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.