[don1reed]

The easiest way to "do speed" is to be setting off the target's track about 1000m, either travelling at 1 kn. or temporarily at all-stop.

Place the vertical reticule on the targets bow, begin the stop watch...without moving the scope until the target passes, stop the stopwatch when the stern crosses the vertical...do the math, i.e.,
C3 (150m LOA) / time in seconds x 1.95 = speed in knots.

Distance: never worry about the distance...just get close enough to the target's track to where the length of the ship fills the scope lens at X6 or X10 (depending on the mod you use.)