Germans used another method for calculating very exact ranges in WW2, partly because their UZOs -unlike what SH3 wrongly shows- had no stadimeter or graded reticles. It is more complicated, but if you dominate using a wiz-wheel like the one I did, it is quite easy: Get target speed and course by steering paralell or calculating differences while overtaking the convoy (Or get it from BDU if the contac report is detailed enough). Now, knowing AOB and speed you just need to observe the change in bearing of the enemy over a period of time. Say you want to use the easy 3.15 minutes rule...you note the bearing to target, start the cronometer and wait 3 minutes and 15 seconds. Then you stop it and note the new bearing to the target. Say it changed 20 degrees to backbord....now all there is left to do is setup your wiz-wheel to show the solution, more or less like this:
A target moving at 8 knots covers 4.11 metres per second. In 3 minutes and 15 seconds it covers 802 metres (So you can convert quickly 8 to 800 with the 3.15 rule). You have now the first side of your triangle. The original AOB was 70º, and the target changed 20 degrees bearing. Those are two angles in the triangle, and because all of them must be together 180º, we know that the other angle is 90º. Align your sine scale in the wiz-wheel so that 70º is opposite the 800 (or 8000) in the range wheel . Now, opposite the 20º you see 2900. That's the range to target when we started our chronometer. Align now the 800 with the 90º angle (Which is also the AOB at the moment to stopping our chronometer) and read opposite the 20º 2700. That's the current range to target :up:
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