Global satnav augmentation systems settle on common channels post-2020
The next decade’s aircraft pilots will be able to rely on enhanced, reliable satellite navigation signals on a seamless basis across much of the world, thanks to decisions made at the latest gathering of worldwide satnav augmentation system providers and experts.
The US Wide Area Augmentation System (WAAS) and European Geostationary Navigation Overlay Service (EGNOS) are leading examples of satellite-based augmentation systems (SBAS) that apply additional ground stations and satellite transponders to sharpen the accuracy and reliability of existing satnav services across given geographical regions.
These performance enhancements permit satnav to be employed for ‘safety-of-life’ services, especially aviation. Such systems are based on the US GPS for now, but plans are being laid to move to a multi-constellation design employing Europe’s Galileo, China’s Beidou and Russia’s Glonass satnav systems beyond 2020.
The latest 28th Satellite-based Augmentation Systems Interoperability Working Group (IWG), planning standardisation of SBAS systems to come, was hosted at ESA’s ESTEC technical centre at Noordwijk, the Netherlands, on 1–3 April.
All participants unanimously endorsed the ‘message definition’ for a new secondary SBAS channel – to be known as L5, along with the current L1 – for the planned second-generation SBAS systems, which will utilise dual-frequency multi-constellation signals.
Using dual frequencies greatly increases the accuracy of navigation systems, by allowing interference from the ionosphere – an electrically active outer layer of Earth’s atmosphere – to be largely subtracted from the final result.
“This definition is presented in what is called the Dual Frequency Multi-Constellation Definition document,” explained Didier Flament, representing ESA. “It represents the outcome of a four-year activity, which started at IWG 19 in Japan, back in 2010, coordinated between all IWG members under the technical leadership of ESA and French space agency CNES on the European side, and the Federal Aviation Authority (FAA) and Stanford University on the US side.
“The formal IWG review loop for the document took six months to conclude, with this IWG 28 then allowing endorsements to be gathered by SBAS project managers, culminating in formal signatures to the document.”
IWG members now intend to have this document accepted by the official international SBAS standardisation bodies: the International Civil Aviation Organisation, the US Radio Technical Commission for Aeronautics (RTCA) and the European Organisation for Civil Aviation Equipment.
“This next step is very important,” added Didier. “Not only for the coming 2016–22 implementation of the European EGNOS v3 but for implementation of other second generation SBAS in other regions of the world.”
The meeting also reported on the state of development of the other global SBAS systems. Along with the four operational systems – the US WAAS, European EGNOS, Japan’s Multi-functional Satellite Augmentation System (MSAS) and India’s GPS-aided geo-augmented navigation or GPS and geo-augmented navigation system (GAGAN) – these comprise South Korea’s KASS, China’s Beidou SBAS, Russia’s System for Differential Corrections and Monitoring (SDCM) and the West African Agency for Aerial Navigation Safety in Africa and Madagascar (ASECNA) SBAS.
The follow-up IWG meeting will take place in October, hosted by the FAA in Washington DC, in conjunction with the next RTCA meeting.
