ILA 32 – 4-7 November 2003 1 Gerard Offermans - reelektronika
EGNOS TRAN: Broadcasting EGNOS messages over the
Eurofix Datalink
Gerard Offermans, Arthur Helwig & Durk van Willigen
Reelektronika, the Netherlands
ILA 32 – 4-7 November 2003 2 Gerard Offermans - reelektronika
What is EGNOS?
• EGNOS = European WAAS
• Differential Corrections and Integrity for GPS
• Ground network of RIMS measure satellite range errors
• Range errors are spit into ionospheric component and satellite specific errors
• Broadcast of Wide-Area data via Geostationary Satellites
• All based on RTCA DO-229B documentation
ILA 32 – 4-7 November 2003 3 Gerard Offermans - reelektronika
Why EGNOS TRAN?
From: The GLORIA Project by M. Maurer, ILA-29, Washington, DC.
EGNOS GEO visibility in München
EGNOS Visible
EGNOS NOT Visible
ILA 32 – 4-7 November 2003 4 Gerard Offermans - reelektronika
EGNOS TRAN solution
• Eurofix datachannel capacity appr. 30 bps
• EGNOS bandwidth 250 bps
EGNOS TRAN solution
• EGNOS TRAN does not back-up GEO datalink
• EGNOS TRAN backs-up EGNOS functionality
ILA 32 – 4-7 November 2003 5 Gerard Offermans - reelektronika
EGNOS TRAN Local Area solution
• EGNOS receiver outputs RTCM SC104 LAAS correction data for all satellites in view of Loran Transmitter
• Eurofix Station converts this message to a standard Eurofix message
• User gets Local Area correction – Input into standard GPS receivers– Suffers from Spatial Decorrelation
ILA 32 – 4-7 November 2003 6 Gerard Offermans - reelektronika
EGNOS-Eurofix Local Area
EGNOS Rx calculates RTCM corrections based on reference position and EGNOS dataEGNOS/Eurofix PC unpacks RTCM messages and reformats to standard Eurofix messagesUser receives standard Eurofix messages and applies as LAAS correction
Thales EGNOS RX
EGNOS PC
250 kW Loran-C TX
RTCM
DGPS RX Eurofix RX
Eurofix data
Loran-C pulses
Loran-C TX
DGPS user position
H-field Loran-C Antenna
GPS Antenna
RTCM
RTCM to Eurofix data conversion & Eurofix transmission control
Including Eurofix to RTCM data conversion
EGNOS satellite
ILA 32 – 4-7 November 2003 7 Gerard Offermans - reelektronika
EGNOS TRAN Wide Area solution
• EGNOS receiver provides “raw” EGNOS data• Eurofix Station extracts information and reduces
dataset• Eurofix Station reformats information into E-
TRAN Eurofix message• User calculates ionospheric delay and satellite
clock errors for all satellites based on estimated User position– Pure Wide Area solution– No spatial decorrelation– Requires position feedback to the Eurofix receiver
(GPS or Loran-C)
ILA 32 – 4-7 November 2003 8 Gerard Offermans - reelektronika
EGNOS-Eurofix Wide Area
Thales Rx passes DO-229 EGNOS data on to EGNOS PCEGNOS PC unpacks EGNOS data and reformats into EGNOS Eurofix messagesUser receiver receives Eurofix messages and stores EGNOS dataUser receiver calculates optimal correction data based on user position (true wide area)
Thales EGNOS RX
EGNOS PC
250 kW Loran-C TX
EGNOS format
DGPS RX Eurofix RX
Eurofix data
Loran-C pulses
Loran-C TX
DGPS user position
H-field Loran-C Antenna
GPS Antenna
RTCM
EGNOS to Eurofix data conversion & Eurofix transmission control
Including EGNOS Eurofix to RTCM data
conversion
NMEA (position)
EGNOS satellite
ILA 32 – 4-7 November 2003 9 Gerard Offermans - reelektronika
ETRAN Message Types
E-TRAN Type
ContentEGNOS Source
0 Do not use ! 0
1 Fast corrections, 2 satellites/message 2-5
2 Fast & slow correction, 1 satellite/message 2-5 + 25
3 Slow correction, 1 satellite/message 25
4 Ionospheric grid 18
5Ionospheric Grid delay model parameters, 3 IGPs/message
26
ILA 32 – 4-7 November 2003 10 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (0) 5-7 3 8
Body (all zeroes) 8-56 49
CRC 57-70 14
Source: EGNOS message 0! (WAAS compatibility mode)
ETRAN type 0 – Do not use data
ILA 32 – 4-7 November 2003 11 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (1) 5-7 3 8
Satellite ID 8-15 8 256
Fast correction 16-27 12 0.125 m -256 – 255.875 m
UDREI 28-31 4 0-16
Satellite ID 32-39 8 256
