Accuracy assessment of radargrammetric DEMs derived from RADARSAT-2 ultrafine mode

The aim of this study is to investigate the accuracy and reliability of radargrammetric DEMs generated from RADARSAT-2 stereo pairs. Two ultrafine mode images U7 and U26 were acquired over an area in Istanbul from descending orbit, HH polarization, in SGF format. U7 and U26 were taken on August 2, 2009 and July 30, 2009 with view angles of 34.0⁰ - 35.3⁰ and 48.5⁰ - 49.5⁰ at the near-far edges, respectively. The main project steps for DEM generation were; 1) Stereo model set up; 2) creating epipolar images; 3) image matching; 4) DEM editing. In order to set up the stereo model, ground control points (GCPs) were obtained from IKONOS image for planimetric information. Also 1:5000 scaled topographic maps were used for elevation information. After the setting up the stereo model with Toutin's 3D physical model developed at the Canada Centre for Remote Sensing (CCRS) and rational function model, radargrammetric DEMs were generated. Root mean square errors (RMSEs) of both GCPs and Independent Check Points (ICPs) were analyzed to evaulate the planimetric and elevation accuracy. Several transects were selected and elevation values obtained from Toutin's and rational function models were statistically compared with a reference DEM. Generated DEMs were also visually compared with Global Digital Elevation Model (GDEM).