The Finnish Permanet GPS Network FinnRef^®

Finnish permanent GPS network (FinnRef ^®) is maintained by the Finnish Geodetic Institute. The Finnish permanent GPS network FinnRef ^® is a part of the Fennoscandian Regional Permanent GPS Network, which was established by the Nordic Geodetic Commission in response to the initiative of the directors of the Nordic Mapping agencies. Finnref ^® creates a backbone for the EUREF-FIN coordinate system and provides a connection to international and national coordinate systems. FinnRef ^® is also used to study the postglacial rebound in Finland.

Figure 1. Finnish permanent GPS network FinnRef ^®.

Planning and building the network

The planning of the network started at the end of the 1992 when it was decided that the network of 12 stations will be established. In 1993 the masts of Virolahti, Sodankylä, Tuorla, Vaasa, and Joensuu stations were built. The first observations were made on these stations in the same year during the DOSE93 campaign. These stations became operational in 1994. Kuusamo station was ready in the summer of 1996.

Figure 2.3 different antenna platforms of FinnRef ^®.

We use three different types of antenna platforms (Fig. 2a-c). The standard configuration is a 2.5 m high steel grid mast (Fig. 2a), which is used in Joensuu, Kuusamo, Sodankylä, Tuorla, Vaasa and Virolahti. A similar mast, but 5 m high is used in Kevo. Three stations (Olkiluoto, Kivetty and Romuvaara) have concrete pillars (Fig. 2b). The last two stations have higher masts. In Metsähovi is anchored 20 m height steel grid mast and in Oulu there is 8 m medal mast. In both cases the height of the GPS antenna is invarstabilized (Fig. 2c).

Equipment and the data

All the stations have Ashtech Z-12 GPS-receiver, Dorne Margolin type Choke Ring antenna, Vaisala meteorological station, modem and power source (see Fig. 2). Observing interval is 30 s and cut off angle is set to 5 degrees. The receiver stores L1 and L2 phase observations, C/A, P1 and P2 code observations, dopplers on both frequencies D1 and D2. In addition the the temperature, air pressure and humidity is stored every 30 s.

Figure 3.The antenna mast of Tuorla station with choke ring antenna and Vaisala meteorological station.

The data of the FinnRef ^® stations is collected to the FGI hourly using ADSL. Data is transferred to RINEX format and send to the International computation centres. Joensuu, Metsähovi, Sodankylä and Vaasa stations are part of the European wide EUREF Permanent Network (EPN). Metsähovi station is also part of IGS network.