1. Introduction to GAGAN & GAGAN Enabled ReceiverBy
Vineet Gera
Airports Authority of India
GAGAN

2. GNSS
A worldwide position and time determination system that includes one or more satellite constellations, aircraft receivers and system integrity monitoring, augmented as necessary to support the required navigation performance for the intended operation.
Core Satellite Constellations
Global Positioning System (GPS)
Global Navigation Satellite System (GLONASS)
Future Galileo & COMPASS Navigation Satellite System
GNSS Receiver
Augmentation Systems
GNSS Elements

3. GNSS Signal-in-Space Requirements
Accuracy – The difference between the estimated and actual aircraft position
Integrity – A measure of the trust which can be placed in the correctness of the information supplied by the total system. Integrity includes the ability of a system to provide timely and valid warnings to the user (alerts).
Continuity – The capability of the system to perform its function without unscheduled interruptions during the intended operation.
Availability – The portion of time during which the system is simultaneously delivering the required accuracy, integrity and continuity
GAGAN

4. Augmentation ? and Why Needed
Augmentation of a Global Navigation Satellite System (GNSS) is a method of improving the navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process.
Standalone GPS can not meet requirements of all phases of flight
Integrity is not guaranteed
All satellites are not monitored all the time
Time to alert could be minutes to hours
No indication of quality of service to the User.
Accuracy is not sufficient even with SA off, the vertical accuracy for 95% of the time is >10m.
Continuity and availability requirement shall be met.
GAGAN

5. GAGAN Augmentation Options Space Based Augmentations (SBAS)
Error Component
GBAS
SBAS
Satellite Clock
Common Mode Differencing
Estimation and Removal
Ephemeris
Ionosphere
Troposphere
Fixed Model
Multipath and Receiver Noise
Carrier Smoothing by User
Space Based Augmentations (SBAS)
WAAS, EGNOS, MSAS, GAGAN
Ground Based Augmentations(GBAS)
LAAS, GRAS
Aircraft Based Augmentations (ABAS)
RAIM, Inertials, Baro Altimeter
GAGAN

6. Augmentation
Fundamental concept behind AUGMENTATION is Differential GPS.
A technique for reducing the error in GPS-derived positions by using additional data from a reference GPS receiver at a known position.
Two Forms
Local Area Differential GPS
User’s GPS Receiver receives Pseudorange corrections from a Reference receiver, generally located within line of sight.
Corrections are lumped. Assumption is that the errors are common to User and Reference Receiver.
Wide Area Differential GPS
Corrections are determined based upon measurements from a network of Reference stations, distributed over a large geographical area.
Separate corrections for specific error sources.
GAGAN

7. Space Based Augmentation System
SBAS is an overlay System, requires establishing of
Ground Monitoring Stations
Monitors all GPS/GEO satellites in view and collects measurement data.
Master control station
Processes data, received from monitoring stations
Computes corrections & determines integrity.
Controls and Monitors SBAS system
Uplink station
Uplinks corrections and integrity information to the geostationary satellite.
Space segment
Broadcasts correction and integrity information to user community.
Additional ranging source.
Robust Communication Network
Stringent data transportation requirement with % availability.
GAGAN

8. DATA Communication Network - 1
INRES #
DATA Communication Network - 1
Data Communication Network - 2
PRN 128
PRN 127
INLUS-1
1SG 1RF
INLUS-2
INLUS-3
INMCC - 1
INMCC - 2
Bangalore
GAGAN Configuration
GEO In-orbit Spare
GPS Const.
Backup to INLUS 1/2
Delhi

9. How GAGAN Works Ground 15 Indian Reference Stations (INRES)
Two Indian Master Control Centre (INMCC)
Three Indian Land Uplink Stations (INLUS)
Space
Two operational GEOs
One In-orbit-spare
User
Civil Aviation Community
Non-Civil Aviation Users
Widely spread network of INRES track all the GPS satellites and SBAS GEO in view and forward all measurement data to Master control centre for further processing.
Master control centre uses the measurement data from the reference stations to generate differential corrections and integrity messages for the designated service volume.
These messages are transmitted through Indian Land Uplink stations to GAGAN GEO satellites.
GEOs have common coverage
GSAT-8/ 550 E, assigned PRN 127, Operational for Non-Safety-of-Life applications since Dec
GSAT-10/ 830 E, assigned PRN 128, currently undergoing integration with ground segment
GSAT 15/93.5, Launch planned in 2015, will work as in-orbit-spare.
User gets benefitted with improved positional accuracy and Integrity information

