How do submarines navigate under water?

Question

I don't understand how submarines navigate over long distances, under water. You cannot see, so a map is no good. GPS would not work under water. Sonar would only work if you had a 3D map of the whole sea bed. A compass and timing would be too inaccurate. Perhaps some kind of inertial reference system using gyroscopes?

Answer 1

Light does not penetrate very far into the ocean, so submarines must navigate through the water virtually blind. However, submarines are equipped with navigational charts and sophisticated navigational equipment. When on the surface, a sophisticated global positioning system (GPS) accurately determines latitude and longitude, but this system cannot work when the submarine is submerged. Underwater, the submarine uses inertial guidance systems (electric, mechanical) that keep track of the ship's motion from a fixed starting point by using gyroscopes. The inertial guidance systems are accurate to 150 hours of operation and must be realigned by other surface-dependent navigational systems (GPS, radio, radar, satellite). With these systems onboard, a submarine can be accurately navigated and be within a hundred feet of its intended course To locate a target, a submarine uses active and passive SONAR (sound navigation and ranging). Active sonar emits pulses of sound waves that travel through the water, reflect off the target and return to the ship. By knowing the speed of sound in water and the time for the sound wave to travel to the target and back, the computers can quickly calculate distance between the submarine and the target. Whales, dolphins and bats use the same technique for locating prey (echolocation). Passive sonar involves listening to sounds generated by the target. Sonar systems can also be used to realign inertial navigation systems by identifying known ocean floor features

Answer 2

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RE:
How do submarines navigate under water?
I don't understand how submarines navigate over long distances, under water. You cannot see, so a map is no good. GPS would not work under water. Sonar would only work if you had a 3D map of the whole sea bed. A compass and timing would be too inaccurate. Perhaps some kind of inertial reference...

Answer 3

Subs do have such charts that give the depth and contours of the bottom and also use inertial navigation systems. I not sure exactly how the inertial system works but I do know they have them and when all else fails you could us the GPS system by extending the antenna shallow enough to get a signal. When that fails you can take star and sun sights with the periscope.

Answer 4

They DO have 3D maps of the seabed, these days...But, much of the time, they're in deep, open water, so there's not much in the way.

As you suggest, much use is made of inertial navigation, with position updates from underwater beacons, known marks, etc, as well as occasional spot-checks from space- and ship-borne references.

Back in the good old days, it was all down to very good navigation...

Answer 5

This is as much a question as an answer - don't subs often 'float' antenna packs to the surface for better/improved communications. I'm talking like 100' of cable with a small buoy with antennas.

If they do, which I think they do, couldn't they have a GPS antenna up there like I have in my car (external antenna) so that they could, at least periodically, get a better fix on their location?

Not knocking any previous answers, but wondering aloud if they do this as well.

Answer 6

Sonar would still give them the bottom and depths and things nesr them. A compass still works to pick a course. Charts show depths so a course can be planned. Some small subs have underwater cameras to see up front or where ever they are pointed. There is some light.Knowing there speed and the time would be very important to determine where they were.

Answer 7

Inertial navigation

Answer 8

I kknow this isn't strictly an answer but i'd just like to say what a good question and what an excellent answer from Marshall Lee

Answer 9

Radar? Last time I checked radio signals don't work too well underwater. There are morons afoot.

Answer 10

Im not sure what the exact term for it is but it's just like echo-sounding boats use it too.
It sends out a signal/sound and the vibrations from the sound bounce off things in the sea bed or just in the sea, those vibrations create a sort of 3D map. Dolphins and whale's use it thats why they make those weird sounds!