Hi Nico,

This sound a bit like the software for the speed indicator on my boat. I used a look-up table to convert the time between 2 pulses from the log (1 pulse every 18.52 meters) into knots. Obviously, at very low speeds, the table has to be enormous, but you can always set a limit (e.g. below 0.5kt always display 0). If a human has to handle the results, update the display at about 2 Hz.

Good luck,

Richard