GPS satellite precise ephemerides (GPS orbits and clock corrections) are computed from the data collected at the Canadian GPS reference stations stations (CACS) as well as IGS stations around the world. Replacing GPS’s broadcast ephemerides with precise ephemerides improves GPS positioning accuracy.
NRCan is one of 10 IGS data analysis centres involved in the computation of FINAL, RAPID and ULTRA RAPID precise ephemerides.
FINAL and RAPID ephemerides may be retrieved via the CSRS Online Database for use with GPS post-processing software. The best ephemerides available at the time will be provided (RAPID or FINAL).
Note: NRCan's ULTRA RAPID ephemerides are not available for download.
Precise ephemerides are packaged as daily (0:00 to 23:45 GPS Time) Precise Orbit and Clock files are at 15-minute interval. Precise Orbit files are in the NGS-SP3 format) and contain X, Y, Z satellite positions.
NRCan's CSRS-PPP free online post-processing service will use the best available ephemerides (FINAL, RAPID or ULTRA-RAPID).
Commercially available Precise Point Positioning (PPP) GPS software such as Leica IPAS Pro and ONPoz EZSurv also use Precise Ephemerides. The degree of compatibility between software packages will depend on the source of their Precise Ephemerides (you can inquire with the software manufacturer).