[JScones]

Originally Posted by GoldenRivet

Americans had a thermalgraph (at least i think thats the name) if im not mistaken, it would measure the outside water temperature and when there was a sudden and rapid change in temperature they knew they were passing a thermal layer.

Bathythermograph. They appeared en masse in US subs from around the beginning of 1943.

Technology on German U-boats was a smidge more primitive and certainly less accurate - they drew water into the boat and measured it with Mr Thermometer, most likely when checking salt content. In fact some sources say that the Salinometer also measured temperature. For example, from U-490 interrogation report:

(E) Salinometer:

An instrument for measuring the salt content of water was in the control room. It was described as a graduated glass tube, about 12 inches in length and tapering toward the top. It was weighted with lead shot and floated in a metal cylinder which had connection with the outside seawater. Some prisoners believed that this instrument could indicate water temperature and density as well as salt content.

Check out Jürgen Oesten's video interview with the devs where he talks about thermal layers and detection (or lack thereof) of same.

Originally Posted by GoldenRivet

also you should be aware that SH3 Commander adjusts the thermal layer globally not locally. in other words... in real life the position and depth of the thermal layer varies from place to place around the world... in SH3 Commander it makes it the same depth for all over the planet.

Gotta love SH3 limitations.

Actually, when I'm stationed in the Nth Atlantic I remove the first two sets of figures for the simple reason that thermoclines tend not to occur in the Nth Atlantic until well below 200 metres, which is outside normal U-boat diving depth (the only reason I don't remove the third set is that if I did I might as well remove all sets as U-boats tended not to regularly dive below 220 metres. )

I only add them back when I'm in the Med or Indian/Pacific.