The spherical nature of Earth was known by the ancient Greeks, who also developed the concepts of latitude and longitude, … See more

The horizontal datum is the model used to measure positions on Earth. A specific point can have substantially different coordinates, depending on the datum used to make the measurement. There are hundreds o… See more

In geodetic coordinates, Earth's surface is approximated by an ellipsoid, and locations near the surface are described in terms of geodetic latitude (), longitude (), and ellipsoidal height (). See more

The difference in co-ordinates between datums is commonly referred to as datum shift. The datum shift between two particular datums can vary from one place to another within one country or region, and can be anyt… See more

A geodetic reference datum is a known and constant surface which is used to describe the location of unknown points on Earth. Since reference datums can have different radii and different center points, a specific point on Ea… See more

The Earth's tectonic plates move relative to one another in different directions at speeds on the order of 50 to 100 mm (2.0 to 3.9 in) per year. Therefore, locations on different plates are in motion relative to one another. For exampl… See more

• Axes conventions
• ECEF
• ECI (coordinates)
• Engineering datum
• Figure of the Earth… See more