Speed Log

In maritime terminology, a speed log, also sometimes referred to as a ship log, common 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 speed log which all work on different principles: the electromagnetic speed log, the pitometer speed log, the doppler speed log, the impeller speed log and the satellite speed log. See their individual glossary entries for more information on each.