基于DEM的准噶尔盆地及其西北山区地势起伏度研究

Relief Amplitude in Junggar Basin and peripheral Northwest Mountains

DEM(digital elevation model)数字高程模型,是地貌解译有力的辅助工具,同时也是对地形地貌分析研究进行量化表达的一个重要手段。在对比前人研究方法的基础上通过研究区1：25万的DEM数据和1990年的TM影像,用GIS(地理信息系统)方法和统计方法进行了地势起伏度研究,选取了代表新疆基本地貌特征戈壁、沙漠、丘陵、高山的克拉玛依幅含阿勒泰幅影像进行了试验。将网格单元从3×3、4×4、……一直扩大到60×60,对比不同网格单元内起伏度值的变化情况。最后得出了利用1：25万DEM来计算新疆克拉玛依地区地势起伏度时,20×20的网格大小(4 km^2)可作为曲线变化的拐点,即为曲线由陡变缓的阈值。从而得出了20×20的网格大小(4 km^2)为准噶尔盆地及其西北山区地势起伏度计算的最佳统计单元。

DEM （digital elevation model） is a powerful tool for landform interpretation, and also an important method to express geomorphology quantitively. With DEM and TM（1990） data of the study area, and using GIS measure plus statistical method based upon comparing several different measures of previous researcher＇s works, this paper made a series of experiments on the remote sensing satellite images of the target area by changing grid units from 3 × 3, 4 × 4, .... to 60 × 60 to observe the correspondingly variation of the relief amplitude, and made a fitting curve. The results showed that the curve appeared the inflection point at the grid unit of 20 × 20 （4 km^2）, which may be called ＂threshold＂. Before the inflection point, the curve rose very rapidly, but it grew comparatively much slower after the inflection point; finally it was concluded that the grid unit of 20 × 20 （4 km^2）is the optimum statistical unit for calculating the relief amplitude in Junggar Basin and the peripheral Northwest Mountains, while DEM data at a scale of 1：250 000. Based upon this conclusion, a Relief Amplitude grade map of the study area has been worked out.