What is Earth-Centered, Earth-Fixed (ECEF)?

The Earth-Centered, Earth-Fixed (ECEF) coordinate system is a three-dimensional Cartesian reference frame with its origin at the Earth’s center of mass. In ECEF, positions are represented by X, Y, and Z coordinates measured in meters. The X-axis points toward the intersection of the equator and the prime meridian (Greenwich), the Y-axis points toward the intersection of the equator and 90° east longitude, and the Z-axis points toward the North Pole. 

Unlike geographic coordinates (latitude, longitude, altitude), ECEF coordinates are fixed to the rotating Earth, making them ideal for satellite navigation and geodetic applications. ECEF is used as the foundational reference frame for GNSS systems and can be converted to geodetic coordinates (latitude and longitude) as needed for mapping and navigation tasks.

For a more detailed overview of coordinate systems, transformations, and reference frames, read our article What Are Reference Frames, Epochs and Coordinate Transformations In RTK?