GNSS augmentation
Augmentationof aglobal navigation satellite system(GNSS) is a method of improving the navigation system's attributes, such as precision, reliability, and availability, through the integration of external information into the calculation process. There are many such systems in place, and they are generally named or described based on how the GNSS sensor receives the external information. Some systems transmit additional information about sources of error (such asclock drift,ephemeris,orionospheric delay), others provide direct measurements of how much the signal was off in the past, while a third group provides additional vehicle information to be integrated in the calculation process.
Satellite-based augmentation system
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Satellite-based augmentation systems(SBAS) support wide-area or regional augmentation through the use of additional satellite-broadcast messages. Using measurements from the ground stations, correction messages are created and sent to one or more satellites for broadcast to end users as differential signal. SBAS is sometimes synonymous with WADGPS, wide-areadifferential GPS.[1]
The SBAS that have been implemented or proposed include:
- TheWide Area Augmentation System(WAAS), operated by theUnited StatesFederal Aviation Administration(FAA).
- TheEuropean Geostationary Navigation Overlay Service(EGNOS), operated by theESSP(on behalf ofEU'sGSA).
- TheMulti-functional Satellite Augmentation System(MSAS), operated byJapan'sMinistry of Land, Infrastructure and TransportJapan Civil Aviation Bureau(JCAB).
- TheQuasi-Zenith Satellite System(QZSS), operated by Japan, started initial operations in November 2018. QZSS also operates in a non-SBAS mode called PNT, essentially acting as extra GNSS satellites.
- TheGPS-Aided GEO Augmented Navigation(GAGAN), operated by theAirports Authority of India.[2][3]
- TheSystem for Differential Corrections and Monitoring(SDCM), operated byRussia'sRoscosmosbased onGLONASS.
- TheBeiDou Satellite-Based Augmentation System(BDSBAS), proposed byChinabased onBeiDou.[4]
- TheSouthern Positioning Augmentation Network(SouthPAN), being developed by Australia and New Zealand, with initial services going live in September 2022.[5][6]
- TheWide Area GPS Enhancement(WAGE), operated by theUnited States Department of Defensefor use by military and authorized receivers.
- The commercialStarFire navigation system,operated byJohn DeereandC-NavPositioning Solutions (Oceaneering).
- The commercialStarfix DGPS SystemandOmniSTARsystem, operated byFugro.
- The commercialAtlas GNSS Global L-Band Correction Servicesystem, operated byHemisphere GNSS.
- TheGPS·C,short for GPS Correction, was a differential GPS data source for most of Canada, maintained by the Canadian Active Control System, part ofNatural Resources Canada– now decommissioned.
- The Australian SBAS using the Inmarsat 4F1 geostationary satellite, which suffered an outage in April 2023.[7][8]
Ground-based augmentation system
[edit]Ground-based augmentation system(GBAS) providesDifferential GPS(DGPS) corrections and integrity verification near an airport, providing approaches e.g. for runways that do not haveILSs. Reference receivers insurveyedpositions measure GPS deviations and calculate corrections emitted at 2 Hz throughVHF databroadcast (VDB) within 23 nmi (43 km). One GBAS supports up to 48approachesand covers manyrunwayends with more installation flexibility than an ILS with localizer and glideslope antennas at each end. A GBAS can provide multiple approaches to reducewake turbulenceand improveresilience,maintainingavailabilityand operations continuity.[9]
In December 2008, thePort Authority of New York and New Jerseyinvested $2.5 million to install a GBAS atNewark Airport (EWR)withContinental(nowUnited) equipping 15 aircraft for $1.1 million while theFAAcommitted $2.5 million to assess the technology. Honeywell’s SLS-4000 GBAS design was approved by the FAA in September 2009 and is still the only one. It offers Cat. 1instrument landingswith a 200 ft (61 m)decision heightand can be upgraded to a 100 ft (30 m) Cat. 2 with real-time monitoring of ionospheric conditions through SBAS, while the more precise Cat. 3 SLS-5000 is waiting for compatible airliners. The first installations were approved in EWR in 2012 andHouston / IAHin 2013. The Port Authority recommends a GBAS forNew York JFKandLaGuardia(LGA) to alleviate congestion. Newark and Houston GBAS were upgraded to Cat. 2,Seattle-Tacoma,San FranciscoSFO,JFK and LGA are expected next.[9]
Among the 20 Honeywell GBAS installations worldwide, the other U.S. installations are: Honeywell's test facility inJohnson County,Kansas; the FAA Technical Center atAtlantic City International Airport,New Jersey; Boeing's test facility inGrant County,Washington; the B787 plant inCharleston International,South Carolina; andAnoka County–Blaine Airportnear Minneapolis. Airports equipped in Europe areBremen,Frankfurt,MálagaandZurich. in Asia-Pacific, airport with installations areChennai,Kuala Lumpur,Melbourne,Seoul-Gimpo,Shanghai-PudongandSydney. Other locations areSt. Helenain the South Atlantic,Punta Canain the Dominican Republic andRio de Janeiro–Galeão. There are around 100 Cat. 1 GBAS landing systems (GLS) installations inRussiawith Russian-specific technology.[9]
In the US, GBAS was previously known as theLocal-area augmentation systemwhile aSBASwith a ground references network providing GPS corrections is calledWAAS.
