Adjusted SRTM DEM of Owerri, South East Nigeria
Global Positioning System (GPS) Fast Static survey was used to coordinated 69 ground control points across the project area, which was a terrain of less than 6% slopes. Elevations of the control points were referenced to the same EGM 96 geoid as the SRTM 3 arc seconds (3") DEM. Errors of the SRTM (3") DEM were determined at the control points by subtracting the elevations of the control points from those of the SRTM DEM. An adjustment surface Raster was constructed for the SRTM (3”) DEM using kriging interpolation. The adjustment Raster was applied to the SRTM (3”) DEM of Owerri, South East Nigeria and it resulted in an adjusted SRTM dataset over the project area with error statistics reduced from average of -4.34 m and RMSE of ±4.90 to -0.17 m and RMSE ±2.42 m.
Steps to reproduce
1) Download SRTM DEM over area of interest 2) Set up Global Positioning System Control Network over the project area referenced to the EGM 96 geoid. 3) Subtract the elevation of each GPS control from the corresponding SRTM (3”) to determine the SRTM (3”) errors at the control points. 4) Use kriging interpolation on the determined errors at the ground control points to create an SRTM (3”) DEM adjustment surface Raster of matching cell registration with the published SRTM (3”) DEM. 5) With Raster mathematics operations subtract SRTM DEM adjustment surface from the published SRTM DEM to create the adjusted SRTM DEM of the project area. 6) Using another set of control stations across the project area check the error status of the adjusted SRTM DEM and note the error statistics