[Aufklarer]

A simple speed calculation is:

1. Identifying the ship, if you have the enhanced recognition manual mod it will give you the ships length in meters.

2. Measure the time it takes the ship to completely travel the length of the crosshair in your periscope (the vertical graticule).

3. Use the following equation: Length/Time x 1.94 = speed in knots

This method only works when at a complete standstill and the periscope isnt moved during the timing process. If you require a speed calculation on the move i suggest the Time-Distance-Speed equation. For that though you will need to know range in order to calculate the true course of the target.

If i am not mistaken there are also pre made authentic speed calculation grids that were used in the actual war to speed up the process, these are actually modded into the game (i forget exactly who, but i have them). That would negate the requirement for you to use a spreadsheet.