In the US, there were more WAASLPVapproaches reaching 200 ft (61 m) than Cat. 1 ILS approaches by March 2018. 1 GBAS costs $3–4 million; and $700,000 more for Cat. 2.[9]
By Spring 2018,Boeingdelivered 3,500 GLS-capable airliners, with 5,000 on order: GLS Cat. 2/3 is standard on the Boeing 747-8, 787 and 777 while GLS Cat. 1 is optional on the 737NG/MAX and GLS Cat. 2/3 will be offered from 2020. Airbusoffers GLS Cat. 1 withautolandon the A320, A330, A350 and A380.[9]
The FAA’sNextGenpromotes GBAS and GLS to increase airport capacity and to lower noise and weather delays. Boeing prefers FAA support than funding while theNational Air Traffic Controllers Associationargues rigid approaches will lower traffic management flexibility, losing throughput and capacity, a viewpoint shared byDelta Air Lines. SomeICAOmembers vetter[clarification needed]GBAS Approach Service Types-D (GAST-D) supporting Cat. 2/3 approach and landing.[9]
There are stricter Safety requirements on GBAS systems relative to SBAS systems since GBAS is intended mainly for the landing phase where real-time accuracy and signal integrity control is critical, especially when weather deteriorates to the extent that there is no visibility (CAT-I/II/III conditions) for which SBAS is not intended or suitable.[10]
Beyond airfields
[edit]The US Nationwide Differential GPS System (NDGPS) was an augmentation system for users on U.S. land and waterways. It was replaced by[dubious–discuss]NASA's Global Differential GPS (GDGPS) system, which supports a wide range of GNSS networks beyond GPS. The same GDGPS system underlies WAAS and A-GNSS implementation in the US.[11]
Ground stations may also be used to accumulate continuous GNSS observations to achievepost-hoccorrection of data to the centimeter level. Two example systems are the US Continuously Operating Reference Stations (CORS) and the International GNSS Service (IGS).[11]
Aircraft-based augmentation system (ABAS)
[edit]The augmentation may also take the form of additional information from navigation sensors being blended into the position calculation, or internal algorithms that improve the navigation performance. Many times the additionalavionicsoperate via separate principles from the GNSS and are not necessarily subject to the same sources of error or interference. A system such as this is referred to as an aircraft-based augmentation system (ABAS) by the ICAO. The most widely used form of ABAS isreceiver autonomous integrity monitoring(RAIM), which uses redundant GPS signals to ensure the integrity of the position solution, and to detect faulty signals.[12]
Additional sensors may include:
- eLORANreceivers
- Automatedcelestial navigationsystems
- Inertial navigation systems
- Distance measuring equipment,often multiple systems are used to create a positional fix (DME/DME). Can also be used with INS (DME/DME/INS).
- Simpledead reckoningsystems (composed of a gyro compass and a distance measurement)
See also
[edit]References
[edit]- ^Kee, C.; Parkinson, B. W.;Axelrad, P., Penina(Summer 1991)."Wide area differential GPS".Journal of the Institute of Navigation.38(2): 123–146.doi:10.1002/j.2161-4296.1991.tb01720.x.RetrievedJanuary 12,2023.
- ^"GAGAN System Certified for RNP0.1 Operations"(Press release).Indian Space Research Organisation.January 3, 2014. Archived fromthe originalon 2014-01-03.
- ^Radhakrishnan, S. Anil (January 11, 2014)."GAGAN system ready for operations".The Hindu.
- ^Li, Rui; Zheng, Shuaiyong; Wang, Ershen; Chen, Jinping; Feng, Shaojun; Wang, Dun; Dai, Liwen (March 16, 2020)."Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies".Satellite Navigation.1.doi:10.1186/s43020-020-00010-2.S2CID212734687.
- ^"Trial of accurate positioning".Geoscience Australia.2019-10-05.Retrieved2020-04-25.
- ^Australia, Geoscience (2024-04-24)."Southern Positioning Augmentation Network (SouthPAN)".Geoscience Australia.Retrieved2024-10-05.
- ^"Satellite Based Augmentation System for Australia 2017".8 July 2020.
- ^"Farmers forced to take the wheel as satellite outage cuts autosteering".ABC News.18 April 2023.
- ^abcdefBill Carey (Sep 11, 2018)."GPS Augmentation At The Airport, But U.S. Locales Lack System".Aviation Week & Space Technology.
- ^Lawrence, Deborah (September 5, 2011)."FAA Global Navigation Satellite System Update, ICG-6"(PDF).RetrievedNovember 23,2022.
- ^abUS Government page on GPS augmentation systems
- ^ICAO (2005).Global Navigation Satellite System (GNSS) Manual(PDF)(First ed.).