Orthographic calibration of space-borne ALOS PALSAR microwave remote sensing image in mountain area

the ortho-rectification of SAR (synthetic aperture radar) is difficult and a key step for its final application especially in mountain area. However, the method of the ortho-rectification of SAR is not available in the current remote sensing software. In this paper, the ortho-rectification of microwave remote sensing image was conducted based on GAMMA software platform and ALOS PALSAR basic data. Firstly, the simulated SAR image was generated by means of DEM (digital elevation model) and the satellite orbit parameter. Then, the registration offsets between the simulated SAR image and the real values were determined automatically using cross correlation analysis, and the polynomial models of these offsets were built accordingly. Finally, the true SAR image was resampled from the SAR with range and azimuth coordinates to one with the orthonormal map coordinates using a lookup table, which was generated by comparing the simulated and real SAR image and refined by the offsets registration polynomials. The accuracy of registration was tested by comparing with topographic map, and rectification errors were less than one pixel, which is less than 20 m.