In the spirit of looking at 3D imaging as being more than just laser scanning this post on Julians Blog has a nice intro to the basics of using sonar to map, in this case underwater volcanoes. For those not familiar with the technology sonar uses sound waves, or acoustics to determine the range or distance to the object. The return acoustic signal is then processed to determine the contours. In general the analysis is much more complex than found with laser scanning, more like full waveform analysis of LiDAR.
