Geographic coordinate system
Geographic coordinate system is a coordinate system used to identify positions on Earth by using latitude and longitude. It is one of the main systems used in geography, cartography, navigation, surveying, and digital mapping.
The system divides the surface of the Earth into angular measurements. Latitude measures position north or south of the Equator, while longitude measures position east or west of the Prime meridian. Together, these two values allow a place to be described as a point on the Earth's surface.
Structure
[edit | edit source]A geographic coordinate system is based on the shape of the Earth. Since the Earth is not a perfect sphere, modern coordinate systems use a mathematical model called an ellipsoid. This model allows positions to be measured in a consistent way.
A full coordinate system usually includes a datum. A datum defines how the mathematical model of the Earth is placed in relation to the real Earth. Different datums can give slightly different coordinate values for the same location.
The most widely used modern datum is WGS 84, which is used by the Global Positioning System and many digital maps.
Latitude
[edit | edit source]Latitude measures how far a location is north or south of the Equator. It is measured in degrees, from 0° at the Equator to 90° at the North Pole or 90° at the South Pole.
Northern latitudes are marked with N or a positive value. Southern latitudes are marked with S or a negative value.
Longitude
[edit | edit source]Longitude measures how far a location is east or west of the Prime meridian. It is measured in degrees, from 0° at the Prime meridian to 180° east or west.
Eastern longitudes are marked with E or a positive value. Western longitudes are marked with W or a negative value.
Coordinate formats
[edit | edit source]Geographic coordinates can be written in several formats. Degrees, minutes, and seconds are often used in traditional navigation and map records. Decimal degrees are commonly used in digital mapping, databases, and satellite navigation systems.
A coordinate may also include elevation or altitude when a three-dimensional position is needed. In that case, latitude and longitude describe the horizontal position, while elevation describes height above or below a reference level.
Use
[edit | edit source]Geographic coordinate systems are used to record the position of cities, borders, roads, buildings, natural features, and other places. They are also used in navigation systems, military mapping, aviation, maritime travel, land surveying, and geographic information systems.
On maps, coordinates help connect a real-world location to a fixed point on the map surface. Digital systems use coordinates to store, search, compare, and display geographic data.