29. What is a coordinate file?

A "coordinate" file for a CORS contains the officially adopted position and velocity for the site's antenna reference point (ARP) as well as for its L1 phase center. Hence, this file is also called a "position-velocity" file. This file may also contain officially adopted positions and velocities for selected geodetic monuments located near the CORS. Note that the ARP usually corresponds to the center point on the bottom of the pre-amp on the CORS antenna.

A coordinate file presents positions and velocities in both the International Terrestrial Reference Frame (ITRF) and the North American Datum of 1983 (NAD 83). Also, it presents positions in both geocentric cartesian coordinates (X, Y, Z) and in geodetic coordinates (latitude, longitude, and ellipsoidal height) for the GRS80 ellipsoid. NAD 83 positions given in these files are identical to those contained in the National Geodetic Survey's Integrated Database.

For additional information, including a discussion on how CORS positions and velocities are derived, set your web browser to http://www.ngs.noaa.gov/CORS/Derivation.html