Precise Rectification of SAR Images
SAR影像的几何精纠正

With the development of SAR(Synthetic Aperture Radar) remote sensing techniques,SAR images have been widely applied in a lot of fields.But because of its side-looking character,we have to rectify the images into orthoimages before we use them.Building mathematical models is an important step in SAR rectification.In this paper we first recapitulate some mathematical models used for SAR image rectificaion,including Soviet Model,Polynomial Model and G.Konecny Model.The characteristics of these models are analyzed.Then we introduce the F.Leberl Model in detail,which is based on the distant condition and the zero-Doppler condition.In airborne condition the range direction is perpendicular to the flight track so the Doppler center frequency is zero.But in spaceborne condition,the Doppler center frequency does not always equal to zero,so the zero-Doppler condition needs to be corrected.In this article we use a polynomial to substitute the value of the Doppler center.By this way we corrected the zero-Doppler condition.In the experiments we used both the original F.Leberl Model and the corrected model to validate the precision of our model.From the results we come to the conclusion that the new model is acceptable to both the airborne SAR and the spaceborne SAR,at the same time it can get higher precision than the original model in spaceborne condition.