10. GAGAN Interoperability
GAGAN has been designed to meet ICAO defined standards on SBAS. GAGAN is compatible to other SBASs in the world and promises to provide seamless navigation.
GAGAN

11. GAGAN GAGAN Performance APV (Approach with Vertical Guidance)
RNP (Required Navigation Performance)
Horizontal Accuracy (95%)
7.6 m
72 m
Vertical Accuracy (95%) NA
Integrity
1 x 10-7 /150 sec.
1 x 10-7 /hr
Time to Alert
6.2 sec.
10 sec.
Continuity (over 15 seconds)
1-8 x 10-6
1 x 10-4
Availability
99%
Horizontal Alert Limit
40 m
0.1 NM
(185.2 m)
Vertical Alert Limit
50 m
Coverage
76% of Indian
Landmass
Indian FIR
GAGAN

12. GAGAN
GAGAN GEO Footprint
GSAT-8
GSAT-10
GAGAN

13. GAGAN Performance : Ahmedabad (accuracy)

14. GAGAN Performance : Bangalore

15. GAGAN Services Certified RNP 0.1 Service over Indian FIR
APV 1 Service over Indian Landmass, service expected to be certified by end of 2014

16. At Present GAGAN is certified for RNP 0. 1 Operations over Indian FIR
At Present GAGAN is certified for RNP 0.1 Operations over Indian FIR. Real-time GAGAN Performance can be seen at

17. GAGAN Enabled ReceiverBy
Vineet Gera
Airports Authority of India
GAGAN

18. GAGAN Terminology in Vogue WAAS Capable WAAS Enabled
Receiver can use SBAS services but the user must activate this function once only, or each time it starts up.
WAAS Enabled
Receiver activates SBAS reception by default.
Some manufactures clearly specify WAAS / EGNOS / MSAS / GAGAN enabled, others just say WAAS Capable / WAAS Enabled.
In general WAAS includes other SBAS systems too, but CAUTION “Clarify” from the supplier.
GAGAN

19. Conformance to ….
RTCA/DO-229D (Radio Technical Commission for Aeronautics)
Minimum Operational Performance Standards for GPS/WAAS Airborne Equipment
RTCA/DO-160E
Environmental Conditions and test Procedures for Airborne Equipment
RTCA/DO-310
Minimum Operational Performance Standards for GNSS Airborne Active Antenna Equipment for the L1 Frequency Band.
RTCA/DO-254
Design Assurance Guidance for Airborne Electronic Hardware
GAGAN

20. GAGAN Conformance to … RTCA/DO-178B
Software Considerations in Airborne Systems and Equipment Certification
RTCA Document DO-160 versions D, E, and F
Environmental Conditions and Test Procedures for Airborne Equipment
TSO-C145-b/c
Minimum Performance standards for Airborne Navigation Sensors, using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS)
TSO-C146c
Minimum performance standards for Class Gamma or Class Delta equipment, using GPS augmented by WAAS.
GAGAN

21. SBAS Receiver : Functional Classes
Beta
Sensor Only. Does Not Have Navigation Function
Generates Position, Velocity, Time, with Integrity
Typically Provides PVT To An FMS Which Provides Navigation Function
Gamma
Typical Panel Mount Receiver
Beta Sensor Plus Navigation Function With Procedure Database And User Controls
Delta
Beta Sensor With Navigation Function That Provides Deviations to A Final Approach Segment Only
Functions Like ILS (e.g. Does Not Support En Route Navigation)
GAGAN

22. Class Beta Configuration ( Position Sensor)
Antenna
Position
Integrity
(HPL, VPL)
Navigation Computer
Database
Controls
Pilot
Displays
Autopilot
Deviations from desired path,
Alerts
Deviations,
Steering
WAAS
Class
Beta
(Sensor)
Reference :
FAA TSO C-145

