Comparison of the extracted DEMs in Heihe River upper and middle reaches

The Digital Elevation Model (DEM) are terrain elevations at regularly spaced horizontal intervals, i.e., an a grid of regularly spaced elevations. With the development of computing technology, the methods of data acquisition, data storage and data processing speed for DEMs get along well. Heihe river lies in the northwest of China and is a continental river. It roots from snow-ice and disappears in deserts. The drainage area is about 140,000 square kilometers and the river is the main water source for the living. The upper reaches are mountainous and the runoff is very important. The middle reaches are oasis. At present, many hydrological and ecological models are introduced. The catchment basin and stream network data acquired from DEMs are main input data for many surface hydrological models. So the quality and resolution of DEMs are significant. Software ENVI Version 4.2 furnishes with the DEMs Extraction Module. The paper compared several methods for extracting DEMs of the upper reaches. We extracted the elevation data from the ASTER---stereo images with the module and created the DEM. Secondly; we collected the DEM based on the contour map of Heihe river. The comparison of the DEMs quality was carried out between the DEM from the contour map, the DEM extracted by ENVI Version 4.2. To a certain extent, the DEM from Aster imagery can reflect the terrain and be used in hydrological models.