Definition
The distance run comes from the ship's log, a paddlewheel, impeller or electromagnetic sensor measuring speed through the water and integrating it to a totalising distance. Log readings should be recorded at every fix, course change and watch change so any interval can be reconstructed. Impeller logs foul quickly with weed and growth and under-read progressively, so the log should be calibrated against a measured distance run in both directions to cancel tidal effect.
Want to apply this on the water?
Ask Saily out loud for an example, a scenario or a simpler explanation.
Talk to Saily