Running miles
As miles running in is Nautical that with a timing controlled traveling through a test route referred to from the rotational speed of the drive and propeller to be able to derive the airspeed of the vessel.
The measuring line is exactly 1 nautical mile long (hence the name) or a multiple thereof. Usually their beginning and end are marked by landmarks or special beacons ("mile beacons ") that must be passed on a certain course . The time is stopped and the exact speed over the ground is determined.
The comparison with the built-in log or the tow log ( patent log ) allows this airspeed indicator to be calibrated, but the exact result of the mile run also depends on the draft of the ship, the possible ocean current and the nature of the underwater hull (mussels and other vegetation ).