23. Class Gama Configuration ( Navigator )
Antenna
Navigation Computer
Database
Controls
Pilot
Displays
Autopilot
Deviations from desired path,
Alerts
Deviations,
Steering
Position
Sensor
WAAS Class Gamma
Reference :
FAA TSO C-146

24. Class Delta Configuration
Navigation Computer
Database
Controls
Pilot
Displays
Autopilot
Deviations from desired path,
Alerts
Position Sensor
Deviations,
Steering
WAAS Class Delta
Antenna

25. AAI Flight Calibration Aircraft

26. GAGAN GAGAN In Operation What is available from GAGAN ?
GAGAN Message, comprising of
Correction for each GPS satellite (in view)
Confidence Bounds (Integrity information),
What SBAS receiver does with GAGAN Messages ?
Corrects the computed position, using corrections
Computes protection levels, using confidence bounds
Protection level says that by how much the position in worst case could be Off , vertically and horizontally.
XPE < XPL < XAL, safe navigation is assured with high level of confidence.
GAGAN

27. SBAS Receiver Familiarization
GAGAN

28. Typical Airborne SBAS Receiver
GAGAN

29. Typical SBAS Receiver Performance Characteristics
Specification
Conformity
DO-229D / 301 / 228 / 178 B / 254 / 160
TSO – C145-b/c Beta, C146 – c Gama / Delta
General
MHz, L1 C/A code Receiver with SBAS Capability
Channels
10+ GPS, 2+ SBAS
Hor. Position Accuracy
3 m RMS
Diff. Position Accuracy
1 m RMS
Vertical Position Accuracy
5 m RMS
Velocity Accuracy
0.1 m/s
Sensitivity
GPS Acquisition / tracking
- 136 / -140 dBm
Characteristics
Specification
Approach Capability
LNAV, LNAV/VNAV, LPV
Altitude Aiding
Pressure, Baro-Aiding
TTFF (Cold / Warm Start )
90 / 66 seconds
Integrity
RAIM, FD/FDE, ALERT, BIT
Interface
RS-232, RS -422
Input Power
10 – 32 V DC
Power Consumption
5 W
Weight
Approx. 500 gms.

30. Real Time Position Display with 5Mtrs Grid
Speed
Direction

31. GAGAN HPL
GAGAN VPL

36. GAGAN GEOs
PRN 127 &128

37. Thank You
GAGAN

38. Backup Slides
GAGAN

39. SBAS Integrity Requirement 1/5
SBAS integrity is defined as the ability of the system to provide a timely warning to users when an individual correction or satellite should not be used for navigation.
Components of Integrity
Alarm condition
Time-To-Alert (TTA)
Hazardously Misleading Information (HMI)
GAGAN

40. SBAS Integrity Requirement 2/5
Alarm Condition exists when any of the following occur:
An active UDRE becomes invalid
The user-calculated protection level using active data does not bound the actual position error from positions created from any set of satellites
Data received from the satellite is insufficient to calculate corrections or integrity and to ensure that active data bounds the position error.
GAGAN

41. SBAS Integrity Requirement 3/5
Alarm is Used to Alert User that:
Corrections for a particular Satellite Have Changed; or
Corrections Can Not Be Used
Time to Alarm: Defined as the time period starting when an alarm condition occurs until the time the last bit of the first message in the alarm sequence arrives at the user’s antenna
10 seconds for ER/NPA
6.2 seconds for LNAV/VNAV
GAGAN

42. SBAS Integrity Requirement 4/5
Probability of HMI
For PA 10-7 / Approach (if Either or Both Occurs):
Computed VPL* < Actual Vertical Navigation System Error for Period of Time  Time To Alarm
Computed HPL* < Actual Radial Horizontal Navigation System Error for Period of Time  Time To Alarm
For ER/NPA: Computed HPL < Actual Radial Horizontal Navigation System Error for Period of Time  Time To Alarm; /hour
GAGAN

43. SBAS Integrity Requirement 5/5
SBAS User:
Applies Fast Corrections, Long Term Corrections, and Ionospheric Corrections
Calculates a Position Using GPS Range and Ephemeris Signals
Uses UDRE and GIVE to Calculate a VPL and HPL, which define a “Protection Cylinder”
Protection Cylinder Represents Uncertainty in the Calculated Position