Development and assessment of GPS virtual reference stations for RTK positioning

The past few years have seen substantial growth in multiple-reference-station networks which are used to overcome the limitations of standard real-time kinematic (RTK) systems. The use of a multiple-reference-station network, as opposed to a single reference station, results in a larger service area coverage, increased robustness, and a higher positioning accuracy. However, real-time application is still a difficult task to implement in practice. The virtual reference station (VRS) concept is an efficient method of transmitting corrections through a data link to the network users for RTK positioning. A novel method of creating VRS for high-precision RTK positioning has been developed and tested at the Nanyang Technological University (NTU). The emphasis has been on real-time implementation. A number of tests were conducted using the Singapore Integrated Multiple Reference Station Network (SIMRSN). The tests were done at different locations in Singapore to assess the achievable accuracy and initialization times for VRS RTK positioning using the NTU method. The results confirmed that VRS RTK positioning can be achieved to within 3-cm accuracy in horizontal position. Height accuracy is in the range of I to 5 cm. The average initialization time is within 2 min.