, high Young's modulus, low Poisson's ratio and high brittleness at its bottom.
1 Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China; 2 Geophysics and Oil Resource Institute, Yangtze University, Jingzhou 434023, China; 3 Exploration and Development Research Institute, PetroChina Southwest Oil & Gasfield Company, Chengdu 610051, China; 4 Earth and Space Sciences Institute, Peking University, Beijing 100871, China
LiuYong, WangYixiang, PanBaotian. A preliminary approach on the 3D presentation and quantitative analysis of planation surface. Geographical Research, 1999, 18(4): 391-399. [刘勇, 王义祥, 潘保田. 夷平面的三维显示与定量分析方法初探. 地理研究, 1999, 18(4): 391-399. ]
Planation Surface is one of the very important issues in the field of current geomorphology, and plays a major role for reconstructing the evolutional history of land from in a region. By using remote sensing and geographical information systems, this article discussed the creation of the Digital Elevation Model(DEM) of the Meiwu Plateau, at the south of Lanzhou and the northeastern margin of the Qinghai-Xizang Plateau, and the integration of both DEM and Landsat TM images. Then the characteristics of 3D Geomorphological Imagery of the Meiwu Plateau were discussed, and the topographic profiles at several parts of the DEM were got. On the basis of analyzing the system of geomorphological parameters on the planation surface, the exact extent of the planation surface on the Meiwu Plateau was got by using the supervised classification technique in the field of image processing. The great potential of this technique was discovered on the analysis of planation.
Department of Geography, Lanzhou University, Lanzhou 730000, China
Choosing scientific method to extract and express relief amplitude has become the critical factor to improve the effectiveness and practicality in relief research.Based on SRTM3-DEM,the relief amplitude with increasing grid window method in the Tibetan Plateau was extracted,and then the best window area by the mean change point method was calculated.The result shows that 1.17km 2 could be the best window area,the relief amplitude can be divided into eight classes,and the most widely distributed class is low rolling mountain.The relief amplitude is generally more violent at the edge of the plateau.It is mainly due to the intensive tectonic movement and river headward erosion.While the terrain is relatively flat in hinterland of the plateau,the erosion and removal caused by glaciation and unfreezing may be the greater impact on the relief amplitude.
Xi'an Center of China Geological Survey, Xi'an, Shaanxi 710054, China
以青藏高原区域大尺度SRTM3-DEM为数据源,运用GIS的窗口递增分析法依次计算2×2、3×3、4×4、5×5、…、32×32窗口下的地势起伏度,然后采用均值变点法科学的分析平均地势起伏度的最佳统计面积并进行分级分析,得出实验区最佳分析窗口面积为1.17 km 2 ,地势起伏度可分出八级,其中小起伏山地分布最广。高原边缘的地势起伏度普遍较大主要是由于构造运动与河流朔源侵蚀作用强烈;而高原内部地势较为平缓,冰川、冻土作用下的侵蚀搬运可能对地势起伏的影响更大。
ZhangHuiping, YangNong, ZhangYueqiao, et al. Geomorphology of the Minjiang drainage system (Sichuan, China) and its structural implications. Quaternary Sciences, 2006, (1): 126-135. [张会平, 杨农, 张岳桥等. 岷江水系流域地貌特征及其构造指示意义. 第四纪研究, 2006, (1): 126-135. ]
Compared with the remarkably flat feature of the main body of the Tibetan Plateau, geomorphology of the peripheral areas varies greatly. As an example, the eastern margin of Tibetan Plateau is more diffuse and irregular than the northern and southern ones. The Minshan Mountain along with its adjacent regions form a series of escarpments, become one of the key continental escarpments. The Minjiang drainage basin is part of this series and is adjacent to the Sichuan Basin. Knowledges of the geomorphic features of the Minjiang drainage networks and drainage sub-basins, of the stream morphology and the morphometric relation between the slope and elevation of the Minjiang drainage basin are still lacking.The recently developed digital elevation model (DEM) makes it possible to rapidly quantify the topographic characteristics of areas ranging from local drainage basins to entire continents. A DEM-based topographic analysis of mountain belts have been recently carried out along cross-sections perpendicular to the main structures of different orogens, which has shown that the Minjiang drainage basin has distinct geomorphic characteristics. Results from SRTM-DEM-determined Minjiang drainage sub-basins and channel profiles have shown that the eastern and western tributaries of the Minjiang River are obviously asymmetric. Almost all the analyzed characters (such as the areas, perimeters and total channel lengths) of the eastern sub-basins (except 32 # ,46 # and 58 # ) are smaller that those of the western ones. Areas and perimeters of most the western sub-basins are more than 100km 2 and 100km respectively and the area of 15 # sub-basin even reaches up to 7202km 2 or so. The total channel lengths within many western sub-basins are above 200km. Besides the above features, the eastern streams show a little lower bifurcation ratios within 3.0~4.0; however, these parameters of the western ones are almost between 4.1~5.0.Longitudinal channel profiles of western and eastern 5 th order streams indicate that the lengths of the longest channels within almost all the eastern sub-basins are less than 20km, but those of western ones are normally more than 20km. The relative higher drops and gradients presented by eastern longest streams show the existence of the higher incision rate along this region.Taking it into account that the same outcropping and climate conditions control the whole Minjiang drainage basin, it can be concluded that lower perimeter and area of drainage sub-basins, total channel length, bifurcation ratio and higher channel gradient within eastern sub-basins along the Minjiang mainstream maybe result from the differential uplift of the Minshan Mountain region within Late Cenozoic. The shorter streams and lower bifurcation ratios maybe indicate the undergrowth and newborn features of these eastern streams, which are also representative for the eastern uplift of the Minshan Mountain.
