GNSS Development Status and Future Work Eric Chatre, EC/ESA Rapporteur Technical WG, GNSS Panel
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Transcript of GNSS Development Status and Future Work Eric Chatre, EC/ESA Rapporteur Technical WG, GNSS Panel
GNSS DevelopmentStatus and Future Work
Eric Chatre, EC/ESA Rapporteur Technical WG, GNSS Panel
Agenda Item 6
Outline
• GNSS Elements
• GNSS Performance Requirements– Definition of parameters
– Relationship betweens parameters
• Integrity Principles
• GNSS Standards
• Future Work
GNSS Elements
GPS GLONASS
Core Constellations
Augmentations
ABAS
SBAS
GBAS
IOR
Aircraft-Based Augmentation System (ABAS)
• Stand-alone technique implemented in user equipment/software
• No accuracy improvement, lateral guidance only
• Provides integrity based on consistency check• Needs redundant satellite measurements (5
or more satellites in view with good geometry)• Integrity only• Performance and availability limited to some
phases of flight
Satellite-Based Augmentation System (SBAS)
• Objectives –Improve accuracy of GPS or GLONASS by
providing corrections for • Satellite errors : clock and ephemeris • Ionospheric errors : model over a geographic area
–Provide integrity information–Lateral and vertical guidance–Improved availability,
Satellite-Based Augmentation System (SBAS) (cont.)
• Architecture– Network of stations covering a wide area (e.g.
continent)– Transmission of information to users through
geostationary satellites
• Coverage and Service areas– Coverage : Wherever the geostationary
signals are received– Service : Wherever operations have been
approved by States
SBAS Architecture
Reference Reference StationsStations
Master StationMaster Station
Uplink Uplink StationStation
GEOGEO
GPSGPS
SBASSBASMessageMessage
Ground-Based Augmentation System (GBAS)
• Objectives –Improve accuracy of GPS or GLONASS
by providing for each satellite a composite correction
• Satellite errors : clock, ephemeris correction valid locally
• Ionospheric errors : local correction• Tropospheric errors : local correction
–Provide integrity information
Ground-Based Augmentation System (GBAS)(cont.)
• Architecture– Ground Reference Station (typically 1 per
airport) – Transmission of information to users through
a VHF data link (108 to 118 MHz)
• Coverage – Approach area (ILS like coverage)– Terminal area (positioning service)
GBAS Architecture
GPS and/or GLONASS, GEOs
User
Reference station and VDB
VHF DATA LINK
Aviation Performance Requirements for GNSS (signal-in-space)
Phase of
Flight
Accuracy
(95%)
Integrity Risk Continuity Risk
Availability
En Route H: 3.7 Km
1x10-7/h 1x10-4/h to 1x10-8/h
0.99 to 0.99999
Terminal H: 0.74 Km
NPA H: 220 m
APV I H: 16 m
V: 20 m
2x10-7/App 8x10-6/ 15sAPV II H: 16 m
V: 8m
Cat I H: 16 m
V: 6 to 4 m
Cat II/III
Surface Ops
Under Development
Interpretation of parameters
Accuracy : Characterize typical behavior of the system in presence of nominal error components
Integrity : Limit risk of abnormal behaviour of the system due to errors resulting from system failures
-Integrity Risk-Alert Limit-Time to Alert
Continuity : Limit risk of losing the service unexpectedly
Availability : Accuracy + Integrity [+ Continuity]
Relationship between parameters
Integrity
Accuracy
Continuity
Availability
•Availabilty
-Vertical accuracy/integrity is usually the main driver
-Decreases as accuracy increases
-Decreases as alert limit gets smaller
•GNSS performance is variable :- in time- in space
-New approach to ensure integrity for all users
-Protection Level concept
Integrity principles
Alert Limit
Computed Position
User Computed Protection Level
Protection Level > Alert Limit Alert
Protection Level < Alert Limit No Alert
Probability 1-1.10-7
GNSS Standards, Procedures, Guidance Material
• Standards and Recommended Practices (ICAO Annex 10, Vol I)
• GNSS NOTAMS and Phraseology (ICAO Annex 15, PANS-ABC Doc 8400, PANS- ATM Doc 4444)
• Procedure Design Criteria (PANS-OPS, Doc 8168)• Geodetic Reference Datum and Data Base Requirements
(ICAO Annexes 4,11,14 &15, WGS-84 Manual Doc 9674) • Information and guidance on implementation (GNSS Manual)• Industry Standards (RTCA and EUROCAE MOPS/MASPS)
Industry Standards
• The main actors are :– RTCA in the US, Special Committee 159– EUROCAE in Europe, Working Group 28
• The Documents – Minimum Operational Performance Specifications (MOPS)– Minimum Aviation System Performance Standards (MASPS)
• Existing Standards– ABAS/Basic GNSS receiver : DO-208 / ED-72 / (J)TSO-C129A– SBAS receiver : DO-229 C / TSO-145A/146A– GBAS Cat I receiver : DO-253A– Multi-Mode Receiver including GBAS : ED-88A
Future Work
• Evolution of currently standardized GNSS elements• GPS modernization with additional civil signal on L5
frequency (1176.45 MHz)• GLONASS modernization (GLONASS K) with additional
civil signal in the 1164-1215 MHz band• Extention of SBAS standards to accomodate new
signals• Extention of GBAS standards to accomodate new
signals and cover Category II/III and surface operations
Future Work (cont.)
• New GNSS elements• GALILEO system with 3 civil signals and a
dedicated integrity service• Ground-Based Regional Augmentation System
(GRAS)