Automated monitoring of CORSnet-NSW using the Bernese software

Global Navigation Satellite System (GNSS) observations are increasingly used for a wide range of applications, and networks of Continuously Operating Reference Stations (CORS) are being rapidly installed to provide centimetre-level relative positioning. It is becoming increasingly important to determine and report on the quality control of these installations. This is necessary for legal traceability of data and measurements as well as for long-term stability studies of station coordinates. This paper presents the automation of high-precision daily coordinate solutions of stations in CORSnet-NSW, using the Bernese software. CORSnet-NSW is a rapidly expanding network of CORS stations separated by significant distances (up to 275 km in remote regions) in the state of New South Wales, Australia. Coordinates are obtained in ITRF2005 and transformed into GDA94. The ongoing analysis of these coordinates can reveal: 1) Site specific velocities of a network at higher densities than those provided by the IGS network, 2) A medium density sampling of the local distortions present in the GDA94 datum and the distortions in ellipsoidal heights derived from the Australian Height Datum 1971 (AHD71) and AUSGeoid98, and 3) Trends in site coordinates revealing local ground deformation. GPS data collected over a short period (60 days) in 2009 is sufficient to calculate station coordinates at millimetre-level precision, and velocities with 2-4 mm/yr precision that agree with expected tectonic motions. Significant differences are shown to exist between the coordinates of CORSnet-NSW stations obtained from the Bernese solution and their published GDA94 and ellipsoidal height coordinates at the 0.2 m and 0.3 m levels horizontally and vertically, respectively. The published coordinates are calculated from local tie-surveys and retain local distortions in GDA94 and AHD71 for the benefit of local users. Network-RTK error modelling methods, legal traceability via national ‘Regulation 13’ position certification, and overlapping CORS networks will soon require station coordinates in a more homogeneous datum, such as ITRF. Ever-increasing GNSS accuracy will highlight the local distortions present in GDA94 and AHD71/AUSGeoid98 and cause possible confusion for users. For these reason the time has come to review and renew the national horizontal and vertical datums.