①State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083,China; ②School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083; ③Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081; ④Department of Earth Sciences, Nanjing University, Nanjing 210093; ⑤Institute of Geological Environment Measurement,Beijing 100081
GaoMingXin, LiuShaofeng. Pleistocene paleosurface reconstruction and Holocene erosion quantity calculation for Guide-Gonghe-Tongde basin complex, Qinghai. Remote Sensing for Land and Resources, 2013, 25(1): 99-104. [高明星, 刘少峰. 青海贵德—共和—同德地区更新统最小古沉积面恢复与全新世侵蚀量计算. 国土资源遥感, 2013, 25(1): 99-104. ]
The Guide- Gonghe-Tongde basin complex is located along the northeast marginal zone of the Tibetan Plateau. The Yellow River flows through these three basins. For understanding the tectonic and climatic indications of the fluvial erosion of the three basins since Holocene, the authors calculated the erosion quantity by using geological cross sections combined with digital elevation model (DEM). First, the points selected for the interpolation were picked out manually from a series of geological profiles. The minimum Pleistocene surfaces were reconstructed within the basins. This method reduced the error caused by the erosion after the deposition. Second, the erosion quantity and the erosion rates since Holocene were obtained by subtracting the modern elevation from the reconstructed surface. The results show that the erosion rate increased from upstream basin (Tongde basin) to downstream basin (Guide basin). The spatial erosion differences may indicate that the uplift of the margin of the Tibetan Plateau was greater than that of the inner part of the plateau.
1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China; 2. China University of Geosciences (Beijing), Beijing 100083, China
ZhaoShangmin, ChengWeiming, ChaiHuixia, et al. Research on the information extraction method of periglacial geomorphology on the Qinghai-Tibet based on remote sensing and SRTM: A case study of 1: 1, 000, 000 Lhasa map sheet (H46). Geographical Research, 2007, 26(6): 1175-1185. [赵尚民, 程维明, 柴慧霞等. 基于遥感与SRTM的青藏高原冰缘地貌信息提取方法: 以1: 100万标准分幅拉萨幅(H46)为例. 地理研究, 2007, 26(6): 1175-1185. ]
Qinghai-Tibet Plateau located in southwestern China is one of the important geomorphological units of the country's terrestrial part. Because of its high altitude, vast area, and the mid-latitude location, known as "the third pole", it has close correlation with the biggest monsoon system on the globe which has not only sensitive responding character but significant impact on the global climate change. Hence it becomes one of the hot spots of research. Specific geographical environment, unique sea level elevation and frigid climate condition of the Qinghai-Tibet Plateau make kinds of periglacial geomorphology brand into the geomorphological landscape of the Plateau. Taking the district of 1 ∶ 1,000,000 international standard of Lhasa map sheet (serial number H-46) as an example, this paper explores an information extraction method of periglacial geomorphology on the Qinghai-Tibet Plateau based on multiple source data such as remote sensing data, SRTM, air temperature and ground temperature. In the research, the primitive boundary of periglacial geomorphology is acquired by the indexes such as annual mean temperature of national standard station with a resolution of 1km, annual mean ground temperature and elevation through models. The bound is revised and synthetically processed by using the features such as color, shape and texture of remote sensing images (TM and ETM+ of Landsat). Hence the extent of periglacial geomorphology of the study area is determined. Then the morphological indexes such as relief, elevation and slope of the periglacial geomorphology in the study area are computed by using the SRTM-DEM data. Based on the features such as the completeness of geomorphological units, in virtue of geomorphological expert knowledge and the features of remote sensing images, the indexes are revised by using man-computer mutual intelligentized extraction method.At length quantificational exaction of morphological indexes of periglacial geomorphology in the study area is completed. Finally, the morphological characters of periglacial geomorphology in the study area are integrated and the semi-auto matic remote sensing interpretation result map of periglacial geomorphology in the study area and statistical attribute data are achieved. This research can accomplish remote sensing precise location of geomorphological unit boundary and exact attribute evaluation of geomorhpological types based on multiple source data, which promotes the development of extraction methods of remote sensing geomorphological information. Thus the research method can extend to other areas of the Qinghai-Tibet Plateau and is important in theory and practice.
1. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 2. Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China; 3. Taiyuan University of Technology, Taiyuan 030024, China
根据模型和分布函数,本文首先依据多年平均气温、地温和SRTM等数据对研究区域冰缘地貌的分布范围进行分别提取,并利用遥感数据和人工解译方式对其进行了修正。在此基础上,采用一定指标,利用SRTM数据对冰缘地貌次级类型(如起伏度、海拔高度和坡度等)进行了提取,从而完成研究区域冰缘地貌信息的提取。研究结果表明:①研究区域冰缘地貌总面积约5.15×10 4 km 2 ,主要分布在研究区域的西北部和西南部,另外在东北部也有少量分布;通过提取,研究区域中最重要的冰缘地貌类型是冰缘作用的中起伏缓极高山,面积约0.82×10 4 km 2 ,分布范围较广。②冰缘地貌的分布与海拔高度、气温和地温等有密切的关系,基于此提取的结果可为冰缘地貌的解译提供一定的参考;由于青藏高原气象站点较少,数据精度较低,自动提取精度受到很大限制,因此进行人工解译修正是非常重要和必不可少的。
HuangQian, PingJingsong, SuXiaoli, et al. New features of the moon revealed and identified by CLTM-s01. Sci China Ser G, 2009, (10): 1362-1370. [黄倩, 平劲松, 苏晓莉等. 嫦娥一号CLTM-s01模型揭示和证认的月球地形新特征. 中国科学: G辑, 2009, (10): 1362-1370. ]
YuanYuefeng, ZhuPeimin, ZhaoNa, et al. Automatic identification of circular mare craters based on mathematical morphology. Sci China Ser G, 2013, 43: 324-332. [袁悦锋, 朱培民, 赵娜等. 基于数学形态学的月海圆形撞击坑自动识别方法. 中国科学: G辑, 2013, (3): 324-332. ]
Identification of lunar crater is very significant, because the crater is not only the most common geological unit on the surface of the moon, but also an important object to study lunar geological evolution history and the fundamental basis of lunar geological dating. This paper conducts to recognize and extract the craters automatically based on mathematical morphology, from the lunar CCD image acquired by the Chang'e I satellite. The grayscale of the crater rims vary obviously in the CCD image, and their gradient are large, which can be calculated to obtain the shape of crater rim. In general, results of crater rims extracted by edge detection based on sharp grayscale gradient of image are discontinuous and rough, and also have gaps and holes. Some processings are further done to take the smooth and continuous arcs of crater rims, by measuring and extracting the corresponding shape from the image with a certain form of structural elements according to the basic idea of mathematical morphology. And then processed arcs may be used to fit the rims of craters conveniently and to obtain the diameters and locations of craters. The algorithm based on mathematical morphology for crater identification is as follows: firstly, we calculate the gradient of grayscale of the CCD image to form a gradient image, and binarize it; then separate the rims by mathematical morphology; finally extract the sizes and locations of craters by fitting rims with circles. In this paper, experiments on identification of craters in lunar mare and terra area show that the algorithm designed by authors may identify the crater with smallest diameter of 10 pixels. The identification of mare craters is accurate and reliable, while of terra craters is a little worse, due to big grayscale variety in CCD image background caused by big lithological differences and fluctuant topography, so we need a futher study on improvement of algorithm.
