A lubber line, also known as a lubber's line, is a fixed line on a

compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with ...

binnacle A binnacle is a waist-high case or stand on the deck of a ship, generally mounted in front of the helmsman, in which navigational instruments are placed for easy and quick reference as well as to protect the delicate instruments. Its traditional p ...

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

plan position indicator A plan position indicator (PPI) is a type of radar display that represents the radar antenna in the center of the display, with the distance from it and height above ground drawn as concentric circles. As the radar antenna rotates, a radial tra ...

display pointing towards the front of the ship or aircraft and corresponding to the craft's centerline (being the customary direction of movement). The line represents 0

degree Degree may refer to: As a unit of measurement * Degree (angle), a unit of angle measurement ** Degree of geographical latitude ** Degree of geographical longitude * Degree symbol (°), a notation used in science, engineering, and mathematics ...

s and is therefore the zero-point from which relative bearings are measured, e.g., "''twenty degrees to

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Ham ...

''". Compasses on sailboats may have additional lubber lines at forty-five degrees from the centerline. This represents about as close to the wind as the average boat will sail. These lubber lines may be used when sailing

close hauled A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface. The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. ...

to see if you are on the closest course to your destination, without having to add or subtract the 45 degrees every few minutes, or recalculate your required heading every time you tack. The main line on the compass reads your current (close-hauled) heading and the leeward lubber line will read the bearing to your destination, regardless of whether you are on port or starboard tack. Lubber lines also help you to see windshifts when racing. If you are sailing close-hauled with good trim and you notice that your bearing to the windward mark starts to drift outside the lubber line (angle becoming greater than 45 degrees) you are being headed, and should consider tacking. Directional Gyros on aircraft also have additional forty-five degree lubber lines. These are useful for intercepting tracks and making procedure turns.

Etymology

The name comes from "lubber", a nautical term for a novice sailor or

landlubber In English-speaking popular culture, the modern pirate stereotype owes its attributes mostly to the imagined tradition of the 18th century Caribbean pirate sailing off the Spanish Main and to such celebrated 20th century depictions as Cap ...

. It has also been called a lubber's mark or lubber's point, though use of these terms declined in the 20th century.

References

Navigation Navigational equipment Radar {{geo-term-stub