The only reason I check the ID manual is to confirm target drafts so that I can slip magnetic torpedoes under their hull, particularly escorts.
If you don't have map updates on, the 3:15 rule is harder to use to obtain ship speed.
In which case if you really need to know the ship speed you will need the target length to use the Fixed Wire method of speed calculation.
I'm running 100% realism with map contacts off also. I usually estimate the speed unless it is a convoy radio contact where speed was provided.
Steve
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