Längskoordinate

Längskoordinate, or longitudinal coordinate, is the angular distance of a point east or west of the prime meridian on the Earth’s surface. It is a fundamental component of the geographic coordinate system used to specify a location in combination with latitude.

Measurement and range: Längskoordinaten are typically expressed in degrees, minutes, and seconds or in decimal degrees. The standard range is -180° to +180°, where positive values indicate positions east of the prime meridian and negative values indicate positions west. Some systems use a 0–360° convention with 0° at the prime meridian.

Reference and geometry: All lines of longitude, or meridians, are half great circles that run from the North Pole to the South Pole. They converge at the poles and are longest at the equator. The prime meridian, defined to pass through Greenwich, England, serves as the 0° longitude reference.

Relationship to latitude and datums: A point on the Earth is specified by a pair: latitude (north–south) and longitude (east–west). The exact longitude value for a point depends on the chosen geodetic datum, which defines the shape of the Earth and the reference frame. Common datums include WGS84 (used by GPS) and NAD83 or ETRS89 in regional contexts.

Applications: Längskoordinate is central to navigation, mapping, GIS, GPS, and geotagging. It enables location-based services, route planning, and spatial analysis. decimal degrees are frequently used in digital systems for simplicity, while degrees, minutes, and seconds remain common in traditional maps.

In Swedish usage, längskoordinate is typically paired with latitud, and together they locate any point on the globe within a chosen datum.