Vertical accuracy validation of digital elevation models (DEMs) in Shikoku Island, Japan

Digital Elevation Models (DEMs) on free provided data including Shuttle Radar Topography Mission (SRTM) and Advanced Space borne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM) are used to model nearly the surface of earth. DEMs have made a high accuracy to assess an error using an observation elevation point. In this study, DEMs at original spatial resolution which are the SRTM version 4.1 (SRTM v4.1) and the ASTER GDEM version 2, (ASTER GDEM2) were evaluated and corrected by using a ground control point (GCP) that was observed by global position system (GPS). The Sikoku Island in Japan was selected for evaluation and correction of the DEMs, based on statistical measurements and transformation adjustments. The statistical measures were analyzed from differential elevation between the GCP point and the corresponding DEM pixel. Root mean square error (RMSE) was estimated for DEMs validation and frequency histograms and quartile-quartile plots were applied to evaluate error distributions on each DEM. In the correction approach, transform's parameters on coordinate (x, y and z) were estimated by using the GCP point and the corresponding DEM pixel, based on affine transformation method with least square method for minimization to estimate optimization parameter. The results indicate that the ASTER GDEM2 is higher than the SRTM in the vertical accuracy, while both DEMs have gotten more accuracy after corrected by the transform's parameters. The RMSE of SRTM is 10.084 m and 9.933 m for the ASTER GDEM2 on the existing vertical accuracy. On the transformed DEMs, 9.312 m is the RMSE of SRTM and 9.084 m for the ASTER GDEM2. The approach proposed will be used to adjust the DEM for high accuracy to model the earth's surface.