Suitability Assessment of SRTM and ASTER GDEM2 Digital Elevation Model for Terrain Analysis in Aba North: A Case Study of Abia State Polytechnic Aba

Abstract

Accurate geospatial data is fundernental to reliable decision making for sustainable physical development on earth surface. Open-source Digital Elevation Models (DEMs) are imperative to many earths’ surface process analysis therefore it is necessary to subject them to accuracy assessment to evaluate their suitability for different geographical applications. In this study, the elevation quality of DEMs acquired by Surface Radar Topographic Mission of 30m resolution (SRTM-30) and Advanced Spaceborne Thermal Emission Radiometer-Global Digital Elevation Model version2 (ASTER GDEM2) has been evaluated using ground control point captured with digital level and Differential Global Positioning System (DGPS). Two main approaches used to compare the elevation products are determination of the accuracy of the elevation values of the products using 96 ground elevation point (absolute accuracy) and determination of the accuracy of terrain derivatives of the products (relative accuracy). Statistics used to assess absolute accuracy are mean error, root mean square error, correlation coefficient, difference in maximum height, and difference in minimum height. The relative accuracies were assessed by considering similarities between terrain derivatives generated from the DEMS and their equivalence from ground reference.  Results showed that ASTER-GDEM2 has a lower Root Mean Square Error (RMSE = 3. 10m) than SRTM-30m (RMSE = 3.69 m). Further investigation in terms of relative accuracy also revealed that ASTER GDEM2 performed better than SRTM-30 for the study area. Both datasets featured a much better absolute vertical accuracies than the absolute vertical accuracies of 17m (ASTER GDEM2) and 16m (SRTM-30) published in the specification. Although the results of this study may be site-specific, it is an important information that users of the DEMs within Aba north should be aware of, and must be considered into decisions regarding practical applications of these Spatial products. It is also important that the results be considered for the improvement of the next open source GDEM version.