Carrier Phase Multipath Calibration of GPS Reference Stations

Based on available GPS reference network observations, a procedure for estimating carrier-phase multipath corrections was developed, implemented, and tested. This procedure consists of three steps: detection and localization of multipath-affected satellite signals, daily estimation of multipath errors, and combination of these daily estimates to obtain corrections for undifferenced L 1 and L 2 phase measurements. After application of these corrections, multipath errors can be significantly reduced for frequently used linear combinations of dual-frequency observations, but not for the original L 1 and L 2 observations themselves. The reason lies in the relatively small multipath effects compared with the larger influence of remaining ionospheric errors in the multipath corrections. The variability of carrier-phase multipath errors over 1 year showed that on some days with snow cover, multipath errors were altered. No similar effects could be found on days with continuous rainfall.