With the successful implementation of ERS-1/2 tandem and SRTM project

InSAR has been wildly used for topographic mapping; in addition

the new global topographic mission such as TanDEM-X project is ongoing. In this paper

firstly

the impact of incidence angle on interferometric SAR DEM generation is detailed investigated from theoretical viewpoint; then

from the ENVISAT/ASAR multi-angle interferometric SAR data

the three DEMs of IS2

IS3 and IS4 swath images are generated using EvInSAR software of EarthView; finally

the impact of layover and foreshortening on DEM accuracy at different incidence angle are compared and analyzed from quantitative and qualitative viewpoints using SRTM DEM with 90m horizontal resolution and digital topographic DEM with 1∶50000 scale. The results indicate that: （1） the impact of incidence angle on DEM generation is significant and large differences exist in the result DEMs due to radar layover and foreshortening at different incidence angle. For example

the difference is over 6m between the DEMs extracted from IS2 and IS4 swath images. So

the incidence angle must be strictly selected when using InSAR for DEM generation in the mountain area. （2） The decorrelation is significant with the 35-day temporal

which is in prejudice of the overall DEM accuracy evaluation. If the data with large incidence angle and no temporal decorrelation is obtained

the further study and analysis will be implemented from more general quantitative and qualitative viewpoints.