I was wondering how exactly does the Underwater GPS Work?
The locator emits an acoustic pulse, which reaches each of the receivers on the boat at slightly different times. The system uses the time difference in the arrival of the pulse, and the known positions of the receivers to determine where the pulse originated, and the position of the ROV relative to the boat is known. The GPS position of the boat is also known, so the GPS position of the ROV can be found by adding the relative position of the ROV to the GPS position of the boat.
Thanks, this clears things up a lot!