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2 nd Australian based CGSIC Meeting Ground based Regional Augmentation System (GRAS). Keith McPherson, Manager GNSS. GRAS Definition.
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2nd Australian based CGSIC Meeting Ground based Regional Augmentation System (GRAS) Keith McPherson, Manager GNSS
GRAS Definition A system providing GNSS augmentation service by which the user receives information directly from ground-based transmitters, allowing continuous reception of the service over a large geographical area (200Nm+). The ground components may be interconnected in a network
Rationale behind GRAS • Availability of (D)GNSS is paramount for Air Traffic Management(ATM) development • Impact on both Navigation, Surveillance and Communications • Availability must be from gate-to-gate • Minimum of new systems for CNS – cost efficiency • Value added service to CNS/ATM – improved business cases • Available for all user groups at reasonable costs • High latitudes • National and/or Regional sovereign control of the service delivery is vital
Aircraft GNSS integrity feed… GPS/GLONASS/GALILEO GNSS Receiver Navigation datalink Communications datalink GRAS ADS-B Service
Alternative Augmentation - GRAS • Key Benefits • Enroute navigation over entire continent • Non-Precision Approaches • Approaches with vertical guidance (APV-II) • No single point of failure for whole system • Relatively inexpensive compared to US and European augmentation systems • Expected potential to further reduce current navigation aids
GRAS usage • En-route • APV I/II CAT I • Surface movement guidance • ADS-B Surveillance
Technical concept Automatic Ground Station selection VHF Data Links GBAS Format GRAS Data Link Large Small Airport Airport Terrestrial Data Link
GRAS Schematic (Operational Concept) Not to Scale VHF Transmitters • Using current VHF voice transmission sites • Connected by data-line to Master Control Station • Master Control Stations • Brisbane & Melbourne • Ceduna • Thursday I • Mackay • Canberra • Hobart • Ground Reference Stations • Broome • Carnavon • Perth • Darwin • Alice Springs Data Lines
GRAS Architecture GRAS Broadcast Interface to other systems, e.g. other GRAS stations or SBAS/EGNOS (external GRAS) Remote service monitoring etc. Ground network
VHF Cross-over Interference (None so far) Slots A & H Equal Power Level Slots A & B Equal Power Level Slots A & B Closer to Cooma
GNSS AUGMENTATION GRAS Navigation Surveillance En-route through APV to Surface navigation ATC, aircraft and surface vehicles
GRAS in perspective SBAS + Wide Coverage - Complexity Institutional GBAS + Local(23Nm) - Dedicated landing System Expensive ABAS + Autonomous - High End A/C GRAS + Regional service Step wise implementation Added value service - Line of sight
GRAS today • Sent to ICAO for standardisation (GNSSP) uses GBAS message format with minor changes • Solid manufacturing support • RTCA and EUROCAE MOPS and MASPS to be completed • Service identical to GBAS standard. • GRAS supports PVT and is compatible to GNSSP PVT • Need for broader understanding and inclusion in regional programs as an alternative, regional solution
ICAO Approval Status GRAS • Concept presented to ICAO • Air Navigation Commission tasked GNSS Panel to develop SARPs 1999 • Australia (Airservices) selected to lead SARPs development • Standards and Recommended Practices (SARPs) • November 2000 - Concept of Operations developed • March 2001 - first draft of SARPs distributed • November 2001 - text mostly accepted by ICAO • October 2002 - final text agreed • 2002-2003 - validation process • April 2003 - approval sought from GNSS Panel
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