Mitigation of Tropospheric Effects in Local and Regional GPS Networks

Although modern technologies, especially space borne techniques, provoked a revolutionary advance in geodetic sciences, atmospheric refraction still remains a persistent problem. Modelling the atmospheric effects and estimation of tropospheric parameters are two methods to reduce the tropospheric biases. In this paper the development and testing of both methods, separately and in combination, are presented for applications in local and regional GPS-networks. The atmospheric state variables are modelled in four dimensions (space and time) based on operational ground measurements. Parameter estimation and collocation techniques are applied for modelling. By integration along the actual microwave paths the corresponding correction values are obtained. Compared to standard corrections the modelling method considerably reduces the rms of the GPS solution. An additional estimation of zenith path delays further reduces the rms. In a local network with considerable height differences (Swiss testnet ‘Turtmann’) the repeatability in height is clearly enhanced (up to a factor of 2) by introducing modelled path delays. For high precision applications the combination of modelled path delays and the estimation of tropospheric parameters is very promising.