Satellite Based Augmentation
Systems - SBAS
Lecturer:
Michael O'Grady
Course:
MSc Ubiquitous & Multimedia Systems
Unit:
Context Sensitive Service Delivery
Lecture:
SBAS
Objectives
 Outline current developments in
Satellite Based Augmentation Systems
(SBASs)
Satellite - Current Developments
Global Navigation Satellite System (GNSS)
• Aims to resolve the conflict between civilian and military
demands
• seeks to provide position readings to within 3 metres
Two phases
 GNSS-1
• Resolves most technical issues
• Political issues still remains
• Introduces Satellite Based Augmentation Systems
(SBASs)
 GNSS-2
• Seeks to provide a global infrastructure for positioning
and timing
GNSS-1 - EGNOS
European Geostationary Navigation
Overlay System (EGNOS)
 Developed by
• European Commission
• Eurocontrol
• European Space Agency
 Coverage area includes
• all Europe, Africa and the Middle East
• parts of Asia and South America
 Uses INMARSAT-3 satellites for broadcasting
correctional and integrity data
 Scheduled for launch in 2006
GNSS-1 - WAAS
Wide Area Augmentation System (WAAS)
 Designed by the Federal Aviation Authority
(FAA)
 Designed to provide precise navigational
services to aircraft for the duration of flight
 Network of 25 ground stations spread across
the USA
 INMARSAT-3 used to broadcast connections
• same frequency as GPS signal
• Receiver must be WAAS enabled
• Currently being deployed
GNSS-1 - LAAS
Local Area Augmentation System (LAAS)
 intended to operate when WAAS cannot
•I.e when visibility is less than 1 km
 Deployed in the immediate vicinity of airports
 Will only broadcast data to aircraft in sight of
the corresponding ground reference station
GNSS-1 - MSAS
Multifunctional Transport Satellite
Augmentation System (MSAS)
 Services include
Navigation
Meteorology
 Architecture
• 24 ground stations
• 2 satellites
 Features
• Area covered include most Asia/Pacific air space
• Compatible with EGNOS and WAAS
• Developed solely by Japan
GNSS – Developments
India
GAGAN
China
SNAS
Canada
CWAAS
EGNOS - Services
GEO Ranging
GPS-like signals
GMSS Integrity Channel
Signal integrity information
Wide Area Differential (WAD)
Differential corrections
EGNOS - ARCHITECTURE
Four Segments
Space
Ground
User
Support Facilities
EGNOS Diagram
EGNOS – Space Segment
Three Geostationary transponders
INMARSAT-3 AOR-E
INMARSAT-3 AOR-W
ESA ARTEMIS
EGNOS Ground Segment - RIMS
Ranging and Integrity Monitoring Stations
(RIMS)
GPS, GLONASS, EGNOS(!)
34 stations (mainly in Europe)
• GPS/GLONASS/EGNOS receiver
• Atomic clock
• Network access
RIMS tasks
Pseudorange measurements
Demodulate SIS messages
Mitigate multipath & interference
Verify signal integrity
Packet & transmit data to MCC
EGNOS Ground Segment - MCC
Mission/Master Control Centre (MCC)
• 4 stations in Europe
• Monitoring & control of EGNOS
• Real-time software processing
MCC tasks
•
•
•
•
Integrity determination
Pseudo-range corrections for each satellite
Ionospheric delay
Generate Satellite (EGNOS) ephemeris
EGNOS Ground Segment - NLES
Navigation Land Earth Station (NLES)
Two for each satellite (EGNOS)
• 1 primary
• 1 backup
One for Test & Validation
NLES Tasks
•
•
•
•
Generate GPS-like signal
Generate GIC signal (GNSS Integrity Channel)
Generate Wide Area Differential (WAD) signal
Transmit signals to GEO (EGNOS)
EGNOS Ground Segment - EWAN
EGNOS Wide Area Network
Links all EGNOS ground-based components
EGNOS – User Segment
EGNOS Receiver
Uses
Civil Aviation
Land
Marine
EGNOS – Support Facilities
Support for
Development
Operations
Verifications
SISNet
Signal In Space over the Internet
(SISNet)
Provides EGNOS signal over standard
TCP/IP connection
User Requirements
PDA/mobile phone
Wireless data connection e.g. GPRS
GPS card/receiver
Why SISNet?
Recall …
 Geostationary orbits
 Low elevation angles
So…………
Consider
 In urban canyon?
 At high latitudes?
References
ESA WWW site
EGNOS
SISNet
SpringerLink
GPS Solutions