SOUND METRICS: http://www.soundmetrics.com/about-sonar-imaging

Sonar is pretty old technology but theres a really cool company doing high end imaging versions of it that go far beyond detecting torpedos and submarines in the water.

A sonar imager or scanner essentially just has an emitter and a receiver and a processor. The emitter emits sound, and the receiver receives it. The processor determines the attenuation and the delay of the reflected impulse signal to determine how far away the object is. Do this enough over a large area several times from a few directions and you get co-ordinates to the object’s surface which you can then make surfaces/meshes out of.

Here is a 3-d scan of a submerged fallen bridge structure at the bottom of a river, taken with a sonar imager.

Some cool gifs of Lamprey getting scanned from 5 metres away in really really dark water.

Also check out this link of debris from the bottom of the Atlantic (of the Titanic) getting scanned with Sonar Imaging : http://www.dailymail.co.uk/news/article-2112456/Titanic-pictures-Extraordinary-sonar-images-map-shipwreck-ocean-floor.html

They combined it with low-light underwater robotic photography to make a really intense map of the shipwreck. 

The good: Using auditory sound to generate visual images is such an engaging concept to my inner printmaker. The synaesthesia involved in this process involves so much translation of data between different processes (that analyse the attenuation, delay, direction…)… it is pretty impressive that we can actually do it without very much technology involved. Whales, Bats and Dolphins use it, so it has to be pretty useful. Especially when light isn’t available. You can also scan really big things.

The bad: Sonar is nasty in terms of noise, movement and random refractions/reflections that mess up with the actual reflected wave data that the receiver is supposed to collect. Its also expensive. And doesn’t really work on small objects because sound has a pretty big wavelength (compared to light).

If you like what you’re seeing ( I sure do), then you probably should buy one of the sonar cameras: http://www.soundmetrics.com/products/imaging-sonars/didson-300