Corrected Precision of Radar Interferometry for Topographic Estimation

This manuscript corrects a longstanding formulation of the precision of interferometric measurements of the height of topographic features. This communication presents a corrected formulation, differing significantly from a traditional and widely-employed one, for the precision of topographic measurement estimates by means of space-based or airborne radar interferometry. Comparisons between the different formulations are exhibited for interferometer baseline tilt angles relative to the horizontal of five and sixty degrees. The reasons for the differences are explained. The results are applicable to both downlooking topography and conventional geometries for interferometric synthetic aperture radar. The discrepancies are especially wide at near-nadir viewing, which is the case for a current satellite program. The corrected formulation for estimation precision is presented in both its near-exact form and a convenient approximate expression, the two differing by less than 0.1 percent for the parameters illustrated for a spaceborne interferometer.