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Introduction to GAGAN & GAGAN Enabled Receiver

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Presentation on theme: "Introduction to GAGAN & GAGAN Enabled Receiver"— Presentation transcript:

1 Introduction to GAGAN & GAGAN Enabled Receiver
By 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


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 Receiver
By 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

28 Typical Airborne SBAS Receiver

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






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

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