Evaluation of Vertical Accuracy of Airborne IFSAR and Open-Source Digital Elevation Models (DEMs) for Flood Inundation Mapping

Abstract

Acquiring an accurate elevation model for flood inundation mapping is essential and can be considered as an expensive task. One possible solution is to acquire readily available digital elevation model (DEM) or open-source DEMs such as ASTER GDEM and SRTM. The issue is how accurate are these datasets and can it be used for flood inundation mapping. The objective of this paper is to evaluate the vertical accuracy of DEMs acquired from different data sources. Results presented in this paper are part of an undergoing research to evaluate the use of global DEMs for flood inundation mapping. For the evaluation of vertical accuracy, DEMs acquired from Airborne IFSAR, ASTER and SRTM Void Fill are used to generate height points. The results obtained are compared with height from GPS observation of two different test sites located in Alor Setar and Kuala Nerang, Kedah. The terrain characteristics of Alor Setar and Kuala Nerang test sites are flat and variable terrain respectively. The overall vertical accuracies of IFSAR DTM, IFSAR DSM, ASTER, and SRTM Void Fill for Alor Setar are ±0.497, ±1.529, ±5.848, and ±4.268 m, respectively. For the undulating terrain, the vertical accuracies of these DEMs are slightly lower, i.e., ±0.841, ±2.092 and ±5.300 m. The height accuracy of ASTER GDEM in undulating area is found to be higher than relatively flat area, i.e., ±3.278 m. Findings from this preliminary test have shown that the vertical accuracy of airborne IFSAR DTM is quite high and can potentially be used in flood management.