How well does the virtual reference stations (VERS) system of GPS base stations perform in comparison to conventional RTL?

Abstract

In response to the recent growth in multiple reference station networks throughout the world, a pilot project of the Virtual Reference Station (VRS) network has been established in south-east Queensland. Independent testing of this network was required to establish its performance in post processed and real-time positioning, and its reliable coverage area. Tests were conducted at several sites, both inside and outside the network. GPS data from a single antenna was used to simultaneously record realtime positions derived from both the VRS base stations and a conventional base station. This data was analysed in terms of accuracy, precision and initialisation times. At the same time, raw data was logged for later analysis of the post processing capabilities of the VRS. Accuracy and precision estimates from the data collected showed that the VRS is at least comparable to, and in some instances may be considered superior to, conventional RTK. For example, during tests when low numbers of satellites were visible, the VRS-RTK was able to initialise in shorter times than conventional RTK. In general, the VRS-RTK proved to be a reliable substitute for conventional RTK using a single base station. In fact, VRS-RTK was shown to be more reliable and robust than conventional RTK, and in many instances was able to produce results where conventional RTK failed. VRS also showed great potential for post processing that, until now, has been largely ignored.