1. A radar for acquiring a synthetic aperture image of a scene on earth, said earth having a great circle centered with respect to said earth's center, an axis passing through said earth's center and a first radius, said great circle contained in a first plane, said scene having a radar scatterer, said scene on said earth, said scene adjacent to said great circle on a local scene centerline circle, said centerline circle in a second plane, said second plane parallel to said first plane, said centerline circle having a second radius, said second radius smaller than said first radius, said radar system mounted on a moving platform moving with a component of motion in a direction along said great circle, said radar comprising: a radar receiver for digitizing radar returns having a phase from said scatterer in said scene, and a computer for focusing said phase of said radar returns from said scatterer in said scene, said phase of said radar returns received from said scene focused for the motion of said moving platform along said great circle using cylindrical coordinates; computing said synthetic aperture image from said radar returns; making an initial position estimate of said scatterer within said synthetic aperture image using said cylindrical coordinates; converting said initial position estimate from said cylindrical coordinates to geodesic coordinates of initial latitude, initial longitude and initial elevation; extracting a second elevation from a database descriptive of earth's surface at said initial latitude and initial longitude location; replacing said initial elevation with said second elevation; computing a second target location within said synthetic aperture image using said second elevation; comparing said second target location with said first target location to obtain a difference; replacing said second target location for said initial position estimate if said difference is greater than a threshold; repeating said converting step, said extracting step, said computing step said comparing step and said replacing step until said difference is less than said threshold.