Avcharges

1
2nd Australian based CGSIC Meeting Ground based
Regional Augmentation System (GRAS)
Keith McPherson, Manager GNSS
2
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
3
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

4
Aircraft GNSS integrity feed
GPS/GLONASS/GALILEO
GNSS Receiver
Navigation datalink
Communications datalink
GRAS
ADS-B Service
5
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
6
GRAS usage

• En-route
• APV I/II CAT I
• Surface movement guidance
• ADS-B Surveillance

7
GRAS Concept
8
Technical concept
Automatic Ground Station selection
VHF Data Links
GBAS Format
GRAS Data Link
Large
Small
Airport
Airport
Terrestrial Data Link
9
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
10
VHF Sites Across Australia
11
GRAS Architecture
GRAS Broadcast
Interface to other systems, e.g. other GRAS
stations or SBAS/EGNOS (external GRAS)
Remote service monitoring etc.
Ground network
12
(No Transcript)
13
(No Transcript)
14
VHF Cross-over Tests
15
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
16
(No Transcript)
17
GNSS AUGMENTATION
GRAS
Navigation
Surveillance
En-route through APV to Surface navigation
ATC, aircraft and surface vehicles
18
GRAS in perspective
SBAS Wide Coverage - Complexity Institutional
GBAS Local(23Nm) - Dedicated landing System Expe
nsive
ABAS Autonomous - High End A/C
GRAS Regional service Step wise
implementation Added value service - Line of sight
19
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

20
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

21
ANY QUESTIONS ??
Old Navigator
New Navigator