Service Technique de la Navigation Arienne GROUND BASED

Service Technique de la Navigation Aérienne GROUND BASED AUGMENTATION SYSTEM System Overview Christophe DEHAYNAIN Direction Générale de l’Aviation Civile GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar FRANCE Page 1

Service Technique de la Navigation Aérienne GROUND BASED AUGMENTATION SYSTEM Presentation Overview • • • GBAS OVERVIEW Why do we need an augmentation to GNSS ? Local Area Differential GNSS Principle GBAS Ground Segment GBAS Airborne Segment Conclusions CAR/SAM ATN/GNSS Seminar Page 2

Service Technique de la Navigation Aérienne GBAS Concept System Overview • ICAO Name : GBAS for Ground Based Augmentation System • Operational Coverage : – minimum : same as ILS – recommended : Omni directional (radius 23 NM) up to FL 100 and down to 12 ft • Data-Link Frequency range : 108 - 118 MHz (25 k. Hz spacing) • Operational objective : – minimum : Category 1 approach – optional : 2 D navigation (Positioning Service) • Localisation : Airport GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 3

Service Technique de la Navigation Aérienne GBAS Overview Do not mistake GBAS for : • DGPS, LADGPS : initial US generic names for GBAS concept • SCAT 1 or Special Category 1 : US RTCA standard defining a noninteroperable system for private use • LAAS : Local Area Augmentation System : present US name for GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 4

Service Technique de la Navigation Aérienne WHY GNSS NEEDS AN AUGMENTATION ? GPS Only Civil Aviation CATEGORY I Requirements PERFORMANCE H. 13 m V. 23 m 99% (RAIM) GBAS OVERVIEW ACCURACY (95%) AVAILABILITY H 16. 0 m V 4. 0 m 99. 75 % ? INTEGRITY 3, 5. 10 -7/ approach Time to alarm 6 s ? CONTINUITY OF SERVICE 10 -4 / approach (10 -5 / 15 s) CAR/SAM ATN/GNSS Seminar Page 5

Service Technique de la Navigation Aérienne LOCAL AREA DIFFERENTIAL PRINCIPLE I - Basic Principle • Measurements made by two receivers are affected by the same errors as long as these two receivers are not too far from each other RX 2 RX 1 GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 6

Service Technique de la Navigation Aérienne LOCAL AREA DIFFERENTIAL PRINCIPLE II - Differential Correction Calculation Actual SV Position Broadcast SV Position Calculated Range REF Measured Pseudoranges Corrections Calculation Differential Message Broadcast Known Reference Location USER – The first receiver in a reference station calculate these errors knowing its exact location (corrections calculated by the GBAS ground station) – The second receiver (the user) will use these corrections to correct its own measurements and increase the accuracy of these measurements GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 7

Service Technique de la Navigation Aérienne GBAS ground segment I - Basic architecture of a reference station Differential Message Broadcast Antenna GPS/GLONASS Antennas Receiving Unit (up to 4 Reference Receivers) Data Broadcast Unit Data processing for broadcast Raw Data PR, ephem. , time Data Processing Unit • Differential Corrections Calculation • Integrity Monitoring Functions • GBAS Messages Elaboration GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 8

Service Technique de la Navigation Aérienne GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 9

Service Technique de la Navigation Aérienne GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 10

Service Technique de la Navigation Aérienne GBAS ground segment II - VHF Data Broadcast (VDB) • GBAS VDB characteristics : – – – – VHF NAV band (108 - 118 MHz), channel spacing 25 k. Hz D 8 PSK (Differential 8 States Phase Shift Keying) modulation 2 Hz update rate (Pseudorange Corrections) 8 slots Time Division Multiple Access technique (16 per second) Horizontal Polarisation or Elliptical Polarisation (Recommendation) 50 W ground transmitter power (Typically power for HPOL) Omni-directional antenna Coverage: 23 NM radius GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 11

Service Technique de la Navigation Aérienne GBAS ground segment III - VDB message content • The current SARPS require the transmission of three message types : – Differential Code Corrections and integrity Data – Reference Point and GBAS Data – Final Approach Path description GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 12

Service Technique de la Navigation Aérienne GBAS ground segment IV - GBAS Ground System Classification • The global performances of Ground System are linked to : – the Number of installed GNSS receivers (2 to 4) – The quality of the GNSS signal reception • A Ground Accuracy Designator (GAD) will qualified the ground segment GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 13

Service Technique de la Navigation Aérienne GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 14

Service Technique de la Navigation Aérienne GBAS User segment I-Basic operations • GBAS will be basically used as an ILS (ILS Look-alike concept) • RNAV 2 D operations may be developed if the Ground System support the Positioning Service GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 15

Service Technique de la Navigation Aérienne GBAS User segment II-Airborne Equipment • Multi-mode Receivers (MMR) and their associated GPS and VHF antennas will be used for GBAS approaches • No hardware update is foreseen (Software only) GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 16

Service Technique de la Navigation Aérienne Conclusions • • The GBAS system as standardised in ICAO Annex 10 is able to serve Cat-I operations. Advanced operations such as Cat-II/III or A-SMGCS are under consideration by ICAO GNSS Panel GBAS ground stations – are being built, – are considered in several implementation programmes in the World • GBAS airborne equipment – are being developed within Multi-Mode Receiver – are considered in several aircraft manufacturer programmes • Standards Status – ICAO Standards (SARPS) are available – Other Standards (Doc 4444, Doc 8071, PANS OPS) are being finalised – Industry Standards (MOPS) are being developed and will be soon available GBAS OVERVIEW CAR/SAM ATN/GNSS Seminar Page 17