Is there such a thing as under water GPS?

[scuba_moron]

Hello,

Is there such a thing as under water GPS. It would make navigating a whole lot easier.

 

[EastEndDiver]

No.........

 

[NSDiver]

No...

...and I don't see how that could really make navigation easier...

 

[GrumpyOldGuy]

Not to my knowlegde. Radio waves of a reasonable length don't penetrate water very far. That leaves inertial (gyro) navigation systems, which are too complex and costly for recreational use.

 

[Gary D.]

Yup, It's called a Compass.

Gary D.

 

[MSilvia]

Well... yes, but it's not a simple hand-held unit like on land. GPS signals don't penetrate water very well, so in order to make underwater positioning effective, you need to be able to figure your underwater position relative to a known location via other means. For example, you could use acoustic signals to "ping" a series of buoys that had GPS data for their locations, and have each buoy relay data to a computer that could triangulate your position relative to those buoys based on the time it took each of them to recieve the signal. Then, the computer could relay that information back to you.

Of course, it's a cost and logistics intensive solution, and similar systems have run into problems in the past when curious bottlenose dolphins started mimicing the acoustic "pings", causing erroneous data to be introduced.

 

[WetDawg]

The short answer is RF radio waves to not travel well through water, so GPS will not work while actually underwater. The are a couple super expensive military style products out there, but most divers are not looking to spend "Space Shuttle Money" on such things.

However, there is a another option - you can use your regular handheld GPS unit while diving by floating it in a waterproof box on the surface attached to your dive flag line. There a couple excellent explanations of how to do this out on the web. I have tried this a couple times on shallow beach dives and it works surprisingly well.

In a nutshell, this system works because though the unit will not get a signal while underwater, it will display the last good position... so.... the basic idea is to swim with the GPS in a clear waterproof box (pelican or otterbox) tied on the other end of your dive flag line. when you find a spot you want to mark simply allow the box and gps unit to float to the surface - give it a couple minutes to get a new signal, then reel it back down and write down your new position on your slate. It's that simple. If you mark your start location (like your boat) at the beginning of your dive while on the surface and use your units "go to" function, each time you send it up for a "fix" it will give you the heading and distance to your start position as well.

Pretty cool, eh?

The best explanation can be found here:

http://groups.msn.com/divergps

Another way here:

http://www.wadespage.com/D800DS07RF00.shtml

And the best is here:

 

[kirwoodd]

Hello,

Is there such a thing as under water GPS. It would make navigating a whole lot easier.

I read somwhere about a dood putting a GPS in a dry bag and running an antenna to his marker. As I recall it was theoretical, but it COULD work if you kept the GPS dry and you could extend the antenna that far....

I prefer a reel.

 

[kirwoodd]

The short answer is RF radio waves to not travel well through water, so GPS will not work while actually underwater. The are a couple super expensive military style products out there, but most rec. divers are not looking to spend "Space Shuttle Money" on such things.

However, there is a another option - you can use your regular handheld GPS unit while diving by floating it in a waterproof box on the surface attached to your dive flag line. There a couple excellent explanations of how to do this out on the web. I have tried this a couple times on shallow beach dives and it works surprisingly well.

In a nutshell, this system works because though the unit will not get a signal while underwater, they will display the last good position... So.... the basic idea is to swim with the GPS in a clear waterproof box (pelican or otterbox) tied on the other end of your dive flag line. when you find a spot you want to mark simply allow the box and gps unit to float to the surface - give it a couple minutes to get a new signal, then reel it back down and write down your new position on your slate. It's that simple. It you mark your start location (like your boat) at the beginning of your dive and use your units "go to" function, each time you send it up for a "fix" it will give you the heading and range to your start position as well.

Pretty cool, eh?

The best explanation can be found here:

http://groups.msn.com/divergps

Another way here:

http://www.wadespage.com/D800DS07RF00.shtml

And the best is here:

oh.
much better idea.
Never mind then....

 

[MSilvia]

In a nutshell, this system works because though the unit will not get a signal while underwater, it will display the last good position... so.... the basic idea is to swim with the GPS in a clear waterproof box (pelican or otterbox) tied on the other end of your dive flag line. when you find a spot you want to mark simply allow the box and gps unit to float to the surface - give it a couple minutes to get a new signal, then reel it back down and write down your new position on your slate.

Of course, if there's a current and you're at depth, the last "good position" could be a substantial distance from your actual position.

You could carry a protractor, compass, and a watch though. If the GPS time and your watch were synchronized, you could note the time, depth, angle of the GPS line, and it's heading relative to your position, then check the GPS post-dive for it's position at the noted time and calculate how far away you were from it and in what direction. It wouldn't help much for mid-dive navigation, but it could help you get back to that treasure chest.