1. Institute of Geophysics & Geomatics, China University of Geosciences (Wuhan), Wuhan 430074, China; 2. The Engineering & Technical College of Chengdu University of Technology, Leshan 614000, China
The mathematical statistics and spatial analyses for lunar near side impact craters are used to unravel potential spatial heterogeneity based on the crater nomenclature released by International Astronomical Union (IAU) and topography and imagery data from Chang'E-1(CE-1).The spatial heterogeneity is mainly embodied in the following aspects: (1)the craters with larger diameters dominantly distribute in the highland and show obvious concentration tendency, however, the mare have much fewer larger craters, accompanying by munificent smaller craters; (2) larger craters have the characteristics of randomness and the smaller crater are concentrated in local areas; (3) density differences: the regions closer to equator have higher crater frequencies than the regions to the pole; the trailing hemisphere is cratered at a higher rate than the leading hemisphere; the most densely cratered region is located in the south-central part of the lunar nearside; (4) depth-diameter ratios differences: the craters with depth larger than 2.5 km almost are found in the highland, and there is a marked concentration of points around the central meridian where it cuts through the southern continent; between 57°N and 24°S, the ratio is at a high level; the maximum value occurs near 14°N, and the average value fluctuates at 0.14; approaching the poles, the ratios are becoming smaller, and the minimum value occurs at the south pole region; and (5) gradient differences: the average of crater's maximum gradient in highland is far greater than the value of craters in mare; the average of crater's maximum gradient shows apparent pattern: from lunar equator to the poles, the average of crater maximum gradient increases gradually. The spatial pattern of lunar craters shows marked regional differentiation characteristics, and the relationship between the pattern and the crater forming theory remains much work to be done before the ultimate goal can be reached.
1. State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 2. University of Chinese Academy of Sciences, Beijing 10049, China; 3. The School of Urban and Environmental Science, Northeast Normal University, Changchun 130024, China
ZhouZengpo, ChengWeiming, ZhouChenghu, et al. Characteristic analysis of the lunar surface and automatically extracting of the lunar morphology based on CE-1. Chinese Science Bulletin, 2011, 56(1): 18-26. [周增坡, 程维明, 周成虎等. 基于“嫦娥一号”的月表形貌特征分析与自动提取. 科学通报, 2011, 56(1): 18-26. ]
The satellite Chang’E-1(CE-1) was launched in October 24, 2007 in China, which obtained a large number of scientific data of the global moon, including imageries and laser altimetric data. In this paper, the characteristics of the lunar surface are analyzed and the lunar morphologic information of the lunar mare and highland is automatically extracted based on the imagery acquired by CCD camera and the DEM processed by three-line digital photogrammetric technology. The results show that the average elevation of the global moon is -742 m; the highest and lowest locations stand in the farside of the moon; the highest is at the eastern margin of Engel’gardt crater; the lowest is in the secondary impact crater pit of Minkowski crater. The surface of the moon is very flat; most of its slope is bellow 15°, accounting for 90% of the total area of the global moon. The great variation of slope value mainly distributes in the lunar highlands, with an average slope of greater than 7°. The lunar mares widely distribute in the nearside of moon, with an average slope of below 3°. The optimum statistical unit for lunar relief value is 16 km 2 . The mare and highland are the basic types of lunar morphology, which can be automatically extracted by maximum likelihood classifier based on the elevation data and slope, relief and imagery data. The values of altitude, slope, relief and grey level of CE-1 imageries are normalized and binarized. A case study of H010 (locating in 0°-18°W, 0°-14°S) shows that the overall accuracy assessment for extracted results of the lunar mare and highland based on the geological data published by USGS in 1971 is better, and the Kappa coefficient is 0.78, and the results of the lunar mare and highland show that the method can be used to extract the characteristics of lunar surface.
1. State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographic and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; 2. Graduate University of Chinese Academy of Sciences, Beijing 10049, China; 3. School of Urban and Environmental Sciences, Northeast Normal University, Changchun 130024, China
考虑流域下垫面空间变异性,基于数字高程模型构建了数字流域,并在此基础上对描述流域水文物理过程的数字方法进行了探讨.文章认为,数字水文模型是一种有物理基础的包含大容量信息的现代模拟技术.史灌河流域实例研究表明,数字水文模型可以十分方便地输出水文要素和状态变量的空间分布与时间序列,这对充分利用现有观测信息进行水文信息的深层挖掘创造了条件. Abstract: Digital basinis made from digital elevation model considering spatial variability within a catchment.On the basis of digital basin,the digital approach to describing hydrological processes within a catchment is investigated.Digital hydrological model is regarded as a modern physically-based modeling technique that includes a large amount of information.The case study on the Shiguanhe catchment in the Huaihe River Basin,intensified observation field of GEWEX Asian Monsoon Experiment Project,has shown that the digital mode lperforms very well not only in simulating runoff processes at any specific site,but also in simulating spatial distribution and temporal variation of hydrological elements and state variable(especially soil moisture),if compared with traditional hydrological models.That provides solid foundation for full use of now available observation in formation and in-depth mining of hydrological data.
XieShunping, DuJinkang, WangLachun. Methods for processing depression and flat areas in extracting drainage networks based on the DEM. Advances in Water Science, 2005, 16(4): 535-540. [谢顺平, 都金康, 王腊春. 利用 DEM 提取流域水系时洼地与平地的处理方法. 水科学进展, 2005, 16(4): 535-540. ]
How to process depression and flat areas and their drainage direction is a key issue and must be solved prior to the extraction of drainage network based on the digital elevation model(DEM).This paper investigates the shortcomings of the existing methods for the complex terrain DEM with depressions and flat areas,and proposes several new methods,namely,the classification and the merger of depressions,the valid filing depression,the classification of flat areas,and the construction of the drainage direction based on the flow cost for the river valley plains.These methods can be performed in the software system developed by authors. The test shows that the methods mentioned above can be used to process complex depressions validly and construct flat areas water flow direction in the consideration of the ambient terrain and astringency to the potential waterway. And they are proved to be rationa. In addition,by using the methods,odd waterways such as parallel and pseudo ones can't be generated in the extraction of the drainage network. Hence the results obtained are consistent with the real situation.
