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Actual Depth

Get accurate depths on your map instead of broad ranges.

The thumbnail shows it in action - it just exposes the actual depth at the cursor position on the map UI.

The larger images are of actual 1943-1945 Kriegsmarine charts, from https://maps.nls.uk/coasts/german-naval-charts.html, or overlaid on a modern map at https://maps.nls.uk/geo/find/#&layers=117.

The top right inset chart shows the entire North Sea. The chart to the left of that is a detail chart that is limited to the small area off the coast of Dover. From that chart I have finally clipped just the minimal rectangle capturing both Dover and Calais.

Observe just how many soundings are indicated on the map.

The colored image shows how far each position is from the nearest sounding or depth contour on the historical chart to help demonstrate how little uncertainty there would be for your depth at a given position. Green is within 300 meters, light blue is within 600, dark blue is within 900, and purple is within 1200. To put that into perspective, those bands represent just 3.5, 8, 12.5, or 17 boat lengths away for a VIIC (e.g. 300 - 67 = 233 first subtracting your own boat's length, then 233/67 = 3.5 boat lengths away).

No commander was limited to "gee, somewhere between 20 and 50 meters, idk" that the game provides. Even in the dark blue or purple regions you'd still be interpolating between two known depths -- the biggest difference I could spot between two 'adjacent' soundings was just east of the Varne, going from 27 to 49 meters, a 22 meter change over 1.4 km. Generally, adjacent soundings differ by just 3-8 meters, so your uncertainty about the depth at a spot between them would be about +- 2 meters.

Yes, soundings get dramatically less frequent the farther you get from coasts, but everywhere within a U-boat's crush depth seems to have been known to about the same level of detail as what I show here. Sure, in the middle of the Atlantic you'd only have a broad range and wouldn't know that one spot was 4713 meters while another was 4724, but it's not like exposing the true number makes any difference since you won't be diving to even 5% of that depth.

Given the choice between the extremely broad depth ranges and the precise number, I think the latter is much closer to historical reality than the game's choice.

This is user error. Soundings give the distance between the keel of the boat and the seabed, which depends on the model of boat, your depth, and even how heavy the seas are if you're surfaced. The most confusing element here is the UI depth gauge, which displays '0m' when surfaced instead of displaying around 5 meters, as the actual instruments in the control room do, and that ordered depths don't use the keel depth. If you order a dive to the actual seabed depth, you will bash your keel into the ground when your depth gauge reads about 5 meters above that depth, because your boat is not 0 meters tall. Fixing this would require patching the depth UI gauge to behave differently. None of these issues involve any error in this mod, which simply reports the true number of meters of water measured from the seabed to a calm surface.