Glossary Archive

Navigational lines drawn on a chart, each representing a possible location of a vessel based on a single observation or measurement.  A line of position (LOP) is a fundamental concept in marine navigation used to determine a vessel's location. It is a line on a nautical chart along which a ship is known to be...

A vessel loses way when she slows down and stops in the water

The lowest level that sea tides can reach under normal meteorological conditions, based on astronomical influences such as the gravitational pull of the moon and sun. Lowest Astronomical Tide (LAT) is a tidal datum used as a reference point for charting and navigation. It represents the lowest predicted tide level that can occur due to...

The marker in the compass which is aligned with the fore-and-aft line of the boat against which the course can be read off on the compass card

The leading edge, which is the part of the sail that faces the wind when the sail is set correctly. The luff of a sail is a critical part of sailboat dynamics and sail trim. It is the forward-most edge of the sail, running from the head (top) of the sail down to the tack...

To steer a sailing vessel closer to the wind, reducing the angle between the boat's heading and the direction of the wind.  "Luff up" is a critical manoeuvre in sailing that involves steering the boat closer to the direction from which the wind is blowing, known as "heading up." This action reduces the angle between...

A temporary drop in wind speed

Magnetic North refers to the direction indicated by a magnetic compass, which points towards the Earth’s magnetic north pole. This differs from True North, the direction towards the geographic North Pole. The difference between Magnetic North and True North is known as variation (or magnetic declination) and varies depending on the location on Earth. Navigational...

A UK government agency responsible for investigating marine accidents and incidents to improve maritime safety. Part of the Department for Transport, the MAIB examines incidents involving UK vessels anywhere in the world and foreign vessels in UK waters. Key Roles and Responsibilities of the MAIB Investigation of Marine Accidents: The MAIB investigates accidents involving all...

To hoist the sails and get under way