A geographic coordinate system defines two-dimensional coordinates based on the Earth’s surface. It has an angular unit of measure, prime meridian , and datum (which contains the spheroid). As shown in the image below, lines of longitude have X-coordinates between -180 and +180 degrees.

A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. A GCS includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid).

Latitude and longitude, coordinate system by means of which the position or location of any place on Earth’s surface can be determined and described. Latitude is a measurement of location north or south of the Equator. Longitude is a similar measurement east or west of the Greenwich meridian.

Learn about the different types and units of geographic coordinate systems, such as latitude and longitude, UTM, SPCS, and datums. Find out how to convert and use them for maps and GIS applications.

What is the difference between a geographic coordinate system (GCS) and a projected coordinate system (PCS) anyways? Here’s the short answer: A GCS defines where the data is located on the earth’s surface. A PCS tells the data how to draw on a flat surface, like on a paper map or a computer screen.

Latitude and longitude form a geographic coordinate system. Latitude specifies the north-south position of a point on Earth, while longitude defines its east-west position. Lines of latitude are parallel to each other and are horizontal.

A geographic coordinate system (GCS) is a reference framework that defines the locations of features on a model of the earth. It’s shaped like a globe—spherical. Its units are angular, usually degrees. A projected coordinate system (PCS) is flat.

WGS84 is the standard coordinate system for GPS, based on a global ellipsoid model. Learn how WGS84 defines locations on Earth, how it differs from other geodetic datums, and how to use it in GIS.

Learn how to use longitude and latitude to specify positions on the Earth's surface. Find out how parallels and meridians are defined and how they vary in length and angle.