“There is a demand for a coordinated effort towards effectively addressing this problem. The recently concluded seminar 'GNSS Interference 2019' was a step in the right direction,” says Sarang Thombre, research manager at The Finnish Geospatial Research Institute (FGI) of the National Land Survey of Finland.
Representatives from research organizations, universities, industry and government agencies of Finland, Sweden, Norway, and Denmark are collaborating through organizations such as the Nordic Institute of Navigation (NNF) to create awareness and counter-strategies.
GNSS signals are weak and vulnerable
“The GNSS signals transmitted from navigation satellites located more than 20 000 kilometers away are usually very weak at the time of reception, and susceptible to interference: a phenomenon where other radio signals disrupt the GNSS signals causing reduced positioning accuracy, or even the complete loss of position availability,” says Dr Zahidul Bhuiyan, research manager at the Finnish Geospatial Research Institute (FGI).
Fortunately, the detection of an interference on a GNSS signal is very much possible.
“In the Finnish Geospatial Research Institute, we have been actively working for the last couple of years with our international partners to seek a solution for GNSS interference monitoring, detection, classification and mitigation, so that the users of GNSS can use the service 24/7 resiliently,” Dr Bhuiyan says.
Most of the economy depends on GNSS
The Global Navigation Satellite System has long become an integral part of our day-to-day activities, varying from simple navigation guidance to more sophisticated timing applications, used to run our modern day life smoothly and in a carefree manner.
“In June 2017, Innovate UK, the Royal Institute of Navigation and the UKSA published a study performed by London Economics, which estimated the economic impact on the UK of a potential five-day disruption to the GNSS at £5.2 billion. Considering that the UK represents approximately 15% of the European GDP, escalating this figure at a European level would determine an economic impact of approximately £35 billion. This is equivalent to approximately 39 billion Euros,” compares Dr Pierluigi Mancini from the European Space Agency.
Alternatives and new actions are needed
Our dependency on the GNSS becomes a risk if there are no back up plans or alternatives.
“There is a need for governments, and critical infrastructure operators to increase the resilience, and robustness of their infrastructures, which in turn fosters the requirement of innovative upgraded reliable multi-technology PNT systems,” says Dr Mancini.
PNT systems are systems for positioning, timing and navigation, for example, inertial navigation methods and wireless network positioning and of course the GNSS.
According to Nicolai Gerrard from the Norwegian Communication Authority (Nkom), Nkom has observed the increase in the number of cases related to GNSS interference and is working to counteract this trend. Both field personnel and administration at Nkom are becoming experienced in identifying and punishing illegal use of GNSS-frequencies.
“Nkom is working for stronger cooperation and coordination with and between actors in affected sectors and relevant authorities,” says Mr Gerrard.
Interference is not the first suspect
Malfunction of GNSS signals is not always due to interference by a malicious party. Satellite measurements used to calculate positions are based on a chain of various factors. Any one of them can be affected. For example, a large number of trees or buildings located close to the receiver can block the signal.
Dr Anna Jensen from KTH – the Royal Institute of Technology, Sweden, presented her research on interference for high accuracy GNSS use in Denmark. Jensen presented a data analysis on a case in which signals from both GPS, Galileo and GLONASS were affected.
“Users spent a lot of time and many working hours on trying to find the reason when signal interference occurred, because in all cases presented, users first thought there was something wrong with the equipment or the way they used it, before they suspected interference. More information for GNSS users on the characteristics of interference would be beneficial,” says Dr Jensen.
Natural causes or jamming?
Radio frequency interference (RFI) to GNSS signals can be due to jamming or spoofing. Jamming is when a very high power unfriendly signal is transmitted over the GNSS signal frequencies completely overwhelming the signal of interest. In this case, positioning is unsuccessful.
Spoofing is when a high power unfriendly GNSS-identical signal is transmitted over the GNSS signal frequencies in order to confuse the receiver and force it to track the unfriendly signal, resulting in an erroneous position and time estimate. In this case, the user of GNSS signal gets wrong information.
The typical accuracy of a GNSS receiver designed for consumers is approximately five metres, but it can also be worse in certain conditions. In the worst case, the position calculated by the receiver can differ from the actual position by hundreds of metres, or even more, due to a satellite malfunction or an unusually high environmental or atmospheric interference.
Director of Department Sanna Kaasalainen, +358 50 369 6806, firstname.lastname@example.org
The seminar 'GNSS Interference 2019' was organized by the Nordic Institute of Navigation (NNF) and the Finnish Geospatial Research Institute (FGI)