Global Navigation Satellite Systems01/01/1970 |
| Infrastructure Status and Developments |
| The concept of GNSS was first introduced by the European Space Agency (ESA), the European Commission (EC) and Eurocontrol in the early nineties. They defined requirements for a European GPS augmentation system, GNSS-1, and a full European satellite navigation system, GNSS-2, later together renamed EGNOS (European Geostationary Navigation Overlay System) and Galileo. Satellite navigation infrastructure status and developments are described here. |
| By Jac Spaans |
Nowadays the term GNSS is used for the system of systems comprising GPS and GLONASS, with the later addition of Galileo. Satellite-based and ground-based augmentation systems (SBAS and GBAS) were introduced to augment GPS and GLONASS. Hydrographers were early users of GPS, even long before the system was declared Fully Operational Capable (FOC) on 17th July 1995. Satellite positioning is now widely used in the great majority of hydrographic applications. However, over the coming decade the advent of Galileo, modernisation of GPS and the restoration of GLONASS will dramatically improve the performance of satellite positioning for both standalone and differential use, especially when using the combined systems.
PPP Programme The Galileo project is a public-private partnership (PPP) programme. ESA and the EC (1.2B€) will finance Phase 1, the in-orbit-validation (IOV) phase, and it will be carried out under the responsibility of a joint ESA/EC office: the Galileo Joint Undertaking (GJU). In December 2005 the Galileo GIOVE-A test satellite was successfully launched, and performs well in space. Notification of frequency filing at ITU took place on 8th and 9th March 2006. On 23rd May 2006, the Galileo Joint Undertaking released the newest Interface Control Document (ICD) for the OS signal in space for receiver manufacturers, see www.galileoju.com. On 19th January 2006 a 1B€ contract was signed between ESA and Galileo Industries GmbH on the IOV phase, guaranteeing four working satellites in orbit by 2008. More than a thousand highly skilled experts in more than a hundred companies are now at work in Europe to fulfil contractual obligations. The next phase is deployment, wherein the system will be completed to number thirty satellites, and ground infrastructure will also be completed. The cost of this phase is estimated to be 2.4B€, a third of which to be carried by EC/ESA and two thirds by a private concession-aire. Negotiations between the EC/ESA and the earmarked concession-aire have been struggling on since 2004; finalisation is not expected before the end of 2006. The GJU will then end its work and hand over the public responsibilities to the Galileo Supervisory Authority (GSA). This authority will act as the legal public owner of Galileo, responsible for its development, maintenance and certification, and acting as licensing authority to ensure that the Concessionaire meets its contractual obligations. Details of the concession contract are now further worked out, notably on risk sharing between public and private and between the private partners. Maintenance and replenishment of the infrastructure (220 M€/y) is part of the contract, as its lifetime is twenty years. Running GJU contracts have to be handed over to the GSA and/or Concession-aire. The content of Galileo services as described above could be modified by negotiations between GJU and the earmarked Concessionaire. It is agreed between Concessionaire partners that the locations will be:
Two consortia were initially bidding for the concession. However, the GJU has accepted a merger between them "because the separate bids were complementary and the EU taxpayer would benefit from this merger". Israel is participating, investing 18M€ in the Galileo project through the MATIMOP Center. China is also participating, with 200M€ in the GJU and signed contracts for a number of development projects. Australia has submitted a proposal to ESA for installation of a Galileo Sensor Station. Co-operation contracts have been signed with India, Morocco, Ukraine and South Korea; negotiations and talks are ongoing with several other countries in South America and Asia. SBAS Systems The US Wide Area Augmentation System (WAAS) is basically designed for aeronautical use, although other users have free access. Via geostationary (GEO) satellites the system provides additional GPS ranging, differential corrections and integrity information (6 seconds time to alarm), computed from information collected from 25 reference stations in the US; the system is therefore only usable in the US coverage area. It can be extended to other areas within GEO coverage when reference stations are installed in that area. In the three years of operation, approaches with vertical WAAS guidance have not suffered from vertical errors in GPS/WAAS of more than 11 metres and no hazardous misleading information (HMI) has been reported. WAAS will undergo a considerable upgrade over coming years. From 2015 onwards L5 corrections will be included. Interoperable with the US WAAS system, Europe has developed the EGNOS system and Japan the MSAS system. By extending reference stations in these areas both systems can be extended to adjacent areas. In July 2005 Initial Operations of EGNOS began on the part of the contractor ESSP in Brussels, a company formed by ESA and a number of European Air Traffic Service providers. SoL services are planned to be operational by mid-2007. Measured horizontal accuracies within the EGNOS coverage area are in the order of 1m. EGNOS information is also distributed over the internet through SISNET. Later in the Galileo development phase the EGNOS system will be integrated with Galileo and operated by the Concessionaire. India is developing its own SBAS named GAGAN; China is developing a similar system called BEIDOU. The Quasi Zenith Satellite System (QZSS) is a Japanese PPP project that will supplement GPS with three satellites in highly elliptical orbits in order to have at least one satellite near zenith in Japan at all times and so improve availability and accuracy of GPS in urban canyons etc. The first satellite is planned for 2008; it will carry Hydrogen Maser clocks. The URE is expected to be around 30cm. The FUGRO Starfix and SeaSTAR are commercial SBAS systems for offshore survey work; the FUGRO OmniSTAR-HP (High Performance) solution is a commercial dual-frequency SBAS that provides GPS augmentation of decimetre level accuracy. GBAS Hundreds of IALA maritime DGPS stations are operational worldwide. The system works in the former 300kHz maritime radio beacon band. The accuracy is in the order of 5m, often better. Many networks are extended for inland operations, notably in the US, where the NDGPS will have nation-wide coverage by the end of 2006. The intention is that double coverage will soon follow. For hydrographic operations, several RTK networks are operational providing corrections on GPS carrier-phase measurements. The accuracy of these augmentation systems is in the order of cm or better. |
| Biography of the author Jac Spaans sailed as a merchant navy officer from 1954 to 1960, before becoming a lecturer at the Nautical College in Amsterdam. He holds a MSc in Applied Mathematics from Delft University of Technology. He was one of the founding fathers of the Hydrographic Department of the Nautical College in Amsterdam in the early eighties, and served as vice-president of the Hydrographic Society Netherlands Branch. In 1980 he was appointed part-time professor in Navigation Technology at Delft University, and became full professor at the Royal Netherlands Naval College in 1989, a post from which he retired in 1999. Jac Spaans was also founding father of the Netherlands Institute of Navigation, of which he served as president from 1984 until 2004. He was chairman of the European Group of Institutes of Navigation (EUGIN) from 2000 to 2003 and president of the International Association of Institutes of Navigation from 1994 to 1997. |
|
| Archive |
| Archive > September 2006, volume 10, number 7 > Global Navigation Satellite Systems |
|
