Open source tools are the freely available tools for the analysis of remote sensing data such as QGIS, SAGA GIS, GRASS GIS, and others. In the present study GLAS visualizer GUI open source tool has been used for analysis of ICESat spaceborne Lidar data which runs on IDL virtual machine. This tool has been coded in IDL (interactive data language). For the extraction of elevation from GLA14 binary file NSIDC GLAS Altimetry elevation extractor tool (NGAT) has been used. All other tools for the GLAS related data are open source and available in the NSIDC official website.Open source DEMs are available with global coverage such as GTOPO, SRTM, ASTER, and also with countrywide coverage like CartoDEM for Indian region.This study aims to evaluate accuracy of the latest release of open source CartoDEM i.e. V2R1 and ICESat spaceborne Lidar i.e. V34 over Dehradun and adjoining areas in Uttarakhand. GCPs derived from differential GPS (DGPS) survey are also used for accuracy assessment at sample locations. Elevation derived from ICESat product GLA14 has been compared with the elevation derived using DGPS data as well as CartoDEM, ASTER & SRTM elevation. The results show that the elevation values on the relatively flat terrain have less difference between actual surveyed values and ICESat elevation values. The large differences in the undulating rough terrain can be attributed to the slope of the highly undulating terrain within the footprint. The CartoDEM values are used to compare the elevations for over 400 footprints. The RMSE values for agriculture and forest area are 5.50m & 11.93m respectively for CartoDEM elevation. RMSE value was found to be quite high in steep terrain for primarily due to large footprint.
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