Document Type: Original Article
School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran, Tehran, Iran
The Synthetic Aperture Radar (SAR) geometry imaging includes geometric distortions, which cause errors. To compensate the geometric distortions, the information about sensor position, imaging geometry, and target altitude from ellipsoid should be available. In this paper, a method for geometric calibration of SAR images is proposed. The method uses Range-Doppler (RD) equations. In this method, the georeferencing is carried out using the Digital Elevation Model (DEM) and also exact ephemeris data of the sensor. First, the digital elevation model is transferred to the range and azimuth directions. Then, the original image is registered to the transferred DEM from the previous step with transformation equations: conformal, affine, and projective. The advantage of the method described in this article is the elimination of required control points and rotational parameters of the sensor. Since the ground range resolution of used images is about 30m, in best stance, the geocoded images using the method described in this paper have an accuracy of about 20m (subpixel) in planimetry and of about 33m in altimetry.