Satellite navigation service interference in Finland

Global Navigation Satellite Systems (GNSS) are used in many critical areas of society, such as rescue and logistics on land, at sea and in the air. Many applications on smart phones and smart devices also use satellite positioning. The best-known satellite navigation systems are the American GPS, the European Galileo, the Russian GLONASS and the Chinese BeiDou. Satellite navigation services facilitate operations and increase safety in many sectors.

Traficom is responsible for monitoring the use of frequencies and of interference analysis in Finland.

Traficom's mission is to ensure the efficient and undisturbed use of the radio spectrum. Traficom monitors the use of the spectrum and eliminates radio interference on the basis of incident reports received or its own monitoring. Traficom's responsibilities cover all types of radio traffic and frequency bands, including interference detected in GNSS services.

Traficom has the capability to detect and locate signals that may interfere with satellite positioning throughout Finland, and a comprehensive picture of interference on land, at sea and in the air. The agency closely monitors the performance of satellite navigation services and, in its role as the transport safety authority, will also react to any interference, if necessary.

Traficom monitors all GNSS frequencies throughout Finland and also receives automatic alerts in case of anomalies from land areas. The monitoring also covers the marine areas of the Gulf of Finland.

In-flight GPS interference in aviation

Before March 2022, GPS interference in aviation in Finland was rare. At the beginning of March 2022, however, there was a period of a few days during which numerous incidents were detected in Finland. The situation then calmed down until January 2024 when interference started in southern Finland and has continued on a daily basis since then. Typically, air navigation service providers and Finnish airlines report incidents detected in Finnish territory to Traficom. Finnish airlines also report incidents abroad. 

*From 1.5.2024, the criteria for reporting to Traficom were revised, as GPS interference has become so common over the last few years that reporting every incident does not provide additional information on the phenomenon. The current criteria are also more in line with the reporting criteria of other EU countries. This change is reflected in the statistics as a decrease in the number of reports since May.

In addition to occurrence reports, Traficom also monitors the evolution of the GPS interference situation in aviation using other sources of information, such as Traficom's own frequency monitoring and ADS-B data transmitted by aircraft. 

The impact of GPS interference on aviation safety

Aircraft have alternative navigation systems that are used when GPS signals are not available. With the help of these and, if necessary, air traffic control, an aircraft can safely navigate to its destination or to an alternate airport Airports have traditional ground-based approach systems that do not require a GPS signal.

While backup systems allow safe navigation, managing GPS interference does create an extra workload for flight crews. Similarly, the workload of air traffic controllers increases if several aircraft have to rely on air traffic control assistance. The GPS signal also provides accurate time information, which is used in many aircraft systems. Interference can therefore also affect aircraft systems other than just navigation. 

GNSS interference in waterway transport

In waterway transport, there were hardly any GNSS interference reports from Finnish territorial waters before 2024. During the summer of 2024, GNSS interference became more frequent, especially in the eastern Gulf of Finland which has caused interruptions in GNSS reception. Such incidents reduce the reliability of positioning in shipping. Interference has occurred on an almost weekly basis with sometimes several reports of it per day. As a rule, the observations and reports have come from professional seafarers. Just one report from a recreational sailor has been received. In the Kotka-Hamina area in particular, many incidents have been reported due to the proximity of the area to the Russian border and the high volume of vessel traffic. All GNSS interference for waterway transport has been reported from the Gulf of Finland.

In the professional maritime sector, vessels use many GNSS receivers and other navigation methods, the most important of which is radar. These can help vessels to navigate safely despite interference. Checking the condition of the equipment and cabling as well as optimal antenna placement can help to achieve the best possible GNSS reception.

For shipping in the Gulf of Finland, vessels should be prepared for momentary or regional GNSS signal interruptions. Good seamanship skills should be maintained and navigation without satellite-based navigation aids is a good practice. Much of the equipment on board may be dependent on GNSS, which is something to be aware of when guarding against interference. For example, a radar plotter may use a GNSS-based compass to determine the direction of the vessel meaning that, in the event of a disturbance, the view may start to rotate.

Fintraffic's vessel traffic service, or VTS centres, control vessel traffic along the Finnish coast and on the busiest inland waterways, improving safety in case of incidents.

Terrestrial radio interference and reporting it

Terrestrial radio interference can be visible to an individual person, for example if a smartwatch, navigator or chart plotter shows a wrong location or has only intermittent positioning. Traficom has received five reports of terrestrial GNSS interference this year. In all these cases, a cause other than radio interference was found.

Radio interference and GNSS reception anomalies should always be reported. Traficom's e-services (External link). 

Based on these reports, the agency's own situational information is refined and a case-specific incident report is drawn up on the basis of these reports. 

Traficom detects small jammers regularly

Telecom regularly detects low-power jamming transmitters, or so-called jammers, in its own monitoring of spectrum use. Typically, these are small radio transmitters used in cars or other vehicles to mask the location of, for example, the vehicle, a tachograph or a phone. 

Because the signal from radio navigation satellites is very weak when it reaches the ground, it is easily masked by a low-power jamming transmitter. In practice, the signal emitted by a jamming transmitter interferes with or completely blocks the reception of the GNSS signal from space, making it impossible for the GNSS receiver to determine the position reliably. 

As a general rule, such equipment intended to interfere with the use of frequencies may not be used, imported, marketed, sold or transferred to another person anywhere in the EU. Unlawful interference with radio communications is also prohibited by law and is punishable under criminal law. 

Jammers can cause interference to other satellite positioning services within their range, which varies from tens to hundreds of metres. Traficom works to locate and deactivate such devices through incident reports and cooperates with the police when necessary.

Jammer sightings are made all over the country, but no related radio interference has been reported to Traficom. However, such small jammers can cause interference to GNSS reception in their area of influence, which is why Traficom is working to identify and eliminate all possible cases.

* Detection rates decreased in 2023 as jammers were deactivated when the issue gained media visibility.