lengtegraden

Lengtegraden are the angular units used to describe a point’s east–west position on the Earth’s surface, expressed as degrees of longitude. The prime meridian, defined at 0°, runs through Greenwich, and longitudes are measured east or west from this reference. In most modern geographic coordinate systems they range from -180° to 180°, with positive values east of Greenwich and negative values west; some conventions use 0–360°.

These angles correspond to meridians, lines that traverse the globe from pole to pole. The longitude of a location is the angle between the prime meridian and the meridian passing through that location, measured along the equator. Distances represented by one degree of longitude vary with latitude; at the equator one degree is about 111.32 kilometers, decreasing toward the poles as the meridians converge.

Measurements are commonly given in decimal degrees or in degrees, minutes, and seconds. One degree equals 60 minutes, and one minute equals 60 seconds.

Practical uses include navigation, cartography, surveying, and GPS. Time zones are related to longitude, with each roughly 15° of longitude corresponding to one hour of time difference; the International Date Line at roughly ±180° marks a change in civil date. The Greenwich meridian was established as the world standard in the 19th century.

Related concepts include breedtegraden (latitude) and geographic coordinate systems such as WGS84. Lengtegraden provide the east–west component of a location’s global coordinates, complementing breedtegraden to specify exact positions on Earth.