Accuracy evaluation of ALOS DEM with airborne LiDAR data in Southern Taiwan

Recently, some global-scale DEM products, such as GTOPO30, ETOPO1, SRTM and ASTER GDEM have been published for geoscience applications. The latest product, ALOS DEM was announced to be available for a global coverage in 2016. This study examined the performance of ALOS-DEM in describing accurate morphometric and volumetric measurement of land features. A comparison was made on basis of DEM and DSM data of airborne full-waveform LiDAR data. Results showed that ALOS DEM is more approximately in reality an ALOS DSM which reveals the ground envelop surface rather than the ground bare surface. The differences between ALOS DEM and LiDAR DSM are mainly from 0 to 2.75 m with a standard deviation of 1.58 m. The differences between ALOS DEM and LiDAR DEM give a bias of as large as 20m, mostly located at the areas with abrupt change of relief and mainly in the north-facing slopes. This is probably due to ALOS sensor's geometry in corresponding to its looking-direction. The stream networks derived from both ALOS DEM and LiDAR DEM are in good agreement. It is suggested that further studies on methods for assessing geomorphometric changes in landform structures should be developed and compared.