Now the University of Nottingham and Royal Norwegian Naval Academy (RNoNA) are investigating how to prevent shipping GPS from being jammed in potential cyberattacks that could cause vessels to go off course and collide or end up stranded.
Modern ships are equipped with automated networked navigational systems, including differential GPS (DGPS), which offers more accurate positioning than traditional GPS.
However research has proved that these sensitive maritime DGPS receivers are also easy to disrupt with a simple GPS jamming device that can be purchased for about $50 on the market.
When ships are navigating through narrow inshore waters, this kind of disruption could result in inaccurate positional information and cause increased maritime accidents.
For the study, the researchers tested DGPS disruption in the busy shipping lanes of the Norwegian straits where navigational errors account for half of accidents.
"Main factors behind maritime accidents in this part of Norway are an influx of foreign vessels, coupled with quickly changing weather conditions and the dangerous nature of the narrow inshore waters,” said Dr. Lukasz Bonenberg, senior technical officer at Nottingham Geospatial Institute. "In these difficult conditions, with a need for high-accuracy navigation, there tends to be an over-dependence on DGPS technology, which can lead to a false feeling of security. These errors have increased significantly since the introduction of DGPS on most ships.
Jamming from a nearby cliff could potentially affect traffic and take a long time to correct.
“This may cause the maritime equivalent of a motorway pile-up," said Dr. Bonenberg.
Tests were conducted with a high-end surveying-grade receiver and antenna, which was placed on the shore with the jammer moving toward or away from the receiver on a small boat.
The overall goal of the trial was to measure the jamming effect. The researchers found that the DGPS receiver did not stop functioning altogether. Instead it gave false readings in the on-board navigation system with positional data moving more than 10 meters.
"Observed discrepancies of up to 10 meters are very hazardous, considering the narrow nature of the Norwegian straits, which are frequently affected by poor visibility," said Lieutenant Commander Oeystein Glomsvoll at RNoNA Navigation Centre.
Because GPS jammers are readily available and attention to the problem has increased in recent years, the team looked at a solution that would fix and maintain a transporter ship's position more accurately and quickly, using additional GPS signal frequencies instead of upgrading navigational systems on board.
The team suggests combining current receivers with the multi-frequency GLONASS receiver, an alternative navigation system to GPS.
This is because the frequency band of GPS and GLONASS signals together is much wider than dual L1 and L2 frequency GPS or GLONASS alone, increasing positional precision.
"The use of multi-constellation receivers and an increase in the frequencies received offers better jamming resilience for close-to-shore navigation,” said Dr. Bonenberg, from the Faculty of Engineering.
Data observed during this experiment suggests that implementing new, modernized signals will offer advantages similar to the multi-frequency GLONASS one.