Department of Urban and Resources Sciences, Nanjing University, Nanjing 210093, China
XuJingwen, ZhangWanchang. A new method for treating the depressions and flat areas in DEM for large-scale hydrology and climate models. Journal of Hydraulic Engineering, 2007, 38(12): 1414-1420. [徐精文, 张万昌. 适用于大尺度水文气候模式的 DEM 洼地填充和平坦区处理的新方法. 水利学报, 2007, 38(12): 1414-1420. ]
Xiong LY, Tang GA, YanS. , et al. Land form-oriented flow-routing algorithm for the dual-structure loess terrain based on digital elevation models. Hydrol Process, 2014, 28(4): 1756-1766.
1 Nanjing Normal University, Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing, China 2 Department of Earth Sciences, University of Hong Kong, Hong Kong, SAR, China
ZhuHongchun, TangGuoan, WuLiangchao, et al. Extraction and analysis of gully nodes based on geomorphological structures and catchment characteristics. Advances in Water Science, 2012, 23(1): 7-13. [朱红春, 汤国安, 吴良超等. 基于地貌结构与汇水特征的沟谷节点提取与分析. 水科学进展, 2012, 23(1): 7-13. ]
A gully node is the intersection of gully or river networks, which reflects the geomorphological structure and hydrological characteristic of the gully area. Effective extraction and analysis of gully nodes are essential to understand the spatial structure, morphology, and hydrological characteristic of a catchment. An algorithm based on high resolution digital elevation model (DEM) data is proposed for extracting gully nodes together with the classification method. The algorithm and method are tested in an experimental area on the Loess Plateau of North Shaanxi Province. The numbers of gully nodes of different order gullies and the flow accumulation value associated with each gully node are obtained. The relationship between the numbers of gully nodes in any given order class and the sum of corresponding flow accumulation values is obtained using a mathematical model. The variations in the spatial distribution of flow accumulation values in different geomorphological regions are studied using the arithmetic progression classification method. Finally, the spatial regularity of geomorphological features is preliminary discussed.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing 210046, China; 2. Geomatics College, Shandong University of Science and Technology, Qingdao 266590, China; 3. Aerial Photogrammetry and Remote Sensing Bureau, Xi'an 710054, China
WangZhonggen, LiuChangming, ZuoQiting, et al. Methods of constructing distributed hydrological model based on DEM. Progress in Geography, 2002, 21(5): 430-439. [王中根, 刘昌明, 左其亭等. 基于 DEM 的分布式水文模型构建方法. 地理科学进展, 2002, 21(5): 430-439. ]
Resent advances in remote sensing, geographic information systems, and computer technology make the use of distributed hydrological model, based on digital elevation model (DEM), an attractive approach or tool to studying hydrological processes and evolution laws of water resources under changing environment. But distributed hydrological model is not perfect compared with lumped hydrological model. In order to promote its development, based on DEM, this paper discusses and sums up the characteristics of distributed hydrological model, then probes into two main ways and means of constructing distributed hydrological model. One way is like SHE model, another is like SWAT model. Although distributed hydrological models can be made in different ways, the primary structure of the model is quite similar. A typical structure of DEM based distributed hydrological model is provided in this paper. To better study the impact of the changing environment on hydrological processes, a watershed must be divided into subunits. This paper expressly discusses the three most common techniques used to discretize a watershed, which are respectively grid cell discretization, representative hillslope discretization and subwatershed discretization. In the final, as to the problem of constructing model, the methods of building the components of the distributed hydrological model is set forth from three aspects: input module, unit hydrology model and river routing model. A brief comment on the current distributed hydrological model research and some advice are given in the conclusion. All these will provide a guidance for making distributed hydrological model based on DEM.
1. Institute of Geographical Sciences and Natural Resources Research,CAS, Beijing 100101 China; 2. College of Hydraulic & Environmental Engineering, Zhengzhou University, Zhengzhou 450002 China; 3. Hydraulic and Electric Engineering Department of Wuhan University,Wuhan 430072 China
Gaochao, JinGaojie. Effect of DEM resolution of results of the SWIM hydrological model in the Changtaiguan Basin. Geographical Research, 2012, 31(3): 399-408. [高超, 金高洁. SWIM 水文模型的 DEM 尺度效应. 地理研究, 2012, 31(3): 399-408. ]
In this paper,the impacts of the Digital Elevation Model(DEM) with different resolutions on the simulation results of the SWIM hydrological model are examined for the Changtaiguan basin in the upper reaches of the Huaihe River basin in East China.Fifteen DEM resolutions(from resolution of 1000x1000 m to resolution of 30x30 m) are analyzed on their impacts on landscape parameters and runoff simulation results.Based on this,it is found that the best fitting DEM resolution in the study area is 90~120 m,and that both the ratio of Grid Area/Basin Area and the 'thousand million' formula are suitable methods.The Nash-Sutcliffe coefficients decline with DEM resolution;yet when DEM resolution is larger than 250 m,the Nash-Sutcliffe coefficients increase,because DEM grid is too coarse to display basin terrains.The simulation results of hydrological extreme events from 15 different DEM resolutions show a high variability.The high Nash-Sutcliffe coefficients do not reflect the hydrological extreme events,especially in the flood period.For the dry season,the simulation results of the 15 DEM resolutions show relatively good results.The results of the SWIM hydrological model are more sensitive to precipitation when the DEM resolution is decreasing.
1. College of Territorial Resources and Tourism, Anhui Normal University, Wuhu 241000, Anhui, China; 2. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, CAS, Nanjing 210008, China; 3. Library of Anhui Normal University, Wuhu 241000, Anhui, China
Li ZL, Xu ZX, ShaoQ, et al. Parameter estimation and uncertainty analysis of SWAT model in upper reaches of the Heihe river basin. Hydrol Process, 2009, 23(19): 2744-2753.
