Spatial Distribution Of SRTM DEM And ASTER GDEM Error

As the input data of geo-science analysis, DEM's accuracy restricts the accuracy of the analysis results, affects the reliability of decision. Therefore, DEM accuracy evaluation is one of the important research content of geo-science analysis. SRTM DEM and ASTER GDEM are the most popular DEMs for high precision, high resolution and open access characteristics. Many scholars have evaluated their accuracy,but focused on the small and medium regions, typical terrain, and have not studied the accuracy and error spatial distribution of SRTM DEM and ASTER GDEM in China as a national region.In this paper, the GLA14 elevation is assumed as the true value to statistical analysis the error distribution of SRTM DEM and ASTER GDEM under the terrain factors (slope and aspect), surface features (Global Land Cover Climatology and Maximum Green Vegetation Fraction), terrain feature lines (ridge and valley lines).Studied the spatial distribution of SRTM DEM and ASTER GDEM errors in China by using the equal latitude and longitude method and studied the spatial variation of SRTM DEM and ASTER GDEM errors in China by using equal area method and semi-variance analysis method. The main research contents and achievements are as follows:1) The spatial distribution characteristics of SRTM DEM and ASTER GDEM error in land area of China. The spatial distribution of SRTM DEM error is diamond-shaped in the flat area, and has a strong correlation with the terrain in the complex terrain. The spatial distribution of ASTER GDEM error form zonary pattern, which direction is from northeast to southwest,and has a weak correlation with terrain.2) The distributing disciplinarian of SRTM DEM and ASTER GDEM error under surface features' influence. This paper selected global land cover climatology and maximum green vegetation fraction as surface feature data to study its influence on DEM error distribution. The results show that the SRTM DEM and ASTER GDEM errors are quite different in different global land cover types, and relate to the maximum green vegetation fraction which increase with the maximum green vegetation fraction increasing.3) The distributing disciplinarian of SRTM DEM and ASTER GDEM errors under the terrain feature lines' influence. This paper discussed the distribution of DEM errors from slope, slope direction, ridge line and valley line perspective. The results show that the error distribution of SRTM DEM and ASTER GDM has a strong correlation with slope, slope direction and distance from valley ridge line. The error of SRTM DEM and ASTER GDEM increases with the slope and their distributing disciplinarian is opposite in slope direction, distance from the ridge line and the valley line.4) The spatial variation of SRTM DEM and ASTER GDEM errors. Study the spatial variability of SRTM DEM and ASTER GDEM errors under the effects of orbital running direction, terrestrial ecotype and vegetation coverage. The results show that the semi - variance of SRTM DEM and ASTER GDEM errors increase with the distance increasing. According to the stable semi-variance, the terrestrial ecology type can be divided into three types: high, medium and low, and the terrestrial ecotype is the same in one classification. The spatial variability of SRTM DEM and ASTER GDEM errors with low vegetation coverage in a terrestrial ecological type is greater than that of high vegetation cover.5) Compare and analyze the spatial distribution of SRTM DEM and ASTER GDEM errors. The error distribution of SRTM DEM and ASTER GDEM is analyzed from three aspects: error distributing disciplinarian, error spatial distribution and error spatial variation. The spatial distribution characteristics between SRTM DEM and ASTER GDEM error are different, but the distributing disciplinarian and spatial variation of SRTM DEM and ASTER GDEM error are similar. In same conditions,SRTM DEM error is smaller than ASTER GDEM, and the spatial change is smaller,too.