page 1 gbas overview car/sam atn/gnss seminar service technique de la navigation aérienne ground...

GBAS OVERVIEW GBAS OVERVIEW CAR/SAM ATN/GNSS SeminarCAR/SAM ATN/GNSS Seminar

Service Technique de la Navigation Aérienne

GROUND BASED AUGMENTATION SYSTEMGROUND BASED AUGMENTATION SYSTEMSystem OverviewSystem OverviewChristophe DEHAYNAIN

Direction Générale de l’Aviation Civile FRANCE

GROUND BASED AUGMENTATION SYSTEMGROUND BASED AUGMENTATION SYSTEMSystem OverviewSystem OverviewChristophe DEHAYNAIN

Direction Générale de l’Aviation Civile FRANCE



GROUND BASED AUGMENTATION SYSTEMGROUND BASED AUGMENTATION SYSTEM

Presentation Presentation OverviewOverview

GROUND BASED AUGMENTATION SYSTEMGROUND BASED AUGMENTATION SYSTEM

Presentation Presentation OverviewOverview

• Why do we need an augmentation to GNSS ?

• Local Area Differential GNSS Principle

• GBAS Ground Segment

• GBAS Airborne Segment

• Conclusions

• Why do we need an augmentation to GNSS ?

• Local Area Differential GNSS Principle

• GBAS Ground Segment

• GBAS Airborne Segment

• Conclusions



GBAS ConceptGBAS Concept

SystemSystem Overview Overview

GBAS ConceptGBAS Concept

SystemSystem Overview 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 kHz spacing)

• Operational objective : – minimum : Category 1 approach– optional : 2 D navigation (Positioning Service)

• Localisation : Airport

• 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 kHz spacing)

• Operational objective : – minimum : Category 1 approach– optional : 2 D navigation (Positioning Service)

• Localisation : Airport



GBAS OverviewGBAS Overview

Do not mistake Do not mistake GBASGBAS for : for :GBAS OverviewGBAS Overview

Do not mistake Do not mistake GBASGBAS for : for :

• DGPS, LADGPS : initial US generic names for GBAS concept

• SCAT1 or Special Category 1 : US RTCA standard defining a non-interoperable system for private use

• LAAS : Local Area Augmentation System : present US name for GBAS

• DGPS, LADGPS : initial US generic names for GBAS concept

• SCAT1 or Special Category 1 : US RTCA standard defining a non-interoperable system for private use

• LAAS : Local Area Augmentation System : present US name for GBAS



WHY GNSS NEEDS AN AUGMENTATION ?WHY GNSS NEEDS AN AUGMENTATION ?WHY GNSS NEEDS AN AUGMENTATION ?WHY GNSS NEEDS AN AUGMENTATION ?

PERFORMANCE CATEGORY IRequirements

ACCURACY (95%)

INTEGRITY

AVAILABILITY

H. 13 m V. 23 m V 4.0 mH 16.0 m

99.75 %

3,5.10-7/ approachTime to alarm 6 s

99% (RAIM)

GPS Only Civil Aviation

CONTINUITY OF SERVICE 10-4 / approach(10-5 / 15 s)

?

?



LOCAL AREA DIFFERENTIAL PRINCIPLELOCAL AREA DIFFERENTIAL PRINCIPLEI - Basic PrincipleI - Basic Principle

LOCAL AREA DIFFERENTIAL PRINCIPLELOCAL AREA DIFFERENTIAL PRINCIPLEI - Basic PrincipleI - 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

• Measurements made by two receivers are affected by the same errors as long as these two receivers are not too far from each other

RX1

RX2



LOCAL AREA DIFFERENTIAL PRINCIPLELOCAL AREA DIFFERENTIAL PRINCIPLEII - Differential Correction CalculationII - Differential Correction Calculation

LOCAL AREA DIFFERENTIAL PRINCIPLELOCAL AREA DIFFERENTIAL PRINCIPLEII - Differential Correction CalculationII - Differential Correction Calculation

– The first receiver in a reference station can 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

– The first receiver in a reference station can 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

REFUSER

Known Reference Location

Calculated Range

Actual SV Position

Broadcast SV Position

CorrectionsCalculation Differential Message Broadcast

Measured Pseudoranges



GBAS ground segmentGBAS ground segmentI - BI - Basic architecture of a reference stationasic architecture of a reference station

GBAS ground segmentGBAS ground segmentI - BI - Basic architecture of a reference stationasic architecture of a reference station

Receiving Unit(up to 4 Reference Receivers)

Data Processing Unit

Data Broadcast Unit

Raw DataPR, ephem.,time

• Differential Corrections Calculation• Integrity Monitoring Functions• GBAS Messages Elaboration

Data processing for

broadcast

GPS/GLONASS Antennas Differential Message Broadcast Antenna



GBAS ground segmentGBAS ground segmentII - II - VHF Data Broadcast (VDB)VHF Data Broadcast (VDB)

GBAS ground segmentGBAS ground segmentII - II - VHF Data Broadcast (VDB)VHF Data Broadcast (VDB)

• GBAS VDB characteristics : – VHF NAV band (108 - 118 MHz), channel spacing 25 kHz

– D8PSK (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)– 50W ground transmitter power (Typically power for HPOL)– Omni-directional antenna– Coverage: 23 NM radius

• GBAS VDB characteristics : – VHF NAV band (108 - 118 MHz), channel spacing 25 kHz

– D8PSK (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)– 50W ground transmitter power (Typically power for HPOL)– Omni-directional antenna– Coverage: 23 NM radius



GBAS ground segmentGBAS ground segmentIII - III - VDB message contentVDB message content

GBAS ground segmentGBAS ground segmentIII - III - VDB message contentVDB 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

• 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 ground segmentGBAS ground segmentIV - GBAS Ground System ClassificationIV - GBAS Ground System Classification

GBAS ground segmentGBAS ground segmentIV - GBAS Ground System ClassificationIV - 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

• 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 User segmentGBAS User segmentI-Basic operationsI-Basic operations

GBAS User segmentGBAS User segmentI-Basic operationsI-Basic operations

• GBAS will be basically used as an ILS (ILS Look-alike concept)

• RNAV 2D operations may be developed if the Ground System support the Positioning Service

• GBAS will be basically used as an ILS (ILS Look-alike concept)

• RNAV 2D operations may be developed if the Ground System support the Positioning Service



GBAS User segmentGBAS User segmentII-Airborne EquipmentII-Airborne Equipment

GBAS User segmentGBAS User segmentII-Airborne EquipmentII-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)

• Multi-mode Receivers (MMR) and their associated GPS and VHF antennas will be used for GBAS approaches

• No hardware update is foreseen (Software only)



ConclusionsConclusionsConclusionsConclusions

• 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

• 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

page 1 gbas overview car/sam atn/gnss seminar service technique de la navigation aérienne ground...

Documents

gbas slide

gbas dgps

gbas ground station

gbas concept scat1

navigation arienne slide

local area augmentation

airport slide

psk differential