Anyone Using Synthetic Aperture Sonar?

I am a retired airborne radar engineer. There is a commonly used radar technology called synthetic aperture radar (SAR) that enables (mostly) military pilots to form a photo-like plan view image of the ground. I've never heard of a sonar analog of this, but perhaps it exists. Range information comes from just measuring the time for the return signal. Cross-range information comes from azimuth-varying return doppler induced by ownship motion. If you are a US citizen I would suggest you enquire with the Naval Research Lab -- they would most likely be the ones doing R&D in this area.