Assessment of Network RTK performance using CORSnet-NSW

CORSnet-NSW is a rapidly growing network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) providing fundamental positioning infrastructure for New South Wales (NSW) that is accurate, reliable and easy to use. This positioning infrastructure supports a wide range of GNSS applications in areas such as surveying, agriculture, mining and construction. This paper briefly outlines the difference between the traditional, single-base Real Time Kinematic (RTK) and the Network RTK (NRTK) approaches. It continues to report on extensive testing carried out at several locations in eastern NSW to investigate the performance of the CORSnet-NSW NRTK service outside the Sydney metropolitan area, and with larger inter-CORS distances than those found in Sydney (25 km on average). Comparisons are made between NRTK and single-base RTK operation over varying distances to illustrate the performance of NRTK in the study areas. The achievable precision was investigated over multiple days at four different locations, while the achievable accuracy was determined by comparison to the State’s survey ground control network over several days in seven test areas exhibiting a range of NRTK scenarios and cell sizes. These tests have shown that while NRTK has the same ‘look and feel’ as single-base RTK, it produces superior coordinate results in regards to both precision and accuracy. The benefit of averaging observations over a window of 1-2 minutes and re-occupying points 10-30 minutes later is illustrated. It is also shown that coordinate quality (CQ) indicators provided by the GNSS rover equipment are often overly optimistic, even under the favourable satellite visibility and multipath conditions encountered during our tests, and should therefore be used with caution.