Corrected Precision of Topographic Measurements by Radar Interferometry

This communication presents a corrected formulation, differing significantly from a traditional and widely employed one, for the precision of topographic measurements by means of space-based or airborne radar interferometry. The reasons for the differences are explained. The results are applicable to both downlooking topography and conventional geometries for interferometric synthetic aperture radar. Comparisons between the opposing formulations are exhibited for interferometer baseline tilt angles relative to the horizontal of five and sixty degrees. The discrepancies are especially wide at near-nadir viewing. The corrected formulation for measurement precision is presented in both its exact form and a convenient approximate expression, the two differing by less than one percent for the spaceborne interferometer illustrated.