Improving quality of public domain digital elevation models through data fusion

Abstract

Digital Elevation Model (DEM) fusion was investigated for improving the overall accuracy of DEMs. The approach was applied to two public domain products: Shuttle Radar Topographic Mission (SRTM) DEM and Advanced Spaceborne Thermal Emission and Reflection (ASTER) DEM. The ASTER relative DEM was co-registered to the SRTM co-ordinates and converted to an absolute DEM by shifting the histogram to the average elevation of the SRTM DEM. The voids in the DEMs were filled through an erosion technique using the slope and aspect from the other DEM and the elevation of surrounding pixels. Finally, the DEMs were converted to the frequency domain and an ideal low-pass filter with a cut-off frequency of 0.024 m −1 was applied to the ASTER DEM and a high-pass filter with the same cut-off frequency was applied to the SRTM DEM to filter out errors in the respective frequency ranges. The filtered DEM spectra were then summed in the frequency domain before being converted back to the spatial domain. This approach was tested in a 6000 ha test site with fairly complex topography located in the central region of Nepal. The fused DEM had a 42% improvement in Root Mean Squared Error (RMSE). The approach showed promise for improving DEM accuracy and completeness while maintaining the highest resolution of the input DEMs. This approach increased the reliability and applicability of public domain DEMs produced by Optical and Radar remote sensing technologies.