A comparison of the VRS and MAC principles for network RTK

The Network Real-Time Kinematic (NRTK) GPS and GNSS technology is increasingly being utilised for a wide range of surveying and mapping applications, providing users with instant and highly accurate position information over distances of several tens of kilometres. This paper reviews the principles behind the two prevalent NRTK methodologies currently available, the Virtual Reference Station (VRS) approach and the Master-Auxiliary Concept (MAC). The inherent differences are outlined, and the two concepts are compared from both the user's and the network operator's perspective. While both methods are supported by the major GNSS equipment manufacturers and deliver positioning results at the same accuracy-level, there are significant differences in regards to the distribution of processing load, correction data transparency, legal traceability and required bandwidth. Several CORSnet-NSW sites are used to empirically determine the average bandwidth required for NRTK operation under typical conditions based on differently sized networks ranging from 3 to 9 reference stations. While the bandwidth required for MAC is significantly larger than for VRS, particularly for large cells, results show that it can be readily supported by common radios.