New technology to monitor Global Navigation Satellite Systems

Imperial and partners develop new system to detect signal problems <em>– News</em>

Monday 8 December 2008
By Colin Smith

In a new £2.2 milion project, researchers from Imperial College London and partners will develop a system to monitor Global Navigation Satellite Systems (GNSS), enabling users to detect signal problems.

GNSS are a network of satellites orbiting the Earth that transmit precise microwave signals to receiving antennae on the ground. These signals are transmitted to GNSS receivers such as Global Positioning and Satellite (GPS) devices. These enable location, time and speed measurements to be taken.

Many users rely on the information received by their GNSS receivers to be reliable and accurate. These include motorists for direction finding, pilots for flying and landing planes safely, and captains who use it to navigate ships. Emergency services also use it to deploy ambulances and fire trucks along the fastest routes to emergencies.

However, the process of transmitting signals can be affected by a number of subtle failures along the way. This can happen because of satellite transmission problems, atmospheric interference, sunspot activity, or illegal jamming. This affects signal quality and thus the accuracy of information collected by GNSS receivers.

Currently, there are no effective methods for detecting whether signal quality has been compromised at their point of use. For example, if signals are faulty drivers don’t know if they are being directed by their GPS along the right route. Professor Washington Ochieng, from Imperial’s Department of Civil and Environmental Engineering, says this has the potential to cause problems.

New system will monitor signals received by GPS

“We’ve all heard the funny stories about drivers being led up the proverbial garden path because of problems with GPS devices. However impacts to signal quality can have serious consequences to shipping, transport and emergency services. Currently, there is no way for checking signal quality. This is a major problem for industry, government and the community, who need to know the information they are receiving is reliable,” says Professor Ochieng.

Professor Ochieng and his team are developing a new system that will improve ways of monitoring signal transmissions. They are developing portable probes that gather information. These can be put anywhere in the world to monitor signal quality. They are designed to continuously transmit information to a computer server, transmitting data that is important for monitoring signal quality only.

The server then uses computer programs to detect whether signal quality is deteriorating, interrupted, or jammed. Professor Ochieng says users can remotely access this information to assess whether their GNSS receivers are experiencing signal problems. He adds:

“If significant problems arise, users can revert to operational procedures designed for such an event. For instance, captains or pilots could switch to other computerised navigation tools to ensure the safety of crew, passengers or cargo is not jeopardised. In the case of motorists, they can turn off their GPS and simply revert back to age old navigation methods such as reading a roadmap.”

The name of the system is GNSS Availability, Accuracy, Reliability, anD, Integrity Assessment for Timing and Navigation – GAARDIAN. The project is funded by the Government’s Technology Strategy Board and the Engineering and Physical Sciences Research Council. It will run for 30 months and the team plan to have a fully operating prototype of their system for commercialisation.

The GAARDIAN consortium consists of Imperial College London, University of Bath, BT Design, Chronos Technology, and the Department for Innovation, Universities and Skills, the General Lighthouse Authority, the National Physical Laboratory, and Ordnance Survey.