ASSESSMENT OF VERTICAL ACCURACY OF OPEN SOURCE DEMs IN PARTS OF GANGETIC PLAIN REGION WITH ICESat DATA

摘要

Open source Digital Elevation Models (DEM) are very useful in providing an elevation reference for various applications. In Geographical Information System (GIS), DEM provides a terrain model to facilitate drainage network analysis, watershed demarcation, soil erosion mapping, contour generation and for other area and volume calculations. In this study Open Source DEMs namely ASTER, SRTM and CartoDEM are analyzed with ICESat footprints. The selection of DEM is very much dependent on geographical features of earth affecting its quality in the area. The accuracy assessment was carried out for the Open source DEMs with the help of ICESat land altimetry data. ICESat carried a single instrument, Geoscience Laser Altimeter System (GLAS), which measured the travel time of laser returns from the earth surface along profiles, with a spatial resolution of approximately 70 m and an along-track sampling of 172 m (Herring, 1997). It is used to measure ice sheet elevations, change in elevation through time, height profiles of clouds and aerosols, land elevation and vegetation cover and can approximate the sea ice thickness. Total 400 footprints of ICESat data are considered for analysis of elevation derived from Geoscience Laser Altimeter System (GLAS) data. The elevation derived using ASTER, SRTM and CartoDEM are compared with these footprints. These footprints are passing through two districts i.e. Kanpur and Unnao of Uttar Pradesh. All 400 footprints of ICESat /GLAS are divided into six classes for statistical analysis. The result shows that the accuracy is highest in CartoDEM followed by SRTM. The elevation profile of CartoDEM has a better linear correlation as compare to other DEMs. The RMSE value of CartoDEM is varying for different classes from 2.40m (fallow land) to 3.71 m (Built-up area).