COMPARING A STEREOSCOPIC DEM WITH AN INTERFEROMETRIC DEM USING THE SAME RADARSAT DATA PAIR

Abstract

Over the past two decades various studies have discussed and demonstrated the potential of interferometric and radargrammetric DEM generation. The major advantages of radar image pairs over other sources are worldwide availability of satellite data and all weather and day/night image acquisition capabilities. DEMs from radar images can be generated exploiting either the amplitude (radargrammetry) or the phase of the radar signal (interferometry). These two techniques present alternatives to conventional stereo optical DEM generation. This study aims to analyse and compare the results obtained by the two techniques using the same data pair in “sgf” (amplitude) and “slc” (phase) formats. We analyse the quality of both stereo and interferometric results by comparing them to a reference DEM derived from 10 m counter lines. In order to evaluate radargrammetric and interferometric results under various topographic conditions, a study area is chosen over the Golf of Edemit in Western Turkey, which has variety of topographic conditions. The study area overlaps four 1:25 000 scale maps, which is about 50 km by 50 km. The elevation ranges from 0 m to 1767 m. The land cover consists mainly of a mixture of urban areas, agricultural lands and clear-cut areas. The agricultural areas mostly lie in the flat areas and partially take place along the slopes up to 60°. In addition to small rivers, a few loose rivers are also found. The roads are at most dual carriageways surrounding the urban areas. Experiments were done with a stereo pair of RADARSAT-1 data. Two fine beam mode scenes with 6.25 m pixel spacing are acquired with a shallow look angle from descending orbits (F1 and F5) to generate a stereo configuration with a small intersection angle of 8. For interferometric DEM generation one Fine beam data pair (F1-F1) in “slc” format is used. In both cases one of the scenes of data pair is gathered exactly at the same time.