Transcript Slide 1

Prepared by:
Mohammad Khodakarami
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Global Navigation Satellite
System ( GNSS )
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CORE SATELLITES
The two core satellite constellations are :
 GPS
( provided by US )
 GLONASS ( provided by Russia )
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Navigation
GPS
Satellite
Communication
- Satellites
GLONASS
Satellite
- CPDLC
- Satvoice
ADS
CPDLC
AOC
ADS-B
ADS-B
Surveillance
- ADS/A & B
ADS
CPDLC
AOC
HFDL
AOC
Airline
Dispatch
ADS
C/PDLC
GES
Telecommunications
Network
Air Traffic Management
ATC
- Automatic coordination
ADS
CPDLC
AOC
VHF
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Augmentation
The existing core satellite constellation
alone do not meet strict aviation
requirements .
So requires augmentation .
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AUGMENTATION

ABAS (Aircraft Based Aug System )
Uses avionics on board aircraft
 SBAS (Sat Based Aug System)
Uses ground monitoring stations , then delivers
corrected information via GEO sat
 GBAS (Ground Based Aug System)
Uses ground monitoring stations , then via a VHF
data broadcast
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ABAS
ABAS can support en-route up to NPA ( nonprecision approaches ) , also GPS overlay app
 ABAS augments and/or integrates
GNSS information with
information available on-board the aircraft
The most common ABAS technique is RAIM
RAIM detects faulty signals and alerts the pilot
FDE is a feature in some avionics which have the
ability to exclude that satellite
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ABAS
 RAIM
requires a minimum of 5 visible
satellites for fault detection
 FDE uses a minimum of 6 satellites not
only to detect a faulty sat but also to
exclude it from the navigation solution
 Using a barometric altimeter reduces the
number of sources for RAIM and FDE by
one
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availability
RAIM
availability
FDE
availability
Without SA
En-route 99.99 En-route 99.8
NPA
99.70 NPA
89.5
With SA
En-route 100 En-route 99.92
NPA
99.99 NPA
99.91
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ABAS
 The
use of satellites from multiple GNSS
elements ( e.g. GPS + GLONASS ) or use
of SBAS can improve the availability of
RAIM and FDE
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SBAS
SBAS support en-route and terminal RNAV
operations (including APV) comprises :
 A network of ground reference stations
 Master stations to process collected data
 Uplink stations to send SBAS messages to
GEO satellites
 Transponders on these sats to broadcast
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SBAS
four SBASs being developed :
. EGNOS ( European )
. GAGAN ( Indian )
. MSAS
( Japanese )
. WAAS
( U.S )
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SBAS
 cooperating
with another state
 developing own SBAS .
 In any case it is the responsibility of the
state to monitor the performance of the
SBAS and issue NOTAM .
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GBAS
for a precision approach service to
provide deviation guidance for a final
approach segments .
a GBAS installation will typically provide
corrections that support approaches to
multiple runways at a single airport .
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GBAS
The nominal range is 20 nm
 Precision approach service
 GBAS positioning service (2D RNAV ops)
the SARPs for cat 2 and 3 precision
approaches are under development
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GNSS
According to annex 10 , any change in the
SARPs that will require the replacement or
update of GNSS requires a six year
advance notice .
Similarly , a six year notice is required of a
core or augmentation system provider who
plans to terminate the service provided .
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GNSS
 State
should evaluate 4 essential criteria :
accuracy
integrity (including time to alert)
continuity
availability
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ACCURACY

The difference between the estimated and actual
aircraft position
 Not repeatable as VOR or ILS
 GNSS errors can change over a period of hours
due to
1 . sat geometry changes ,
2 . the effects of ionosphere and
3 . aug system design
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INTEGRITY
 The
trust in the correctness of the
information supplied by the total system
 Includes the ability to alert the user when
the system should not be used
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CONTINUITY
 The
capability to perform function without
unscheduled interruptions during the
intended operation
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AVAILABILITY
 The
portion of time during which the
system is simultaneously delivering the
required accuracy , integrity and continuity
 The availability of GNSS is complicated by
the movement of satellites .
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GBAS

The nominal range is 20 nm
 A single GBAS for up to 49 precision
approaches within VDB coverage ,
 Serving several runways and possibly more than
one aerodrome .
 Provide 2 services
precision approach service
GBAS positioning service (2D RNAV in TMAs)
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GNSS PLANNING PROCESS

Cost-benefit analysis (CBA) It would be useful
for
 service providers
 regulators
 users
To work together and consider
 cost recovery
 revenue policy
 extra costs
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ADVANTAGES OF GNSS
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Support all phases of flight
Eliminate the need for a variety of ground and
airborne systems
Even early use of GNSS from 1993 based on
ABAS , delivered significant benefits
Accurate guidance in remote and oceanic areas
Avoiding the cost of fielding NAVAIDs
With traditional NAVAIDs , can support efficient
flight paths
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ADVANTAGES OF GNSS
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Design en-route and TMA airspace for max
capacity and min delays
Support efficient noise abatement procedures
Providing the possibility of lower climb gradients
and higher payloads
Improve airport usability , through lower minima
because of APV
Can allow continued operations with vertical
guidance to the new threshold
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ADVANTAGES OF GNSS
 Support
surface operations
 Support ADS and CPDLC
 Allow phased decommissioning of some or
all of the traditional NAVAIDs
 Can be implemented in stages , providing
benefits at each stage
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LIMITATIONS OF GNSS
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A major change for all members
aircraft operators
pilots
ATS personnel
Close coordination with other states
Gradual development of GNSS technology
High availability of service
Interference with GNSS signals affects
availability
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