Underwater "GPS" or location tracking - is it possible?

I'm trying to figure out a way to navigate a submersible under water (from 30-150m depth) and I'm pretty sure GPS will not function in this situation unless there was some kind of repeater with antenna underwater transmitting data (which has lots of other implications as well & lots of repeaters would be needed).

Having EXACT coordinates underwater isn't necessary but being able to navigate in a fairly accurate direction would be extremely beneficial. Also surfacing (or maybe 1 meter below surface would be better) to get a reading would be possible as well as the vessel knowing the GPS location at the beginning of the journey, so it will know the starting point.

The vessel will be able to accurately track its travel speed, pitch, depth, etc as well as it's magnetic compass reading (or any other form of compass reading that is possible in a submerged vessel). I would think with these things the vessel could get a very close approximation of it's location using the data from speed, pitch/angle of travel, depth and heading - though IDK how to compensate for the speed of water (such as rivers w/n the ocean, sea, lake, etc like gulf stream flows).

I'm trying to find the best method for this that doesn't cost $30-50K (or more) and can navigate as long as the vessel can stay submerged (20-40 hours at 5-10 knots or 5.75 -11.5 mph for 115-460 miles).

Is there a way to determine water speed relative to a moving vessel.

If a starting a map were input into a computer and the starting point (GPS) was entered as well as the destination, I would think a course could be determined by a compass reading and then a display could show if you are on course or if you should steer R or L to maintain the course heading. Maybe every 1/4 or 1/3 of the way to destination, the vessel could surface (or even send small buoy) a few meters to surface, to get a GPS reading to ensure calculations are working correctly.

Anyone have any insight into a project such as this or ideas on how it might be possible?

PS - I'm not interested in military applications for guiding their subs, the new "underwater GPS" they are developing. I don't care about that as it isn't going to be accessible to civilians any times soon and it would be way too expensive, so don't post about that.

a reply to: DigginFoTroof
The biggest question which I don't recall seeing in your project is fresh or salt water? If you know how to read engineering graphs, this picture is worth a thousand words by showing two different curves for how much electromagnetic signal is lost per meter in salt water (top line) versus a specific body of fresh water (bottom line).

Underwater Radio


The GPS frequencies are off the right hand side of the chart, like way off the chart. So GPS signals don't do well underwater, and even the lower frequency example shown of 1.8 MHz doesn't fare will in seawater.

What the chart shows is that lower frequencies fare better, but some of these frequencies may not be readily available for a number of reasons. Even if you could use those frequencies, the other problem you could run into is that lower frequencies can't carry as much information so to use them in some kind of homemade GPS might mean getting very low quality signals that won't give much accuracy.

If you can get a fix on your original position at the surface using regular GPS, you should be interested in how other subs navigate without using any underwater GPS, they use a inertial navigation systems which incorporate a gyroscope, accelerometer, and a computer. RLGN is replacing ESGN.

web.archive.org...
"ESGN (Electrostatic Gyroscopic Navigation)
operates in a near perfect vacuum
rotor is solely supported by an electrostatic field
essentially frictionless
resets only required once every 30 days
Wearing out and failures are increasing, so being replaced by RLGN

RLGN (Ring Laser Gyroscopic Navigation)
Operates without moving parts
Two (or more) lasers travel around object
As ship moves, laser takes slightly more time to travel
Time delay causes a phase difference that is used to calculate movement"

I have no idea how much they cost, but they don't sound cheap.

If there are features on the bottom, and the sub can ping those, it can navigate by those features but it's not too accurate.

If you happen to figure out a way to do it, don't tell anyone and go get a patent as quickly as you can. You, and the next 10 generations of your family, will live very comfortably forever more!

Navies around the world have been trying to figure this out for nearly a century. Communications underwater with anything other than sound (i.e. sonar, etc) has proven quite the challenge!

In fact, one of the things they were studying with HAARP was long distance ULF submerged communications. One of the bigger problems is, the lower the frequency, the lower the bandwidth, hence lower communication rates. Navigation takes a fair amount of data, and at ULF rates the data would be obsolete by the time it was fully transmitted / received.

a reply to: DigginFoTroof
Airplanes navigate with a VOR (Very High Frequency (VHF) Omni-Directional Range) and when they tune into the channels of the different locations, they are able to pinpoint where they are on a map. It would be interesting if they can set up a similar system under water that give's location and depth.

a reply to: Alchemst7

If they could, they would have a long time ago.

Undersea, in some respects, is even more challenging than space (not all, but some).

Submarines use a very good inertia navigation system or INS.

Research civilian subs..........

a reply to: DigginFoTroof

Drag a floating buoy around maybe?

Afaik military subs use communication buoys to avoid surfacing.

a reply to: DigginFoTroof

New to the sub business I guess lol. Interesting hobby for sure.

If I were you I'd look into high precision accelerometers and gyros and stuff..
Oh well best of luck!

-Driver