On Constraining Zenith Tropospheric Delays in Processing of Local GPS Networks with Bernese Software

The aim of this research was to develop the best strategy for the mitigation of the tropospheric delays in processing of precise local GPS networks. With the requirement of sub-centimetre accuracy and the availability of precise IGS products, one of the ultimate accuracy limiting factors in GPS positioning is the tropospheric delay. This is especially true for the accuracy of the height component. In many precise GPS applications, e.g. ground deformation and displacement analyses, volcano monitoring, the vertical accuracy is of crucial importance.Several processing strategies for the troposphere modelling available in the Bernese software were applied and tested. The results from our research show that in the case of small networks (with baselines <10 km and point height differences < 100m)the best strategy is to use of a troposphere model in order to derive zenith tropospheric delays that are fixed in the adjustment. This allows to achieve mm-level accuracies of both horizontal and vertical coordinates. The estimation of the tropospheric delays from the GPS data does not provide satisfactory results, even in the case of a relative troposphere estimation.