Finnish Permanent GNSS Network, FinnRef
Hannu Koivula et al.
The National Land Survey of Finland (NLS) operates a nation-wide GNSS network of 20 stations. All stations, equipped with individually calibrated choke ring antennas and GNSS-receivers, track 1 Hz data from GPS, Glonass, Galileo, Beidou and SBAS. The data are streamed to the processing center of the NLS, where error modeling takes place. DGNSS corrections are transmitted through an IP network using NTRIP protocol and RTCM standards. The RINEX data of all the stations are stored for post processing purposes. Both DGNSS correction and RINEX data are freely available open data. The Finnish Geospatial Research Institute (FGI), the research unit of the NLS, maintains the coordinate system of Finland, the national ETRS89 realization EUREF-FIN. The time series of daily RINEX data are analyzed for monitoring the deformations of the EUREF-FIN. The frame is mainly deformed due to the postglacial rebound and plate tectonics. Due to the crustal deformation the relation between ITRF (International Terrestrial Reference Frame) and EUREF-FIN is not accurately known without constant monitoring. The FGI can open any GNSS data, including NRTK (Network RTK) corrections for educational, development and research purposes. The NRTK service will be improved so that it fulfills the internal surveying needs of the NLS. For this purpose the NLS has initiated a project for 2017-2019 to densify FinnRef with 20-30 new GNSS stations. Starting 2019 the FinnRef reference stations will be used as base stations for aerial survey work and the NRTK service by 400 NLS surveyors for RTK. FinnRef, with 40-50 stations, will be the highest order network of the Finnish coordinate system. All FinnRef stations will be connected to the precise levelling network. The height is further transferred to the ARP of the GNSS antenna by tachymeter with sub mm accuracy. These data together with an accurate geoid model may offer means for accurately maintaining the height system in the future. Concrete pillars will be constructed for absolute gravity measurements at a selection of the FinnRef stations. They will in the future serve as first order gravity network.
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