Underwater GPS

[archman]

"Chinese scientists have developed the first high precision underwater global positioning system (GPS). Tests have shown the new system can detect horizontal position within 5cm and depth precision within 30cm."

This is a joke, right? Last I heard there was no chinese GPS constellation in orbit. And the reported accuracy here is simply ludicrous. Even using WAAS, you're not likely to get better than 9 foot accuracy... that would be something like three HUNDRED centimeters.

This supposed chinese system requires four floating GPS receivers/transitters I suppose for triangulation, and the sonar system would be used to get precise depth values. I'm assuming the four floating buoys are fixed sites hooked hooked into something like a WAAS network in order to achieve this absurd 30cm accuracy.

 

[Bubble Blower 479]

You're right that the Garmin waterproofing is very limited and all the data ports must be closed. I was not suggesting anything but tracing the location of the float on the surface. Of course this could only be done in a calm lake environment and I would still want added protection like a ziplock bag or something. My biggest fear would be the guy on the Jet Ski that decided he wanted my GPS and borrowed it on the no return plan. It's great to use on a boat when you want to return to a specific location. We also use them to ice fish when we find a good location. I have seen excellent fishing locations vary by only a few yards. Just as a side note, I have had an estimated accuracy as low as 6 feet under the right conditions. We have 2 Rino 120's and use them constantly. The Rino will transmit your position to the other unit and my son and I play Hide-n-seek up in the mountains.

 

[IceFrog]

This is a joke, right? Last I heard there was no chinese GPS constellation in orbit. And the reported accuracy here is simply ludicrous. Even using WAAS, you're not likely to get better than 9 foot accuracy... that would be something like three HUNDRED centimeters.

This supposed chinese system requires four floating GPS receivers/transitters I suppose for triangulation, and the sonar system would be used to get precise depth values. I'm assuming the four floating buoys are fixed sites hooked hooked into something like a WAAS network in order to achieve this absurd 30cm accuracy.

Here's a link to a similar system that claims similar results but goes into a bit more detail on how the system operates. It describes the system using DGPS from a shore station with an accuracy of +/- 10 metres to +/- 1 metre depending on the shore station used. The underwater portion of this is described as follows: "The timing resolution of the time of arrival of an acoustic signal is of 0.5 10-5 second, the accuracy is close to 10-4 second when working at 30 Khz, that means +/- 15 centimeters. Same accuracy is achieved using spread spectrum signals."

The chinese system must be identical or very similar.

Regards

 

[darkmoon3d]

I found this site a while back. A bit pricy but and not sure if it uses gps or not; but it allows for underwater measurements and modeling very precisly.

Can't wait until this product becomes cheaper for consumer rather than profesional use...

Here's a link to a similar system that claims similar results but goes into a bit more detail on how the system operates. It describes the system using DGPS from a shore station with an accuracy of +/- 10 metres to +/- 1 metre depending on the shore station used. The underwater portion of this is described as follows: "The timing resolution of the time of arrival of an acoustic signal is of 0.5 10-5 second, the accuracy is close to 10-4 second when working at 30 Khz, that means +/- 15 centimeters. Same accuracy is achieved using spread spectrum signals."

The chinese system must be identical or very similar.

Regards

 

[archman]

Here's a link to a similar system that claims similar results but goes into a bit more detail on how the system operates.

That's a neat website. It gets over my head in some places. As for affordability, well besides the handheld unit there's the infrastructure cost of the shore and and buoy transmitters to factor in. I don't see this becoming an option really anywhere within the next ten years, 'specially with the reductions being planned in NOAA's budget (to help pay for NASA of course).

 

[IceFrog]

Unfortunately for most divers the only affordable option for probably quite a while would be carrying a handheld GPS with them in a waterproof box and either send it to the surface on a towline, or carry it on their dive flag to mark where they travelled underwater.

You can also try this link for an underwater unit. for the military. I have yet to see a civilian version of this unit though. I can say though that the unit is just waterproof and probably does not work underwater (as in aquire GPS Signals).

Regards

 

[pearcey]

i have a compass, call me old fashioned but i have never been lost.
if you really want to mark a wreck for example why not use a rope and bouy, and then calculate your gps whilst sipping cup a soup on the boat

 

[IceFrog]

i have a compass, call me old fashioned but i have never been lost.
if you really want to mark a wreck for example why not use a rope and bouy, and then calculate your gps whilst sipping cup a soup on the boat

There's no reason you couldn't do this. The GPS just allows you to record a large number of locations within it's memory. (Mine has the ability to store 1000 points - although I haven't even come close).

A number of people like to know where they are while underwater. Although none of the GPS units work underwater, there are a few methods.

Regards

 

[got4boyz]

http://www.longbeachdive.com/scubanav-detail.htm

Has anyone heard of or used this Scuba-Nav? I came across the website doing a search for dive flag floats. Sounds interesting and I'd like to try it, but kind of pricey without knowing how well it really works and how easy/difficult it is to use.

Any thoughts would be appreciated.

Thanks

 

[got4boyz]

Even if you have never used or heard of the Scuba-Nav before I'd be interested in hearing your opinion of it.

Basically, this is how it works.

The Scuba-Nav has a remote GPS antenna which is mounted to a dive flag float. The antenna has a 55 ft cable which is an attached to a GPS unit in a waterproof housing. The GPS satellite signals are sent through the antenna to the GPS reciever that the diver carries underwater. This allows the diver to know where he is underwater.

I haven't done a lot of shore diving but want to do more and thought this would be a great way to get back to where I started from! Or to navigate out to someplace I wanted to go, like a wreck or something. Many have already been given GPS coordinates that you can program into your GPS and then use it to get there with.

Anyway, I'm interested in what others think of this.