Radio Navigation services

To aid the vessels’ radar navigation, radar reflectors and/or racons have often been installed in traditional aids to navigation. The Finnish Transport Agency provides a DGNSS service according to international standards to aid satellite navigation.

DGNSS service

The Finnish Transport Agency provides a correction data service to aid satellite navigation in the coastal waters and in the Saimaa deep channel. The frequency of the correction transmissions is 300 kHz. By combining the positioning data of the GPS satellite and the correction data provided by the service, vessels can determine their position with great accuracy and reliability.

The accuracy of the positioning data has been specified at <10 m 95 % of the time. In practice the accuracy is in the range of 1-2 metres 95% of the time.

Still, the signal received from the GPS navigation satellites does not provide real time data about the accuracy (integrity information) of the transmissions. That is why it is still absolutely necessary to use correction data in merchant shipping.

Transmitting Station ID	Reference Station ID	Position (Lat / Lon)	Coverage(km)	Frequency (kHz)	Bit rate (bit/s)
Porkkala (400)	600	59N58 / 24E23	250	293.5	100
Mäntyluoto (401)	601	61N36 / 21E28	250	287.5	100
Puumala (402)	602	61N24 / 28E14	70	290.0	100
Outokumpu (403)	603	62N41 / 29E01	70	304.5	100
Turku (404)	604	60N26 / 22E13	200	301.5	100
Marjaniemi (405)	605	65N02 / 24E34	250	314.5	100
Klamila (406)	606	60N30 / 27E26	250	287.0	100
Haarajoki (407)	607	60N31 / 25E10	250	292.5	100
Kokkola (408)	608	63N52 / 23E11	250	290.5	100

Radar reflector

Thousands of radar reflectors have been installed along our waterways to aid radar navigation. These are constructed so as to give an especially good radar echo. Radar reflectors are passive devices, which do not require regular overhaul or energy sources and are therefore very reliable. Occasionally echoes caused by ice masses or bad weather can impair the registering of the response by a radar reflector or some other radar target.

Racons

The number of racons installed along the waterways is presently about 70. A racon is a combination of a radio transmitter and a receiver, which when it has received the radar signal of the vessel, determines its frequency and responds with a signal on the same frequency with a special ID signal, which puts an easily recognisable image on the radar display.

The ID of the most widely used racons is the morse character T, composed of one long dash, but other IDs based on the morse code are also used. All racons used in Finland transmit a response on frequency 9 GHz (3 cm) and the majority also on 3 GHz (10 cm) to the radar signal.

The racons are active devices requiring regular overhaul and an energy source, whereby they are more vulnerable to malfunctions than radar reflectors. Occasionally echoes caused by ice masses or bad weather can impair the registering of the response by a racon or some other radar target.