[Heibges]

Matching speed method is good up to 17 knots depending on the top speed of your uboat. For sure, you only want to use this on the surface because you will really deplete your batteries trying to use it submerged at flank speed.

MILS method useful at all AOB's not just perpendicular. You need columns in your range chart for each AOB. I just have so much subsim experience that I always end up in the perpendicular position so I have never bothered.

For example.

A ship that measures 10mils 90°, would only measure 6mils at 45° AOB.

To give a modern example, a T-72 Soviet MBT is about 2.5 mils at 2000m perpendicular, but about 1.7 mils at 2000m at a 45° angle.

This shows how SH3 is very realistic. Another reason why uboat tonnage was reduced as the Uboats were forced below the surface is that it is much easier to collect fire control data (speed, range, and AOB) surfaced than when you are submerged.

It is much easier and more precise to spend an hour on the surface getting the speed through matching speed as opposed to the 3.15 minute method. In heavy seas and/or fog you might not have much more than 3 minutes of total visibility.