snatcher 2 announcement out, page-15

Indead seismic (2D or 3D) is like an echo sounder or Sonar (or for that matter Ultrasounds and Radar)

Same principle - compression waves travelling through a medium bouncing off a reflector and returning to a reciever where the time is noted. The refinement is how the time of the return wave is turned into an airplane trying to land, fish/sea bottom or a camera flash and a ticket.

3D and the new 3D ultrasound use multiple recivers and sometimes multiple source to let a computer algorigm attempt to build a picture of the body being probed.

Petroleum seismic using 3D is by far the most complicated of all these proceedures since waves 'spread' and 'scatter' and do all sorts of things you dont want to see the mathematics of, while they travel kilometers through the earth bouncing off this and that in the folded and faulted geology that is likely to trap oil.

By contrast a radar gun is a light wave (well known speed which is unbreakable at least according to Einstein) travelling through a uniform medium (the air) bouncing off your speeding car and back to the receiving unit. The variation due to elevation is calibrated and the small variation due to changes in smog, air pressure and rain amounts to less than a 2% variation in accuracy of a radar gun.