Patent ID: 7277042

Claim:
A radar for acquiring a SAR image of radar scatterers in an area around a central reference point, said area having a first elevation and a second elevation, said radar on a moving platform, said moving platform moving along an actual path, said actual path displaced from an ideal path, said radar comprising: an analog to digital converter for converting radar returns from said area to digital returns; a navigation system for motion compensating said digital returns with respect to said central reference point and said actual path; a computer for: dividing said digital returns descriptive of said SAR image into a first strip and an adjacent strip, said first strip covering a first part of said area, said first part having said first elevation, said adjacent strip covering second part of said area said second area having said second elevation, said first strip overlapping said adjacent strip over an overlap portion; extracting said first elevation from a terrain elevation database; extracting said second elevation from said terrain elevation database; computing a first horizontal displacement for said first strip using said first elevation; computing a second horizontal displacement for said adjacent strip using said second elevation; computing Taylor series coefficients using said ideal path, said actual path and said central reference point for said first strip and said adjacent strip; computing phase error compensation using said Taylor series coefficients, a Fast Fourier Transform and an inverse Fast Fourier Transform for said first strip to obtain first strip corrected data and for said adjacent strip to obtain second strip corrected data; applying said phase error compensation to said digital returns to obtain said SAR image.