Difference Analysis of SRTM C-Band DEM and ASTER GDEM for Global Land Cover Mapping

Topographic data is one of the fundamental ancillary data for China´s Global land cover mapping project at 30m resolution. SRTM C-band DEM(SRTM for short) and ASTER GDEM (ASTER for short) are two global DEM data sets available, but both have some limitations. It´s nature to combine them together to derive a better DEM with the accuracy of SRTM and morphologic details of ASTER. A difference analysis of SRTM and ASTER in global scale was conducted by the authors using the least squares technique. The result shows that SRTM and ASTER have the best consistency in Australia. A better DEM can be derived by the fusion of these two data sets for about 94% area in Australia. Only 52% area of America has a tolerable difference of these two Data sets. Systematic errors between SRTM and ASTER were evaluated by a hypotheses test with H₀: Systematic errors between them equals to 0. Under significance level α = 0.05, 4% global land areas rejected hypothesis H₀. Specifically 3.4% areas in the north boundary of SRTM(59N~60N strip around the world) rejected hypothesis H₀. So no systematic adjustment is necessary when jointing the two DEMs together. Based on our analysis, a fusion method was proposed in considering of different topology conditions, land cover and consistency of the two DEMs.