DEM generation from radarsat stereo images in high relief areas

DEM (Digital Elevation Model) generation from spaceborne SAR stereo images is an effective and economical means for the purpose of topography mapping. The radartgrammetry technique shows the perspective of application in the perennial cloud-covered areas. Radarsat provides plentiful SAR stereo images pairs which can be used to generate DEM with radargrammetry technique because of its variety of beam modes and variable incidence angles. Up to now, development of algorithm and methods for generating DEM from SAR stereo image pair is still main research topic. In this paper, we describe the methodology for deriving DEM from Radarsat stereo image pairs. We adopt the methodology that we uses the satellite ephemeris data, ground control points (GCPs) data, earth ellipsoid model, cartographic projection parameters and the range projection characteristics of SAR image to calculate the three dimension coordinates of ground points. The horizontal and the vertical coordinates of ground points are calculated separately, the elevation calculation is based on the parallax of homologous image point, the planimetric coordinates calculation is based on the calculated elevate and SAR image geometry model. We demonstrate the methodology with Radarsat stereo pair (W2-S7) over high mountain areas in southwest China. The image coordinates of GCPs used in the experiment are acquired by two manners: from stereoscopic viewing and from monoscopic viewing, the accuracy of results from using two groups of GCPs’ image coordinates respectively are compared. The accuracy of final result is analysed and assessed. The experiment illustrates the methodology adopted in this paper is operational and radargrammetry is a feasible technique of obtaining topography data in many areas especially where conventional optical system has difficulty in acquiring images. Key words-Digital Elevation Model (DEM), SAR, stereo images, radargrammetry, methodology