Pinpointing your location just by taking a quick look at a small mobile handset is something that we now take for granted. It’s something of a mystery to know how any of us ever arrived anywhere on time when we used to depend on paper-based maps, so great has become our dependency on the provision of an accurate position fix derived from data delivered by global navigation satellites.
For decades that data came from one of two systems: the American GPS (Global Positioning System) and the Russian GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema). GPS was launched by the US Government in 1978 and is operated by the US Air Force; development on GLONASS began in 1976 and the system is part of the Russian Space Agency. GPS is optimized for use by US military forces; the system’s accuracy for civilian users is somewhat reduced and there is poor coverage in polar regions. GLONASS was developed for Russian use, so its operation in the Southern hemisphere is less good.
Within Europe there was always veiled disquiet at reliance on positioning systems that were either controlled by the military or by a single country. Constantly changing geopolitical landscapes could always alter the widespread availability of such systems at a moment’s notice. Consequently, a variety of European scientists set to work in the late 1990s to ensure that coverage within Europe would always be available.
Since 2009, GPS has been complemented by EGNOS, the European Geostationary Navigation Overlay Service. This enhances the accuracy of the GPS ‘fix’ by providing accuracy for European and other users to within 1.5 metres. This level of precision had not previously been made available to civilian users of positioning services but is vital in situations such as during aircraft landing and take-off procedures as well as for ships and other vessels navigating narrow channels. As autonomous vehicles are introduced, high positional accuracy will become increasingly important too.
EGNOS is a precursor to a European system currently being rolled out, Galileo. This GNSS (global navigation satellite system) is fully interoperable with GPS and GLONASS. At its current stage of deployment, Galileo is providing initial services with somewhat restricted coverage, since not all of the planned 24 satellites have yet been launched. All 24 satellites will be launched by 2020. The initial services are offering ‘open service’ – providing coverage to the mass market – search and rescue (SAR) and ‘public regulated service’ – providing coverage in case of national emergencies.
After years of planning, the first two Galileo satellites were launched in 2011. Two further satellites were launched the next year. Extensive testing followed, ensuring that all of the concepts planned for the service were viable and met requirements. After this initial validation, there was another year of testing across Europe; teams drove 10 000km to pick up signals across the entire continent.
After this extensive test phase, the first two satellites with Full Operational Capacity (FOC) were launched in 2014. They were followed by other launches later that year and in the following two years. After these first 18 satellites were sent into orbit, control of the system was handed over by the European Space Agency to the European Global Navigation Satellite Systems Agency (GSA) in June 2017.
When rollout of the entire system is completed in 2020, there will be eight active satellites orbiting in three different planes in Middle Earth Orbit, plus another two satellites on standby in each plane in case of failure of an operational satellite. This structural design ensures that from any location on earth, the likelihood of being in sight of at least four satellites is above 90%. Most users will be able to see six to eight satellites at any one time, enabling them to fix their position with an accuracy of centimeters. The system should serve users in even those regions which are currently ill-served by GPS as well as providing coverage to those in high rise cities, where it will be aided by interoperability with GPS.
There are two ground-based control centres within Europe that offer mission management and satellite control functions. They are supported by a global network of sensor stations that provide data to the control centres over a redundant communications network. The control centres compute the data, confirming its integrity and synchronizing the satellites’ time signals with those of the ground-based clocks. Uplink stations are responsible for data transfer between the control centres and the satellites.
Although the Galileo system operates in the same frequency band as GPS, the two systems are separated from one another through the use of different signal modulation schemes. The Galileo system has been designed from the outset to operate using dual frequencies as standard. Galileo designers are also working to ensure the integrity and safety of the signals and data so that authentication is always verified.
One major advantage of the Galileo system lies in its SAR functionality. This is based around the existing Cospas-Sarsat system. The satellites have a transponder that transfers distress signals from the distress sender’s transmitter to regional rescue co-ordination centres. These centres initiate the rescue operation. Where the Galileo system differs from any extant system is that a response signal is transmitted to the sender of the distress signal to confirm that the signal has been received and that help is on the way.
Galileo represents a truly European partnership, with co-operation from companies and organizations throughout the region. One of those involved is u-blox, which launched its first range of GPS receivers back in 2007. The company has continued to track developments in the Galileo system and to incorporate the necessary changes in its product offerings.
Now the company is building on that experience with the announcement of a multi-party organization called Sapcorda. This joint venture aims to bring high precision GNSS positioning services to mass market applications with services designed to serve high volume automotive, industrial and consumer markets.
Knowing where you are to within a few centimeters is finally truly on the horizon.