Comparative Analysis of SRTM and ASTER GDEMs in Topographic and Hydrological Modeling of Onitsha and Environs, Anambra State, Nigeria

Abstract

The aim of this study is to compare and analyze the three most freely available global elevation data set (SRTM and ASTER version 1 and version 2) for topographic and hydrologic modeling of Onitsha and environs using 1:50000 topographic map of the study area as the reference DEM. The contour lines of the topographic map were digitized and their equivalent values used to generate the topographic DEM. The topographic DEM was reclassified and used to determine the impact of terrain configurations on the DEMs. LandSat-7ETM+ was classified and used to determine the influence of landuse/ landcover on the DEMs. Hypothesis testing was used to determine the most suitable datasets for topographic and hydrological modeling in the study area using the ztest statistical analysis. SRTM was tested against ASTER ver1, and ASTER ver2. ASTER ver2 was tested against ASTER ver1. The study revealed that there is enough evidence to support the claim that elevation values obtained from SRTM is a better representation of the earth surface than ASTER ver1. Also, the hypothesis testing between SRTM and ASTER ver2 revealed that there is enough evidence to support the claim that elevation values obtained from SRTM is a better representation of the earth surface than ASTER ver2 dataset. For hypothesis testing between ASTER ver2 and ASTER ver1, the study shows that there is not enough evidence to support the claim that elevation values obtained from ASTER ver2 dataset is a better representation of the earth surface than ASTER ver1. The result of the hypothesis testing revealed that SRTM is most suitable for topographic and hydrological modeling in Onitsha and Environs. The study recommends the use of SRTM for topographic and hydrologic modeling of Onitsha and Environs and other areas of similar topography representation.