Assuming you use metric measurements, distance covered in hundreds of meters = speed in knots if you time it for 3 minutes 15 seconds. I never bothered to figure out the time frame for Imperial measurements but it should be easy enough with a calculator.
1 nautical mile=1852 meters, and I think I'll go with this since SH4 is based around metric units with a built in converter to Imperial measurments. Assume a target is going exactly 9 knots, and you want to calculate the interval
t where the distance covered in
t time equals 900 yards.
9 knots = 16668 meters per hour.
1 hour = 60 minutes.
Therefore, 9 knots = 277.8 meters per minute.
1 yard = 0.9144 meters.
Therefore, 277.8 meters per minute = 303.8 yards per minute.
900/303.8 = 2.96 minutes, or 2 minutes 58 seconds to cover 300 yards.
Mark point on map, start stopwatch. Mark point again 2 minutes 58 seconds later. Measure distance between points. Distance covered in hundreds of yards is speed in knots.
This is, of course, assuming my math is correct.
