GPS technology and diving????

[E Rick]

Someone know if it is possible to use GSP underwater. Is there something under develloppement????


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[Daryl Morse]

Someone know if it is possible to use GSP underwater. Is there something under develloppement????


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GPS does not work under water - period. The signal will not propagate through water.

There is no underwater equivalent of GPS under development either, at least nothing that isn't classified. Submarines use inertial gyroscopes and laser-ring gyroscopes, which are very expensive and have significant limitations. I'm sure if there was an alternative, the navies around the world would be using it, which they aren't.

 

[O2BBubbleFree]

I know I've seen threads on the board discussing GPS and diving, but a search returns 0 results.

As Daryl mentioned, the GPS signals are too weak to penetrate the surface of the water to any useful depth (maybe a couple of centimeters...). However there were discussions on this board about towing a floating GPS receiver above (and behind) you, as well as talk about some other commercial system for underwater triangulation.

Now where did that thread go?????

Addited: Here's some info a google search turned up:

http://www.underwater-gps.com/3uwgps/ugps1.html

 

[ShakaZulu]

I think there could be another way. Using "False Underwater GPS", but instead of a wire, use an electrical cable with a pushbutton interface. On the surface GPS, using strain gauges, you would be able to detect the angle of the cable where it attaches.

At the time you want to mark the spot, push the button. The GPS reading is taken and mathematically corrected with the angle of the cable and the time (distance) the signal travel to the GPS device. You could then calculate the position of the diver exactly.

 

[O2BBubbleFree]

I think there could be another way. Using "False Underwater GPS", but instead of a wire, use an electrical cable with a pushbutton interface. On the surface GPS, using strain gauges, you would be able to detect the angle of the cable where it attaches.

At the time you want to mark the spot, push the button. The GPS reading is taken and mathematically corrected with the angle of the cable and the time (distance) the signal travel to the GPS device. You could then calculate the position of the diver exactly.

'Course, you would have to account for wave action that might change the angle on the cable (rocking the buoy), as well as surface current or wind pushing the buoy in a different direction. I mean, if you have a wind blowing tangent to your direction of tow, the cable could end up in an arc. Right? Maybe strain gauges and gyros? or accelerometers?

Probably be better to devise a low-freq. device that could triangulate your uw position relative to a fixed GPS on the surface. Or would you need three fixed GPSs? Have to think on that one.

Better yet, a low freq. UW transmitter that, when activated, sends a signal that includes a depth gauge reading. Surface unit including GPS and three low-freq receivers triangulates on the signal and uses the depth info to calculate a 3D offset from the GPS reading.

Whatayathink?

 

[The Kraken]

If you have a loooooooooooong antenna and a signal amplifier and a water tight case you could probably do it.
There has been discussion on ScubaBoard about this and there is a company manufacturing something similar to what I described, but I forget the name.
Given the potential underwater applications, it didn't sound too unreasonably priced.

 

[H2Andy]

If you have a loooooooooooong antenna and a signal amplifier and a water tight case you could probably do it.

hmmm... well, i believe submarines can't use GPS under water; they have to use their
internal inertial navigation systems. though, who knows, maybe the Navy has solved
this problem and it's just classified.

for divers, though, it's pretty much a non-issue.

 

[Tom Winters]

SINNS still works fine for the Navy. Sooner or later, someone will run a long wire up to the surface for GPS for divers. At the same time, a radio interface could be added for diver-to-diver comms. The drag from the wire will always be a problem though. Plus it would really be a bummer to get zapped by lightning at 100'.

 

[The Kraken]

The company I mentioned has solved the problem. They make water tight cases for the most popular brands of hand held GPS's and a long antenna lead that leads up to the external antenna left at the surface in a float. There is some type of amplifier (don't know what type, I'm extremely ignorant when it comes to matters of electronics) the boosts the signal down to the receiver. If I remember correctly, the current max depth for the antenna is only about 25 feet or so.

 

[Desa]

***The drag from the wire will always be a problem though. Plus it would really be a bummer to get zapped by lightning at 100'.****

Hey, but it would only happen once.