Processing mixed-mode GPS networks for deformation monitoring applications

The Global Positioning System (GPS) can be utilised in a wide range of deformation monitoring applications. During the past few years a methodology has been developed for processing data collected by GPS networks consisting of a mixed set of single-frequency and dual-frequency receivers. The strategy is to deploy a few permanent GPS stations with dual-frequency, geodetic-grade receivers surrounding an ‘inner’ network of low-cost, single-frequency GPS receivers. The dual-frequency GPS network is used to generate a file of ‘corrections’, analogous to Wide Area DGPS correction models for the distance dependent biases. These ‘corrections’ are then applied to the doubledifferenced phase observations from the inner receivers to improve baseline accuracy (primarily through empirical modelling of the residual atmospheric biases that otherwise would be neglected). The performance of this configuration has been investigated by simulating such a two-stage GPS network using data collected in different geographical regions.