Shore-based  measurements use Inverse SAR imaging. The ship is navigated in a circle, very slowly and hopefully in calm waters to avoid excessive roll and pitch, while the radar data is collected. This can take 20-30 minutes, although there is often enough time to permit the radar to collect data in several bands at the same time. The resulting data is then processed into images that provide the radar cross section of all elements of the ship, down to the resolution of the radar (typically 10 cm to 1 meter). In order to measure additional elevation angles, the ship must sail a circle at a different range. Because the range of the ship from the shore site is long and varies, it is often necessary to have several large radar antennas for each radar band measured.

      Airborne measurements are made by flying the aircraft (or helicopter) in a circle about the ship at the altitudes required for each desired elevation angle. The radar can also be flown on trajectories that match the trajectories of anti-ship missiles to provide data to evaluate actual seeker performance. Airborne antennas can be relatively small because measurement ranges are relatively short. METRATEK has developed a very fast waveform that greatly simplifies airborne ship measurements and techniques that permit the height of targets in 2-D images to be measured.

      Airborne measurements are much less expensive than shore based measurements because the expense of a large land site are avoided and the aircraft can go to the ship, instead of vice-versa.