Impact of surface meteorological measurements on GPS height determination

Although the topic of the positioning precision of the Global Positioning System (GPS) has been studied extensively, it focuses mostly on the error sources such as the ionospheric effect, antenna phase center variation and tropospheric influence. This investigation addresses the influence of the tropospheric effect on the results of the height determination. Used data are obtained from GPS receivers of a network and co-located surface meteorological instruments in 2003. Two approaches, parameter estimation and external correction, are utilized to correct the zenith tropospheric delay (ZTD) by applying the surface meteorological measurements (SMM) data. The GPS height can be affected by an incorrect pressure measurement up to a few meters, and the root-mean-square (RMS) of the daily solution can range from millimeters to a few centimeters, no matter which approach is adopted. The effect is less significant when using SMM for parameter estimation, but the trend of corrections on the GPS height is more consistent at either higher or lower altitudes. By external correction using SMM and Saastamoinen model, the GPS height reaches a few centimeters repeatability, while the RMS of the daily solution displays an improvement of about 2-3 mm.