Common Log

A common log, also sometimes referred to as a ship log, speed log or chip log, is an instrument which is used to measure a ship’s speed and the distance it has traveled. The speed is determined by referencing the water flowing past the hull (water reference speed) or by the seabed (ground reference speed).

There are five different types of common log which all work on different principles: the electromagnetic common log, the pitometer common log, the doppler common log, the impeller common log and the satellite common log. See their individual glossary entries for more information on each.