1 College of Water Sciences, Beijing Normal University, Beijing 100875, China 2 CSIRO Mathematical and Information Sciences, Private Bag 5, Wembley, WA 6913, Australia 3 Department of Geography, University of Guelph, Guelph, N1G2W5, Canada * College of Water Sciences, Beijing Normal University, Xinjiekouwai Street 19, Beijing 100875, China.
Li ZL, Xu ZX, Li ZJ. Performance of WASMOD and SWAT on hydrological simulation in Yingluoxia watershed in northwest of China. Hydrol Process, 2011, 25(13): 2001-2008.
1 School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China 2 Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Water Sciences, Beijing Normal University, Beijing 100875, China * School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China.
The Digital Elevation Drainage Network Model (DEDNM) of the Shiguanhe River catchment is made from digital elevation model by Martz and Garbrecht method with spatial basin heterogeneity considered. Subwatershed, drainage network, and their spatial topological relations are generated automatically by computer. Then, spatial cumulative distribution probability of topographical index ln (a/tgβ) i in the TOPMODEL is calculated. Therefore the parabolic exponent of soil tension water storage capacity distribution within each subwatershed in the Xin'anjiang model can be obtained by dimensionless processing with respect to cumulative distribution curve of ln(a/tgβ) i . That makes the parabolic exponent in the Xin'anjiang model be physically based. Finally, the digital hydrological model is established. The case study on the Shiguanhe River catchment in the Huaihe River Basin, i.e., the intensified observation field of GEWEX Asian Monsoon Experiment Project, showed that the digital model performs very well not only in simulating runoff processes at any specific outlet, but also in simulating spatial distribution and temporal variation of hydrological elements and state variables (especially soil moisture), if compared with traditional hydrological models. That provides solid foundation for making full use of present observation information and thorough tapping potentials of hydrological data.
College of Water Resources and Environment, Hehai University, Nanjing 210098, China
基于数字高程模型,考虑流域空间的变异性,建立数字高程流域水系模型。产流子单元的划分、河网水系的生成及其空间拓扑关系的建立,是由计算机自动完成。计算TOPMODEL地形指数ln(a/tgβ) i 的空间累积分布曲线,并对其作无量纲化处理,推求各产流子单元的土壤蓄水容量分布抛物线参数B,构建数字水文模型。全球能量与水循环亚洲季风试验强化观测区—淮河史灌河流域实例研究表明:数字模型不仅可以很好地模拟流域出口断面的径流过程,而且能够模拟土壤水分的变化过程,还可十分方便地输出水文要素和状态变量的空间分布。这对充分利用现有观测信息进行水文数据的深层次挖掘奠定了基础。
LiuChangming, LiDaofeng, TianYing, et al. An application study of DEM based distributed hydrological model on macroscale watershed. Process in Geography, 2003, 22(5): 437-445. [刘昌明, 李道峰, 田英等. 基于DEM的分布式水文模型在大尺度流域应用研究. 地理科学进展, 2003, 22(5): 437-445. ]
The paper selected the macro-scale areas of the source region of the Yellow River as an object and carried out discharge simulation with the distributed hydrological model,the SWAT model.Based on the analysis and process of DEM data,such as flow direction,a watershed borderline,a river network and sub-basins by automatically becoming,rivers,codes and areas of sub-basins,structure and topology constraint of the river network were gained with a format of grid cells.Annually and monthly measured runoff data of Tangnaihai hydrologic station from 1976~1985 were used to calibrate the simulation parameters and determine some basic parameters of the model.The simulation results are satisfactory and show that climate change is the main reason for discharge change of the source regions of the Yellow River.In twenty years of the 1980’s and the 1990’s,the discharge decrease due to climate change is 62.11×108m 3/s,which accounts for 108.72% of total discharge change,and the discharge increase due to land-cover change is 5.73×108m 3/s ,which accounts for 10.03% of that with grid cell.
1. State Key Joint Laboratory of Environmental Simulation and Pollution Control,Key Laboratory for Water and Sediment Sciences of Ministry of Education,Institute of Environmental Sciences,Beijing Normal University,Beijing 100875; 2. Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China; 3. Department of Civil Engineering,The University of Hong Kong,Hong Kong
ZhuAxing, PeiTao, QiaoJianping, et al. A land slide susceptibility mapping approach using expert knowledge and fuzzy logic under GIS. Progress in Geography, 2006, 25(4): 1-12. [朱阿兴, 裴韬, 乔建平等. 基于专家知识的滑坡危险性模糊评估方法. 地理科学进展, 2006, 25(4): 1-12. ]
Current methods cannot meet the needs of evaluating landslide susceptibility because they cannot incorporate the nonlinear relations between landslide and the inducing factors as well as the different forms of relationships. A new approach integrating the expert knowledge and fuzzy logic is proposed in this paper to evaluate the landslide susceptibility. This method first encodes the knowledge from domain experts into four combinations of environmental factors: 1) the difference between slope gradient and the strata gradient as well as the difference between slope orientation and strata orientation, 2) slope gradient and lithology, 3) slope height and lithology, and 4) slope shape and lithology, and thus incorporates the relativity between factors into these combination models. Information on variables involved in these combinations is characterized using a set of GIS techniques. The susceptibility of a given location hence can be evaluated by evaluating each combination and overlaying the values from these four combinations. Some parameters in these models are determined by statistical analysis, and others are provided by landslide experts. The approach is applied to a section of the Three Gorges area from Yunyang to Wushan, and a susceptibility map is produced. The result shows that the computed susceptibility values are much higher over areas with landslides than areas without landslides. We conclude that our approach is capable of capturing the landslide susceptibility.
1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China| 2. Department of Geography, University of Wisconsin Madison, 550N, Park Street, Madison 53706, USA| 3. Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, China
ZhangCaixia, YangQinke, LiRui. Advancement in topographic wetness index and its application. Progress in Geography, 2005, 24(6): 116-123. [张彩霞, 杨勤科, 李锐. 基于 DEM 的地形湿度指数及其应用研究进展. 地理科学进展, 2005, 24(6): 116-123. ]
Topographic wetness index, which takes into account the integrated effects of topography and soil hydraulic characters on soil moisture, plays important theoretical and applied potentials in the studies of spatial distribution of soil moisture. Considering the spatial-temporal variation in upslope contributing area, topographic wetness indexes were divided into three types, e.g. static, quasi-dynamic and full dynamic. The effects of computing methods of topographic wetness index and resolution of DEMs as well as the universality of the index should be analyzed discreetly in application of topographic wetness index. At the same time, for the apparent differences between the current assumptions of topographic wetness index and actual water cycling process and runoff mechanism in arid/semi-arid region, the research approaches and the conceive of the application of topographic wetness index are proposed for the Losses Plateau to provide theoretical and practical foundation for the vegetation restoration and the conservation of soil and water in the region.
