Accuracy validation of the IFSARE radar system

The validation of a radar system for making topographic measurements is described. The system is an interferometric SAR radar flown by Norden Systems in late 1992 and early 1993 under an ARPA-sponsored program. Both absolute and relative height measurements were made, with aircraft position referenced to an INS/GPS and a separate differential GPS. An initial accuracy prediction was obtained from a complete system error analysis. Confirmation of this prediction was a non-trivial task, which consisted of making comparisons with truth models obtained using photogrammetric surveys, using over-water measurements, and using radar data collected from orthogonal night directions. A photogrammetric survey was performed over a 5 km square area, with residual photogrammetric height errors estimated at less than 1 foot. The size of the survey area was considered large enough that radar system stability could be assessed. The inclusion of four-way corner reflectors in the surveyed scene permitted radar measurements to be tied to the photo-surveyed points so that the image scale factor could be determined. Radar system stability was also assessed by mapping the ocean surface. Both phenomenological and system limitations in accuracy are addressed