European researchers are investigating whether a system that enhances the accuracy of satnav for aviation could also be used reliably at sea.
Results gathered by Belgium’s RV Belgica research vessel are being used to chart the maritime performance of Europe’s EGNOS satnav overlay service, which augments GPS data.
The Belgica is an all-purpose oceanographic research ship that spends around 200 days a year at sea, serving as a floating laboratory for Belgian universities and research institutes. Mainly operating in the southern North Sea, it is run by the Belgian Navy on behalf of the Royal Belgian Institute of Natural Sciences.
The ship has been fitted with a set of three receivers to pick up signals from EGNOS, and also from Galileo.
The third and fourth European Galileo satellites were launched in October, making it possible to validate the system’s positioning capability (which requires data from at least three satellites) before the rest of the constellation is deployed in the next few years.
“The receivers are continuously logging satnav signals, so that we can see the system performance during different sea conditions, while the ship is moving or stationary and out to sea or approaching harbour,” explained Massimo Crisci of ESA’s Radio Navigation Section.
“We’re interested in learning how the signals reflect – an unwanted effect known as ‘multipath’ – off the sea or from harbour infrastructure or nearby ships,” added fellow researcher David Jimenez-Baños. “Then close to shore there is also the potential for interference from local ship-tracking radar.
“What is crucial for EGNOS is to have an assurance of accuracy – what is the level of trust a user can have in the service?”
Covering all European territory via a trio of geostationary satellite transponders, EGNOS sharpens the accuracy of GPS signals. It corrects for interference from the electrically active ionosphere and adds information on reliability for a range of general and safety-critical uses across the continent.
Designed by ESA, the European Commission and Eurocontrol, the European Organisation for the Safety of Air Navigation, EGNOS is now available for guiding aircraft approaches to airport runways and can also be used for surface transport on land and sea.
This is the first systematic long-term study of EGNOS’s performance at sea. The investigation is using one commercial receiver, from Septentrio Satellite Navigation in Belgium, with two others developed by the research team.
The Belgica’s duties can take it into difficult environments for signal reception, such as near offshore wind farms.
The receivers have been put in place for a year under a cooperative data-sharing arrangement, with the potential for extension.