1. College of Resource and Environment, Northwestern Sci-tech University of Agriculture and Forestry, Yangling 712100, China| 2. Institute of Soil and Water Conservation, CAS and Ministry of Water Resources, Yangling 712100, China
QinChengzhi, YangLin, ZhuAxing, et al. Computation method of topographic wetness index in low relief area. Progress in Geography, 2006, 25(6): 87-93. [秦承志, 杨琳, 朱阿兴等. 平缓地区地形湿度指数的计算方法. 地理科学进展, 2006, 25(6): 87-93. ]
Topographic wetness index, which is designed for modeling the status ( “dry”or “wet”) of the soil moisture quantitatively, is an important index for both predictive soil mapping and distributed hydrological modeling in a catchment. Current methods for calculating topographic wetness index have evident problems when applied in low relief area. Outside the positions of narrow accumulation line with high topographic wetness index, the topographic wetness index dramatically jumps down in other parts of wide valley area. This is unreasonable because the soil moisture should be comparatively average and high in the wide and flat valley, and the value of topographic wetness index should be high. This problem is caused by both the flow accumulation algorithm and the slope gradient used during computing the topographic wetness index. A new method for computing topographic wetness index is proposed in this paper to address this problem. Firstly, flow accumulation is calculated by a multiple flow direction algorithm (MFD- fg). Topographic wetness index is then computed by the flow accumulation and maximum downslope. The maximum downslope used in the computation of topographic wetness index is matched with the idea of both MFD- fg and topographic wetness index. Furthermore, a post - processing method is also proposed to compute the topographic wetness index in valley area. The topographic wetness index in the valley area is interpolated by a Gaussian function based on the value of the topographic wetness index on the nearest position on extracted flow accumulation line. The application in a small watershed shows that the method proposed in this paper can get a comparatively reasonable distribution of topographic wetness index for not only the hillslope but also the wide valley area. The value of topographic wetness index in valley area is averagely high and with a smooth transition, which reflects the natural status of the soil moisture in application area. In the future research, the method proposed in this paper will be evaluated by both artificial surfaces and the real applications.
1. State Key Laboratory of Resources and Environmental Information System, Institute of Geographical Sciences and Natural Resources Research, CAS, Beijing 100101, China| 2. Department of Geography, University of Wisconsin-Madison, Madison, WI 53706, USA
Abstract: Terrain is one of the main environmental factors that influence ground water and soil erosion. Slope gradient, Slope length, and LS factor are important in soil erosion models. In this paper, DEM with a resolution of 25m was built in the software ANUDEM and slope, slope length, and LS factor were calculated with support from the fourth national soil erosion survey. Spatial and statistical characteristics for terrain factors that influence soil erosion were analyzed, and the result was contrasted with two kinds of remote sensing based elevation data that were used widely. The result showed that the typical terrain characters could be expressed by Hc-DEM with a resolution of 25m. Slope gradient and a slope length based on 25m Hc-DEM in accordance with the conventional understanding. Slope gradient was gentlest in the northeast region and steepest in the Loess Hilly region. Slope length was longest in the northeast region and shortest in the Loess Hilly region. Slope gradient was gentle in the bottom of valleys and ridge areas with higher elevation, and was steep in areas between the ridge and deposition areas. In areas with great relief steep hilly areas or gentle hilly areas, slope length was longer. The spatial distributions of LS factor were similar with that of the slope gradient. The data of this research was proven to be better than ASTER and SRTM elevation data. Moreover, the DEM data built in the fourth national soil erosion survey was irreplaceable in the field of soil erosion mapping at the national, province, and large watershed scales. This paper showed the characteristics of erosional terrain in the main water erosion region in China, and the result provided a basis for the calculation of terrain factors in research of soil erosion and hydrology.
地形是影响地表水文和土壤侵蚀的主要环境因素,坡度、坡长和LS因子是土壤侵蚀模型的重要参数。该文以第四次全国土壤侵蚀普查项目为依托,在ANUDEM软件环境中建立25m分辨率文地貌关系正确的DEM(Hydrologically Correct Digital Elevation Model, Hc-DEM),提取了坡度、坡长并计算了LS因子,对中国主要水蚀地区的土壤侵蚀地形因子的空间及统计特征进行了分析,并将该数据与目前应用较为广泛的2种遥感高程数据进行了对比。结果表明,25m分辨率Hc-DEM可用以表达各典型样区地形特征,其上提取的坡度和坡长,符合一般地貌学原理和常规认识;坡度在东北地区最为平缓(0.8°),而在黄土丘陵区最陡(22.3°);坡长则在东北地区最长而黄土丘陵区最短(479m和69m);在地势比较低的河谷和地势较高的分水地带坡度比较平缓,而在分水岭到河谷冲积平原之间坡度较陡;在地形起伏较大的陡坡丘陵或坡度平缓的丘陵,坡长均比较大;LS因子的空间分布格局与坡度基本一致;该文得到的数据与ASTER和SRTM遥感高程数据对比具有明显优势,全国土壤侵蚀普查项目建立的DEM,在全国、省区和大流域尺度上的土壤侵蚀评价制图中具有不可替代性。该文阐明了中国主要水蚀区的侵蚀地形特征,为土壤侵蚀学、水文学中地形因子的提取提供了参考。
HaoChengyuan, XuChuanyang, WuShaohong. Total solar radiation spatialization in mountainous region based on DEM and climatological calculation. Resources Science, 2009, 31(6): 1031-1039. [郝成元, 许传阳, 吴绍洪. 基于DEM模型和气候学计算的滇南山区太阳总辐射空间化. 资源科学, 2009, 31(6): 1031-1039. ]
Different temperature, precipitation and solar radiation, resulted from different regional landform and elevation, are the main factors of regional differences. Total solar radiation is the major energy source of earth surface processes, including physical, chemical and biological processes, and also a basic parameter to understand or explain the changes of land surface patterns. In this research, we build a multi-year average model for annual total solar radiation spatialization from 1961 to 2000 by using two main climatological calculation models, Angstrom model and Bristow-Campbell model, at the same time. It has been realized through two processes, including both the spatialization of potential solar radiation and the climatological calculations of solar radiation between different models, and has successfully resolved the spatialization of monthly total solar radiation databases with an area of 250m ×250m in southern Yunnan Province, regarding DEM, monthly differences of minimum and maximum temperatures, latitude, declination, and monthly average sunshine percentage as the basic data. More importantly, we find the simulation result quite good by contrasting land-ground measurement data and simulated grid data. Solar radiation error rates of each month are 3.69% on average, far below 10%. Meanwhile, this applicable spatialization mode of total solar radiation in southwest of China can be used in other regions for reference, especially in mountainous areas. In the application of this model, two aspects can influence error ratio. The first one is how to decide the parameter value of surface vegetation reflectance in different months because there is an obvious seasonal change of vegetation cover throughout a year. It may be the main source of error in this model and is one of the key problems to be resolved in the next step of our research. The second one is how to improve the DEM spatial resolution. The error ratios may be much lower if the spatial resolution of 250m × 250m in this study can be improve to 100m × 100m or 25m × 25m since the largest surface characteristics of the mountainous region is the complicated terrain.
