How submarines navigate and find targets: 2-minute tech 

During WW1 they had to surface to charge the batteries and then the Sailors would use a Sextant and pocket watch/wrist watch and a Chronometer just like the days of sail and in the US we still train our Sailors to use them in case of Emergencies or if they have to Abandon Ship into a life raft, I should imagine that British Sailors would have to do the same

@@kevnwarriner8819 ah that makes sense. Very interesting, thank you 👍

Agree. They mention INS in same breath as 'hyper accurate charts'.

No stories Dan, he’ll just say it’s all classified 😉

so basically a moving Sonobuoy. Question is how would the UUV relay back information to the sub without both resurfacing. Wire guided works but I'm not sure a 2-way acoustic relay would. I know they have acoustic guided torpedos but I think that's more basic form.

Not just enemies and fifth columnists. One CME, and it's all over. The last one was in 1947. So, it didn't matter much. We didn't have satellites or gps, though it did affect radio/phone communications around the world. If it happened now however, there'd be chaos.

Is the earth's gravity field not accurately charted?

@@Naval-Gazing The horizontal component of the Earth's gravitational field is not generally available to high precision, nor is it stable with time. In order to chart it, an ultra accurate inertial frame of reference is required. The first device capable of achieving such accuracy was the electrostatic gyroscope developed by the Charles Stark Draper Laboratory. Inertial navigators are unstable, they accumulate significant positional errors with time, a way of bounding these errors is by position fixes, but GPS is only available if the submarine surfaces. The UK, USA and others no doubt, have specialized survey ships that are capable of surveying the horizontal component of the gravitational field. I suspect this is what they mean by 'very accurate charts'. The map of the Earth's horizontal component of the gravity field is analogous to the height of terrain and can be used in exactly the same manner as the terrain contour matching navigation system in cruise missiles to bound the accumulated errors of the inertial navigator. A submarine, or surface ship, fitted with such a system only needs one initial position fix to initiate accurate inertial navigation without any need for GPS, so long as it stays within the corridors that have been surveyed.

@@glynnwright1699 Thank you for all that information --- the final paragraph, in particular. Would I be correct in assuming that the measurement that you described could be combined with sonar scanned topography and magnetic field measurements? Or would mapping the horizontal component be sufficient?

@@Naval-Gazing You are correct that inertial navigators can, and do, use other positional information to improve their accuracy. The benefit of the gravity field is that it can't be jammed and it can be measured passively, without radiating any energy that might be detected by an enemy. An inertial navigator can produce very accurate results with only occasional position fixes. There are other 'tricks' that can be used, for example, if the vessel changes direction, the manner in which the inertial navigator position errors accumulate afterwards can be used to determine the origin of the errors in the sensors and their magnitude, so that the whole system can be 'tuned' to have a higher short term performance.

@@glynnwright1699 Fascinating --- especially the calibration process. That all makes sense, and thanks for taking the time.

It was basically designed around letting tourists view something themselves, trying to do so as cheaply as possible, and hubris to ignore the warnings of people with more expertise.

The deeper you go, the more they like it.

@@megafauna8374 Well thats just not the case.. They prefer wider, larger girth to depth capability...

They spent most of their time above the surface as they were all diesel/electrics. They would only submerge when they were avoiding enemy ships or closing in to attack. The American submarines had a very sophisticated gyroscope and mechanical computer. I would imagine the Germans and British had a similar system as well but it was limited.

It isn't a subject govts want people to have a very big discussion about.

It's 'two minute tech'.

Thats dam pricey, you guys will get something that beats anything China has but I dont think Aus will be getting this, a mix of UK and UK tech