Research on the Mathematic Model of Direct Geolocation with Airborne SAR Image

This paper obtains a mathematic model of direct geolocation in uncontrolled circumstances, by using DGPS(Differential Global Positioning System) and attitude measurement data for Airborne Synthetic Aperture Radar(SAR) image. Firstly, coordinate transformation, dynamic eccentric correction and interpolation of antenna phase center is done by using DGPS/INS(Inertial Navigation System) data for determining position and attitude of radar antenna phase center on each scanning beam of along-track. According to Range-Doppler(R-D) Model and Digital Elevation Model (DEM) data, geographic coordinates of every point is calculated in Airborne SAR image, then ortho-image is obtained by resampling. Through the experiment of direct geolocation with one-meter resolution airborne SAR images in Chengdu study site, correctness of the mathematic model is validated, and the sources and correcting methods of main systematic errors is analyzed.