UK-based sat-nav trial to augment GPS performance

London satellite company Inmarsat is testing an overlay system to improve the performance of GPS signals received in the UK.

Britain's withdrawal from the European Union means it is no longer involved in the bloc's Galileo sat-nav system, nor its augmentation service called Egnos.

Overlay systems can reduce the errors in standard sat-nav fixes from metres down to just centimetres.

They're particularly useful in giving planes additional assurance in landing.

This is especially so in bad weather. But in the future, they're likely to play an increasing role across the transport sector as vehicles become more automated. Driverless trains, boats, trucks, buses and cars will be big beneficiaries.

Agriculture is becoming a major user, too, ensuring tractors know precisely where in a field to drill seed or apply fertiliser.

"An autonomous platform cannot know where it is to 25m (82ft); it's got to know at the very least where it is to just centimetres," said Todd McDonell, president, global government at Inmarsat.

"People seem to think this is only about aviation, and that's an obvious need, but land-based transportation, the maritime sector and agriculture have important needs as well," he told BBC News.

Inmarsat's system is in a trial phase at the moment. It's using an ageing satellite positioned out over the Atlantic to transmit the assurance data.

British partners on the project include Goonhilly Earth Station Limited in Cornwall and GMV NSL, which specialises in developing positioning, navigation and timing (PNT) technologies.

Augmentation systems are just that - they enhance the basic service by checking the accuracy of signals and warning users if there are issues of concern. But they are not a replacement for the underlying service.

The EU's Egnos system is dependent on Galileo and GPS. If they go down, Egnos has nothing to correct. Likewise for the UKSBAS - the UK Space-Based Augmentation System - and its use of GPS.

Nonetheless, such programmes are proving popular around the world.

America, China, Russia, Japan and India all run augmentation systems. And Inmarsat has recently become involved in a project to develop one for Australia and New Zealand.

"This has industrial base opportunity," Mr McDonell said.

"If the UK could create a sovereign service that produces certain benefits to the UK, to its economy, agriculture, transport and so on - then there's an opportunity in terms of developing receivers or other applications or technologies, not just for use in the UK but for export as well."

The future of PNT is moving increasingly towards a "system of systems" approach. That's in part because the likes of GPS and Galileo don't work everywhere (in buildings and in tunnels), but also because there's a concern modern economies have become a little too reliant on satellite-navigation signals.

The use of space-borne positioning and timing data is now ubiquitous, in everything from freight movement to the synchronisation of computer networks.

Without the resilience that comes with a diverse set of overlapping types of technology, economies run the risk of damaging shocks if they don't operate back-ups.

Since leaving the 27-member state European Union, the UK has been looking for possible alternatives to Galileo through its Space-Based Positioning Navigation and Timing Programme.

In addition to an augmentation service, the initiative could also lead to a constellation that provides primary PNT signals. Payloads to do this might eventually launch on satellites that are integrated into the OneWeb space-based internet broadband network, which the UK government helped buy out of bankruptcy in 2020.

Paul Bate, chief executive of the UK Space Agency, said: "Congratulations to Inmarsat, Goonhilly and GMV NSL on this impressive achievement.

"In recent years, the UK Space Agency has invested in the development of UK expertise in Positioning, Navigation and Timing, and the government's commitment to strengthening PNT resilience is set out in both the National Space Strategy and Integrated Review, given its importance to our critical national infrastructure and economy."

The UKSBAS signals being broadcast from the Inmarsat spacecraft in a geostationary slot at 53 degrees West has been constructed in co-operation with the US Federal Aviation Administration, the European Space Agency and the European Union Space Programme Agency to ensure there is no interference with American and European services.