Carrier-Phase Multipath Calibration of GPS Reference Stations

ABSTRACT: 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 L1 and L2 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 L1 and L2 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.