Abstract: Synthetic aperture radar data is used to produce a terrain map. Two synthetic radar antennas are placed on an aircraft, which moves in a set of substantially parallel flight paths. At least one antenna repeatedly transmits radar signals whose return echoes are received by both the antennas. The echo signals are processed conventionally to yield slant range and Doppler frequency data for plural resolution cells. The measured phase difference for each resolution cell provides an ambiguous measure of slant range difference to the two antennas needed to determine terrain elevation and correct ground range. As in the prior art, the radar transmissions employ an extended bandwidth of wavelengths. The received echo data is reprocessed using less than the entire bandwidth of the radar transmission to achieve additional center wavelengths. This produces a differing ambiguity interval and permits unambiguous determination of the slant range difference.