# ECEF

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ECEF

ECEF stands for Earth-Centered, Earth-Fixed, and is a Cartesian coordinate system used for GPS, and is sometimes known as a "conventional terrestrial" system [Alfred Leick, 2004, "GPS Satellite Surveying", Wiley] . It represents positions as an X, Y, and Z coordinate. The point (0,0,0) denotes the mass center of the earth, hence the name Earth-Centered. The z-axis is defined as being parallel to the earth rotational axes, pointing towards north. The x-axis intersects the sphere of the earth at the 0° latitude, 0° longitude. This means the ECEF rotates with the earth around its z-axis. Therefore, coordinates of a point fixed on the surface of the earth do not change, hence the name earth-fixed. Conversion from a WGS84 Datum to ECEF can be used as an intermediate step in converting velocities to the North East Down coordinate system.

References

* [http://www.satsleuth.com/GPS_ECEF_Datum_transformation.htm ECEF datum transformation] Notes on converting ECEF coordinates to WGS-84 datum
* [http://www.microem.ru/pages/u_blox/tech/dataconvert/GPS.G1-X-00006.pdf Datum Transformations of GPS Positions Application Note] More clear notes on converting ECEF coordinates to WGS-84 datum
* [http://www.colorado.edu/geography/gcraft/notes/datum/datum.html Geodetic Datum Overview] Orientation of the coordinate system and additional information

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