Marking GPS Waypoints While Diving

[Afakasi]

Does anyone ever try to mark spots with a GPS while diving? I found a very brief article online that talked about a low-tech way of doing this. The article mentions carying a handheld gps inside of a bouyant container while diving, and then floating the container to the top in order to get a signal when you want to mark a spot. Has anyone ever tried this or any other way of marking GPS locations? Would the pressures affect electronics in any way? I am a new diver who has visions of diving the lakes that I fish and marking the best structure for later fishing.

Thanks in advance for any feedback.

 

[mike_s]

I've never tried it.... but any mooring line coming off a sunk wreck usually has a slight tilt to it based on the current...

so I imagine a GPS buoy on the surface would not be directly above the diver either, but slightly down current.

just like when you tow a dive flag, it always trails slightly behind you.


just pointing this out because it will cause an offset in getting a true accurate GPS fix of your position. (in my opinion).

 

[Teamcasa]

I just mark it when I'm on the boat. Then Google map it when I get home.

 

[ScubaSteve]

I have read about people doing that on long swims to ensure that they are heading in the right direction. Depending on what you want with the numbers, I am sure it will work just fine. If you are just looking to mark the area in general so you can get back close, then go for it. If you want accuracy, I would suggest marking the point in the boat and write down the direction and strength of the currents.

 

[simcoediver]

Ive used it a few times, I put my small handheld GPS into 2 heavy duty ziplock bags and tow it in an innertube type flag holder till I find the wreck . This was discussed in detail a couple years ago on scubaboard. Heres the link http://www.scubaboard.com/forums/archive/index.php/t-215000.html

 

[Afakasi]

Thanks simcoediver, the link to the e-book was very informative.

 

[don Francisco]

I'm sorry, I don't get the need, unless you're using a DPV. Otherwise scuba diving doesn't involve swimming great distances.

If you use GPS on the surface to locate your starting point, you can use traditional UW navigation (course and speed & time) techniques to track movement from that point. With decent skill you should be able to know where you are within the same margin of error as handheld GPS units afford.

 

[Gen San Chris]

If we need GPS Points we usually send up a buoy of some kind then take the GPS Point from the boat! GPS is not perfect anyway unless you have a professional set up but it gives you a pretty near point for reference!

 

[miketsp]

I mentioned this on another thread recently. I occasionally use my Blackberry with a very nice logging SW called BBTracker. This logs the GPS chip output every 5 seconds to a file and this file can be exported to a KML format. This can be read-in by Google Earth and plotted very nicely.
I have one of those small waterproof key/document holders in a flat format that accepts quite nicely the Blackberry. This can be left floating at the surface on a line and towed around. If you hear any boat traffic you just tension the line and submerge the conainer temporarily.
My dive computer is a Suunto Vyper so all you have to do is either sync the times between the GPS and the computer or just note exactly the time-difference in seconds, and the Vyper allows you to mark points on the dive profile (PLAN button) during the dive. So after the dive it's a very easy matter to sync the profile against the GPS location using a timescale.

 

[miketsp]

I'm sorry, I don't get the need, unless you're using a DPV. Otherwise scuba diving doesn't involve swimming great distances.

If you use GPS on the surface to locate your starting point, you can use traditional UW navigation (course and speed & time) techniques to track movement from that point. With decent skill you should be able to know where you are within the same margin of error as handheld GPS units afford.

Most of the time the GPS chip in my Blackberry gives me +/- 3m accuracy.

On a 1 hour dive I really don't see how you're going to come anywhere near that with dead reckoning. If there's any sort of current it would be impossible.