DEM网格尺寸对地形因子影响研究——以北京市延庆县八达岭小流域为例

DEM包含了大量地形信息是地形分析的基本资料。众所周知DEM网格愈小,愈能反映地貌起伏变化的细节,对地形的描述愈准确,但是随着DEM精度的增加,数据量将以几何级数递增,所需要的时间、人力以及占用的计算机容量都大大增加,从某种意义上来说,是对计算机资源的浪费。因此DEM网格尺寸对地形因子精度的影响以及选择适宜的网格尺寸在实际应用中就至关重要了。以北京市延庆县八达岭小流域为例,不考虑DEM采样点上高程误差,采用1∶10 000大比例尺,运用统计分析方法,比较当DEM网格尺寸变化时,对坡度,坡向,剖面曲率和平面曲率计算结果的误差,分析网格尺寸的变化与坡度,坡向,剖面曲率和平面曲率计算结果之间定性定量关系。从精度和栅格数据量两个方面选择适宜网格尺寸范围为5~10 cm。此研究对实际应用中DEM网格尺寸选择有一定指导意义。

Studies of the Influences from the Size of DEM Grids on Topographical Factors——Take the Badaling Watershed of Yanqing Beijing as an Example

DEM includes a large amount of topographical information,which made it the basic materials for topography analyzing.It is known to all that the smaller the size of grids,the more indicate it reflects the variety of terrain and the more accurate it describes the topography.However,with the increase of DEM precision,the data volume would increase simultaneous at a speed of geometric progression,meanwhile,the time spending,manpower and capacity of computer would also goes up greatly.In a sense,it is a waste of computer resource.Therefore,the influences from DEM girds size on the precision of topographical factors and choosing suitable grids size are of great importance in practical application.This experiment takes Badaling watershed in Yanqing Beijing as an example,based on 1:10 000 the large geographical scale,adopting statistical analytical methods,the authors compared the errors of the slope,aspect,average cross section curvatures and average surface coarsens curvatures while the DEM grids varies.Besides,the authors analyzed the qualitative relation between variety of grids size and the slope,aspect,average cross section curvatures and average surface coarsens curvatures with the results of calculation.Taking accuracy and data volume into account,a suitable grids size:5~ 10 cm was chosen.It has directive significance to the choosing of DEM grids size in practical application.