WuXianfeng, WangZhonggen, LiuChangming, et al. Digital rainfall-runoff model based on DEM: The application to Xiaolangdi-Huayuankou section of the Yellow River Basin. Acta Geographica Sinica, 2002, 57(6): 671-678. [吴险峰, 王中根, 刘昌明等. 基于DEM的数字降水径流模型在: 黄河小花间的应用. 地理学报, 2002, 57(6): 671-678. ]
DEM is the main data source which is used in watershed analysis. There are many mature algorithms in watershed analysis and they can be used to delineate the drainage networks. Applications of the methods based on DEM make significant innovation in hydrological simulations. Topographic parameters which are used in hydrological models can be automatically calculated from DEM. The article introduces the main process to determine watershed geometry, drainage network and other map-type information for hydrological models. Lushi basin, located in the upper Luohe river which is a tributary of the middle Yellow River, was selected as the study region with an area of 4,623 km2. WMS6.1, a GIS hydrological tool, which is introduced to China recently, was used to develop the digital rainfall-runoff model, and other GIS tools such as ARC/Info, Arcview were also used to deal with the data. The drainage network was derived from 1:250,000 DEM, and the region was divided into seven sub-basins. HEC-1 model, a part of hydrological models in WMS, was selected to simulate the rainfall-runoff process. Curve Numbers (CNs) and other parameters were automatically calculated to input to models directly. Five historical flood events were simulated. The results demonstrate that the method was more efficient than trade method. Although it is very easy and quick to input and output data for the models, it does not mean that the hydrological model itself has high quality, so it is necessary to develop hydrological models which can be adapted to the region.
1. Institute of Environmental Science, Beijing Normal University, Beijing 100875, China; 2. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 3. The Bureau of Hydrology, YRCC, Zhengzhou 450003, China
LiuSanchao, ZhangWanchang, GaoMaofang, et al. Simulation of land surface evapotraspiration using distributed hydrological model, remote sensing and GIS technology. Scientia Geographica Sinica, 2007, 27(3): 354-358. [刘三超, 张万昌, 高懋芳等. 分布式水文模型结合遥感研究地表蒸散发. 地理科学, 2007, 27(3): 354-358. ]
Evapotranspiration(ET) is the key factor to the research on water circulation and heat balance in the soil-vegetation-atmosphere system.In this article,a pixel based adapted DHSVM distributed hydrological model that integrates remote sensing and geographic information system was applied in the Ziwuhe River watershed in the upper Hanjiang River basin.The modeled pixel is 60 m large.Our study focused on the atmospheric and topographic correction on optical remote sensing data and utilizing 30 m resolution Landsat TM data to obtain leaf area index and the land use and land cover data.Some useful terrain factors as slope and aspect and topographic index could also be derived from digital elevation model.The results showed that the spatial pattern of ET was similarity in different temporal scales,moreover,it was found that daily ET spatial differences were more evident.The result also showed that the distributed model could be used in small basin of humid climate.
1. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sicences, Beijing 100101; 2. International Institute for Earth System Science, Nanjing University, Nanjing, Jiangsu 210093
PanYaozhong, GongDaoyi, DengLei, et al. Smart distance searching-based and DEM-informed interpolation of surface air temperature in China, Acta Geographica Sinica, 2004, 59(3): 366-374. [潘耀忠, 龚道溢, 邓磊等. 基于DEM的中国陆地多年平均温度插值方法. 地理学报, 2004, 59(3): 366-374. ]
Statistical interpolation of the temperature for the missing points is one of the most popular approaches for generating high spatial resolution data sets. However, many interpolation methods used by previous studies are purely mathematic ways, without geographical significance being considered. In the present study the authors interpolate the monthly and annual mean temperature climatologies using 726-station observations in China, utilizing improved methods by taking into account geographical factors such as latitude, longitude, altitude. In addition, a smart distance-searching technique is adopted, which helps select the optimum stations on which the guess values at missing points are generated. Results show that the methods used here have evident advantages over the previous approaches. The mean absolute err of ordinary inverse-distance-squared (IDS) technique is in the range of 1.44-1.63 o C, on average 1.51 o C. The smart distance searching technique yield a MAE of 0.53-0.92 o C, on average 0.69 o C. Errors have been reduced as much as 50%.
Geoinformatics Center, Institute of Resources Science, Beijing Normal University, Beijing 100875, China
以1961~2000年全国726个气象站点旬平均温度为基础数据,在分析了多年月平均温度和年平均温度的空间分布与经度、纬度、高度的内在关系后,提出了一种基于DEM和智能搜索距离的温度空间插值方法 (SSI),并与反距离平方 (IDS) 等传统方法进行了对比。交叉验证结果表明:1) 传统的IDS方法最优结果的MAE范围是1.44 o C~1.63 o C,平均1.51 o C;而SSI温度插值方法的平均绝对误差为0.53 o C~0.92 o C,平均值0.69 o C,精度超过IDS等方法一倍以上。2) 随着距离的增大,站点间温度的相关性逐渐降低,会降低估算精度;小于一定的搜索半径,被估算点周围的相邻站点的数目逐渐减少,同样会降低插值的精度,因而对中国陆地部分温度插值而言,最优的空间插值搜索半径介于150~250 km之间。最后,结合DEM数据,生成了0.1 o × 0.1 o 中国陆地区域多年月平均和年平均温度栅格图像数据集,该结果表明:利用SSI方法不仅可以生成高精度、高空间分辨率的网格温度结果,而且其插值结果能客观细致的反映温度随经度、纬度和高度梯度变化的地带性特征。
YangX, Tang GA, Xiao CC, et al. Terrain revised model for air temperature in mountainous area based on DEMs. Journal of Geographical Sciences, 2007, 17(4): 399-408.
