Gps???

[FFMDiver]

If surface-to-diver communications systems hang a receiver in the water to pick up divers voices, why cant they do the same for GPS systems????

 

[DennisS]

bmuise once bubbled...
If surface-to-diver communications systems hang a receiver in the water to pick up divers voices, why cant they do the same for GPS systems????

You could put the receiver on a float and send the data by wire down to a waterproof display. The receiver antenna has to be visible to the satellites. The satellites send down very weak signals that won't penetrate water, heavy foilage will sometimes block the signal.

 

[FFMDiver]

I understand satellite signals cant penetrate water.

My question is, if wireless comm systems use a base station and send signals from the comms to the base station (wired to the boat) why not use the same wireless signals to rerlay coordinates from a base station on the surface?

 

[DennisS]

bmuise once bubbled...
I understand satellite signals cant penetrate water.

My question is, if wireless comm systems use a base station and send signals from the comms to the base station (wired to the boat) why not use the same wireless signals to rerlay coordinates from a base station on the surface?

it would have to be directly above the diver all the time to give the diver's position.

One common method of U/W position fixing involves dropping 3 accoustic pingers at known locations, the position of the U/W object is triangulated from these transponders. It could be a diver, camera or free floating current measuring device.

 

[El Buzo Loco]

Haven't tried this and wonder if it might be a cheap solution:

Pack a small Garmin etrek or emap into a clear dive-rated transparent case. Have it be slightly positive buoyant.

Send it up on a line (using a reel) and allow it a minute or so to get its position.

Pull it down and read the coordinates.

 

[KrisB]

El Buzo Loco once bubbled...
Haven't tried this and wonder if it might be a cheap solution:

Pack a small Garmin etrek or emap into a clear dive-rated transparent case. Have it be slightly positive buoyant.

Send it up on a line (using a reel) and allow it a minute or so to get its position.

Pull it down and read the coordinates.

Sure... but how precise do you need it? If you're 50' deep and there is a very, very slight amount of current, waves, etc, your line might be at a 1 degree angle. You're already out about a half-foot.

Let's say you're looking at more severe conditions. You're in a place where there is some current, in addition to waves. Now, the waves are likely heading for shore, the current parallel to shore. Assuming your line, when taught, is only at 10 degrees, you're out five feet, though you don't know which direction, really. So, you have a rather large circle in which to search for that same position.

What is the goal of using the GPS? To find lost treasure when you come back with a lift bag? Don't count on it. To find a rough estimate of where you were... ok, sure.

 

[Jai Bar]

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

I have a similar idea that works with a diving computer like a Vyper/Vytec, where one can add tags to the profile (e.g. each time the "Plan" button is pressed you'll see a mark in the profile).

Next, one can buy for about 30-50$ a GPS-datalogger receiver. These things are commonly used in vehicles and many other applications. They are cheap because they don't have a LCD display or special features and gimmicks, they just log coordinates at specific intervals, which can be loaded to a PC (or one can integrate them in whatsoever application he likes).

The GPS receiver can be placed in a watertight case and tugged along the dive, using a spool. One can add a mark to the DC's memory every few minutes, or when something interesting comes.

Then, after downloading the DC's profile and GPS datalog, one can synchronize the markings on the profile with its coordinates from the GPS (simply comparing the DC's time and GPS time. IMO if one sets the same time even with a few seconds erros is not a problem).

So, one now knows the depth and time from the DC, and the Long/Lat coordinates from GPS, putting them together we have 3D plotting of the dive site. For practical purposes I don't think that one needs a resolution better than 10-20 meters, so even if the buoy is biased because of waves or current, it shouldn't be so critical.

 

[FFMDiver]

Now thats an interesting setup....

I would like to even see something that could be a pinger that attaches to the anchor line and a receiver that goes into your console that has a flashing light that told you you were getting closer or farther away...hot or cold type deal...allowing you to merely find the boat...

 

[Charlie99]

bmuise once bubbled...
I would like to even see something that could be a pinger that attaches to the anchor line and a receiver that goes into your console that has a flashing light that told you you were getting closer or farther away...hot or cold type deal...allowing you to merely find the boat...

http://www.scubadiving.com/gear/11navdevices/locators.shtml

 

[FFMDiver]

Thank you so much.
I see them. This is great!