Underwater GPS

[ba_hiker]

Navy uses inertial navigation for subs. Dos not even require working surface stations. Expensive, but getting cheaper and smaller...

 

[archman]

Inertial navigation accuracy degrades with length of use. Submarines prefer to surface when they can to get satellite fixes to "re-calibrate" their INS, especially when operating in confined waters.

At least that's what I learned from Tom Clancy...

 

[Don Burke]

Inertial navigation accuracy degrades with length of use. Submarines prefer to surface when they can to get satellite fixes to "re-calibrate" their INS, especially when operating in confined waters.

At least that's what I learned from Tom Clancy...

I've worked with various systems on various submarines.

We would take external fixes to compute reset parameters and actually perform resets as needed to meet whatever mission goals we were after.

The systems are subject to disturbance from variious sources including gravitational anomalies, power, temperature, bum inputs, and physical shock to the system. The newer ones are better, not perfect.

A submarine doesn't need to surface to get a satellite fix. As long as an antenna can be raised above the surface, the boat can stay at periscope depth. The exposure to RADAR involved is not a minor consideration.

I made Polaris patrols in the days before GPS and we would track LORAN for months at a time with checks against other systems from time to time. LORAN is pretty good within it's limitations. TRANSIT was fun to operate, but I don't miss it at all since it exposed the boat too much. The early days of precision bathymetric navigation were pretty neat too.

When I got on a boat with GPS, I thought I'd died and gone to heaven. Not only is there position available virtually constantly, but satellite reference velocities are available for damping for the whole time the receiver is locked on.

 

[BigJetDriver]

All,

The problem is simple. All we need is a Ring Laser Gyro for IRS (Inertial Reference System) input, and a GPS (Global Positioning System) to update it when we do surface. The B-777 has three of these systems linked in a "voting logic" set-up. This is why we can be over a thousand miles out in the South Pacific and look down to see an aircraft directly below us, and another one directly above us. (Doesn't happen that way often, but it does happen!)

Now, what we need is some genius to shrink one of these systems, reduce the power requirements to battery power, AND make it affordable to divers! (It would take a genius!!) Any takers???

Cheers!! BJD :anakinpod

 

[archman]

Now, what we need is some genius to shrink one of these systems, reduce the power requirements to battery power, AND make it affordable to divers!

I'm free on Sunday.

 

[DoUDive2]

I'm free on Sunday.

That made me chuckle. So I posted my response in the "Scuba Humor" subforum, which is under the forum on "Non-Diving Related Stuff."

 

[red dwarf]

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

lots of probs in this regard due to the nature of the GPS that the USA let us use
the power of the signal is one prob, the signal is very low power at a high freq. this is not what you need underwater ULF is better not 1200 odd Mhz

 

[archman]

You're gonna get an awful low transfer rate using ULF. You'd probably have to sit tight for an hour or so in order to tag your position. It was my understanding that the Navy only sent ULF messages saying "come to the surface so we can use higher frequencies". Or maybe that's ELF, or HOBBIT maybe.

 

[Don Burke]

You're gonna get an awful low transfer rate using ULF. You'd probably have to sit tight for an hour or so in order to tag your position. It was my understanding that the Navy only sent ULF messages saying "come to the surface so we can use higher frequencies". Or maybe that's ELF, or HOBBIT maybe.

ELF is a very low data rate business. I seem to recall only a few characters per minute and the transmitter power being obscene. The plan was for war orders and such to be sent when nothing else worked.

For a SCUBA nav system, I like the one where buoys with GPS receivers compute the diver's position from some sort of transponder system and send it to the diver's set on an acoustic link. You can make something like that work with two buoys, although I'd prefer three stations to eliminate ambiguity.

 

[archman]

For a SCUBA nav system, I like the one where buoys with GPS receivers compute the diver's position from some sort of transponder system and send it to the diver's set on an acoustic link. You can make something like that work with two buoys, although I'd prefer three stations to eliminate ambiguity.

That's what I like too. In the slightly fanciful future I can maybe predict smaller sanctuaries ponying up for moored buoys, and local dive shops selling/renting the acoustic handheld unit. With miniaturiation of GPS ongoing, it may even be affordable to purchase small tethered buoys yourself... it's the acoustic hardware that'll likely be the pricey part.