[THEBERBSTER]

How To Calculate A Targets Speed By Using The Periscope Cross Hairs.

Count the number of Seconds it takes for the > Targets Bow and Stern to pass across the > Periscope Cross Hair.
Time taken = metres per second.
Multiply the number of seconds taken by 3,600 (number of seconds in an hour)
Divide the total by 1.85 (To convert KPH to Knots)

Length of the Target is needed from the Recognition Manual.

Target > Small Passenger Type Merchant 1,719 tonnes.
Length > 80.0 metres.
Number of seconds taken > 25.
Length 80.0 divided by 25 seconds = 3.20 metres per second.
3.20 metres per second x 3,600 seconds in an hour = 11,520 metres/1000 = (11.52km).
11,52km divide by 1.85 to convert Kilometres Per Hour (KPH) to Knots = 6.22, or 6 knots.
Target is traveling at approximately 6 knots.