Underwater Gps localization

[safarir]

Hi everyone,

I was looking at the bp live feed and I notice that the rov have very precise gps location. My question is simple: How do they do that since gps signal don't go underwater ?

Thanks

[DJPhil]

Probably a multiple buoy receiver system that uses acoustic triangulation. The buoy's will know their location via GPS, and will use acoustic signals to communicate with the ROV in a way that somewhat mimics what GPS does with electromagnetic radiation. That's just my guess though.

Here's an example article from a company that specializes in this sort of equipment.