In mountainous area, spatial interpolation is the traditional method to calculate air temperature by use of observed temperature data. Due to lack of sufficient observation data in mountainous areas many precise interpolation methods could give only coarse result which could not meet the demand of precision agriculture and local climate exploration. Based on DEMs of 25 m resolution, a reversed model is constructed, with which temperature is simu-lated to the corresponding slope unit from the solar radiation. Taking Yaoxian county as a test area, and mean monthly temperature data as basic information sources, which are collected from 15 weather stations around Yaoxian county in Shaanxi province from the year of 1970 to 2000, a simulation for the solar radiation cell by cell is completed. By simulating solar radia-tion at each slope and flat cell unit, the terrain revised temperature model could be realized. A comparison between the simulated temperature and the radiation temperature from TM6 thermal infrared image shows that the terrain improved model gets a finer temperature dis-tribution at local level. The accuracy of simulated temperature in mountainous area is higher than it is in flat area.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing 210046, China| 2. Shaanxi Remote Sensing Information Center for Agriculture, Xi’an 710015, China
LongEn, ChengWeiming, ZhouChenghu, et al. Extraction of land form information in Changbai Mountains based on Srtm-DEM and TM data. Journal of Mountain Science, 2007, 25(5): 557-565. [龙恩, 程维明, 周成虎等. 基于Srtm-DEM与遥感的长白山基本地貌类型提取方法. 山地学报, 2007, 25(5): 557-565. ]
WangYiting, ChenXiuwan. Monitoring glacier volume change based on multi-source DEM and multi-temporal remote sensing images. Journal of Glaciology and Geocryology, 2010, 32(1): 126-132. [王祎婷, 陈秀万. 多源DEM和多时相遥感影像监测冰川体积变化: 以青藏高原那木纳尼峰地区为例. 冰川冻土, 2010, 32(1): 126-132. ]
冰川储量变化对全球水循环、能量平衡和区域水资源都具有重要意义,构成全球变化研究的重要方面. 针对当前冰川变化监测技术与方法,提出一种结合多源DEM数据和多时相遥感影像监测冰川体积变化的方法. 以青藏高原那木纳尼峰地区冰川为例,通过MSS/TM遥感数据识别冰川范围,以地形图DEM和SRTM-DEM计算出两时期冰川厚度变化信息,从而计算冰川体积变化值. 计算过程中,对冰川范围识别、遥感数据不同时相、不同源DEM数据的误差进行了分析和控制. 结果显示,1976-2001年的25a间该地区冰川体积减少了3.060 km 3 ,存在着较为强烈的消耗,冰川年损耗速率为0.1224 km 3 8226; a -1 .
ZhangZuo, LiJiangfeng, ChenShuang, et al. Spatial distribution of affordable houses in cities: A case study of Wuhan based on DEM. Acta Geographica Sinica, 2011, 66(10): 1309-1320. [张祚, 李江风, 陈双等. 经济适用住房在城市中的空间分布: 基于DEM的武汉市实例分析. 地理学报, 2011, 66(10): 1309-1320. ]
Affordable housing is associated with social welfare. The spatial location of affordable houses will determine the location of low- and medium-income households in cities, and thus urban social and economic development. The spatial location of affordable houses is concerned with site selection and social equity. A new concept - spatial welfare, and its method of calculation, are proposed. This paper uses Wuhan in Central China as an empirical case study. Spatial locations of affordable houses in this city are investigated by using GIS, DEM (Digital Elevation Model) and the concept of spatial welfare. A discussion of their site selection and spatial quality allocation in a microscopic view is presented in the end.
1. School of Business, Hubei University, Wuhan 430062, China; 2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China; 3. School of Resources and Environment Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
Language plays an important role in communication, sharing and conveying information for human beings. GIS language is very important in understanding, researching, representing and transmitting geographical information. It gradually evolves and develops with promotion of the science and technology progress and cognition level. Concerning with the theoretical progresses from the geographical information ontology, espistemology and linguistic theory, this paper firstly proposes the conception and basic features of GIS language according to the geographical language's changes in language structure, function and characteristics. GIS language could be regarded as a synthetic and digital symbolic system. It is a comprehensive representation of geographical objects, phenomenon and their spatial distribution and dynamic processes. This representation helps us to generate a universal perception of geography space by the geographical scenarios or symbols with geometry, status, processes, temporal-spatial relationship, semantic and attribution features. Furthermore, this paper states that GIS language is a new generation geographical language by its intrinsic characteristics, structure, functions and systematic content. As the former's theoretical foundation, the paper definitely illustrates the important status and contributions of the GIS language to geographical researches. All in all, GIS language is the new geographical language with some new features including temporal-spatial multi-dimension representation, interactive visualization, virtual geographical scenario, multi-sensor sensing, expediently broadcasting with web, in current new era. GIS language is the highest level of geographical language because it integrates the semantic definition, features extraction, geographical dynamic representation and temporal-spatial unifying computation of geographical objects. GIS language have five important characteristics: abstraction, systemization, strictness, definition and hierarchical structure. In summary, GIS language provides a new tool for the recognition, understanding and simulation of the whole geographical environments. So, the exploration of GIS language's function in contemporary geographical development becomes increasingly important. Meanwhile, the construction of the conceptual model and scientific systems of GIS language will promote the development of geography discipline and geographical information sciences. Therefore, the paper forecasts the GIS language's future development from the viewpoints of digital technologies, geography norm, geography discipline development and geographical modeling.
1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing 210046, China; 2. Department of Resources & Environment and Tourism Management, Hengyang 421008, Hunan, China