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VALIDATION OF RADARGRAMMETRIC DEM GENERATION FROM RADARSAT IMAGES IN HIGH RELIEF AREAS IN EDREMIT REGION OF TURKEY

In this paper, we describe the technique for deriving digital elevation models (DEM) from a synthetic aperture radar (SAR) stereo pair and apply it to an image pair over the Golf of Edremit in Western Turkey. The objective of this paper is to evaluate DEMs from RADARSAT fine beam mode images as a function of pixel sampling and also of the terrain relief. In addition, throughout the different processing steps the contribution of various effects into error budget (i.e. ground control point acquisition, stereo-model set, image matching and DEM editing) are taken into account.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 lay 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°. The images are orbit oriented, and coded in 16 bits without any radiometric processing. The topographic data were obtained from the Turkish General Command of Mapping. The 10 m counter lines were used to create gray-scaled DEMs, which are then transferred into a 10 m grid file. A corner reflector was installed before the flight and used as a GCP.