One-Meter Level Kinematic Point Positioning Using Precise Orbits and Satellite Clock Corrections

The objective of this paper is to investigate the level of performance achievable in single point positioning mode with precise post-mission orbits and satellite clock corrections. Selective Availability results in satellite clock dither of up to 30 cm/s. In order to recover accurate single point positions, both precise orbits and satellite clock correction parameters are required. The satellite clock correction parameters, in view of their high variability, should be available at a sufficiently close interval to permit accurate interpolation. In 1993, the Geodetic Survey Division (GSD) of Natural Resources Canada (NRCan) began offering both orbit and satellite clock correction parameters as part of its post-mission GPS service. The quality of these parameters are investigated herein using shipborne data collected over a six-day period off the coast of Vancouver Island in October 1993 with narrow correlator spacing, single frequency, 1 O-channel C/A code receivers. A six-day precise orbit data set, including satellite clock corrections at 30- second intervals, was obtained from GSD in the IERS Terrestrial Reference Frame (ITRF) whose absolute coordinates are accurate to better than 10 cm and consistent with WGS84 within 0.1 ppm. Code measurements were used to obtain the single point positions at every second. Differentially corrected GPS positions were obtained separately to assess the accuracy of the above single point positions. The consistency of the single point positions, in terms of rms agreement with the DGPS positions, is of the order of 1 m in latitude and longitude, and 2-4 m in height. This level of agreement is considered excellent when the various error sources affecting the GPS positions are considered.