Grid Residual Tropospheric Corrections for Improved Differential GPS Positioning Over the Victoria GPS Network (GPSnet)

Tropospheric delay is one of the major error sources in GPS positioning. The delay of radio signals caused by the troposphere can range from 2 m at the zenith to 20 m at lower elevation angles. In a wide area differential system, tropospheric delays are corrected locally by users using an empirical tropospheric model, with or without meteorological observations. This can easily result in residual tropospheric errors of several centimetres to a few decimetres in positioning solutions. In this paper, the residuals between GPS-derived zenith tropospheric delays (ZTD) and model-computed ZTDs at reference stations of a continuously operating network are obtained. From these residuals, grid residual ZTDs are generated over the network coverage through Ordinary Kriging interpolation. Users can obtain the additional residual corrections for troposphere errors for improved differential positioning over a regional area. Experimental data from one week ZTD estimates from 17 GPSnet reference stations were analysed. Results show that the RMS ZTD accuracy of about 1cm is generally achievable over the Land Victoria GPS network coverage, using the proposed grid tropospheric correction strategies, which can support centimetre level positioning in the region.