Fast correction 40-51 12 0.125 m -256 – 255.875 m
UDREI 52-55 4 0-16
Spare 56 1
CRC 57-70 14
ETRAN type 1 – Fast correction (2 satellites/message)
Source: EGNOS message 2,3,4,5 (satellite fast corrections) EGNOS message 0! (WAAS compatibility mode)
ILA 32 – 4-7 November 2003 12 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
ETRAN type 2 – Fast & Slow correction (1 sattellite/message)
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (2) 5-7 3 8
Satellite ID 8-15 8 256
Fast correction 16-27 12 0.125 m -256 – 255.875 m
UDREI 28-31 4 0-16
IOD 32-39 8 256
δaf0 40-50 11 2-31 s 2-21 s
Spare 51-56 6
CRC 57-70 14
Source: EGNOS message 2,3,4,5,0 (satellite fast corrections) EGNOS message 25 (satellite slow corrections)
ILA 32 – 4-7 November 2003 13 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
ETRAN type 3 – Slow correction (1 satellite/message)
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (3) 5-7 3 8
Satellite ID 8-15 8 256
IOD 16-23 8 256
δaf0 24-32 9 2-31 s 2-23 s
δx 33-40 8 0.250 m -32 – 32
δy 41-48 8 0.250 m -32 – 32
δz 49-56 8 0.250 m -32 – 32
CRC 57-70 14
Source: EGNOS message 25 (satellite slow corrections)
ILA 32 – 4-7 November 2003 14 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
ETRAN type 4 – Ionospheric Grid
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (4) 5-7 3 8
Grid Sub ID 8-9 2 4
Total Subs 10-11 2 4
IODI 12-13 2 0-3
IGP mask bits 14-53 40
Spare 54-56 3
CRC 57-70 14
Source: EGNOS message 18 (ionospheric grid mask)Eurofix station coverage area & Gridpoints ‘in view’
ILA 32 – 4-7 November 2003 15 Gerard Offermans - reelektronika
Wide Area EGNOS TRAN message types
ETRAN type 5 – Ionospheric Grid delay model parameters (3 IGPs/message)
Field Bits # bits Units Range
Eurofix Type (8) 1-4 4 16
ETRAN Type (5) 5-7 3 8
IODI 8-9 2 0-3
First Grid point 10-17 8 160
IGP vertical delay estimate 18-26 9 0.125 m 0-63.875 m
Grid IVEI 27-30 4 0-15
IGP vertical delay estimate 31-39 9 0.125 m 0-63.875 m
Grid IVEI 40-43 4 0-15
IGP vertical delay estimate 44-52 9 0.125 m 0-63.875 m
Grid IVEI 53-56 4 0-15
CRC 57-70 14
Source: EGNOS message 26
ILA 32 – 4-7 November 2003 16 Gerard Offermans - reelektronika
Wide Area EGNOS message distribution
Fast and slow corrections are interleaved (2 to 1)
2 type-1 Fast corrections (2 SVs)
1 type-2 Fast & slow correctionor type-3 Slow correction
Satellite and Ionospheric corrections are interleaved: 2 Satellite Corrections to 1 Ionospheric Correction
Grid and IGP data messages are interleaved (1 to 7)
1 type-4 Ionospheric grid
7 type-5 IGP data (3 IGPs)
In total 113 IGP points for Sylt area, so a whole transmission sequence is:
3 type-4 messages (grid) + 38 type-5 messages (IGP data) interleaved 2 to 1
Approximately 123 (=3 times 41) messages before all (IGP) data is acquired
Sylt update rate is one message every 2 seconds (single rate)
EGNOS TRAN Cold start acquisition time 246 seconds (4 minutes)
ILA 32 – 4-7 November 2003 17 Gerard Offermans - reelektronika
Installation at Loran-C station Sylt
200-m Antenna mast
250-kW Solid State transmitter @ 100 kHz
ILA 32 – 4-7 November 2003 18 Gerard Offermans - reelektronika
Installation at Loran-C station SyltEGNOS TRAN equipment
← Thales EGNOS Rx
← Modem & power supply
← EGNOS TRAN PC
Existing Eurofix installation
← Eurofix Rx & power supply
← 2x GPS Rx & Modem
← CPU switch
← Integrity Monitor PC
← Reference Station PC
← UPS
Equipment RackAntenna mounts
ThalesEGNOS
GPSAntenna
EurofixIntegrityMonitor
GPSAntenna
EurofixReference
StationGPS
Antenna
EurofixDatalinkMonitorLoran-CAntenna
ILA 32 – 4-7 November 2003 19 Gerard Offermans - reelektronika
LORADD EGNOS TRAN Receiver
• ‘All-in-view’ Loran-C/Eurofix receiver, tracks all stations• Improved Loran tracking and Eurofix datalink performance through
advanced DSP algorithms
**
Get your EGNOS TRAN receiver upgrade today!!!
• Modified to perform User Differential Correction calculations based on received EGNOS TRAN messages
• Used in trials with EGNOS TRAN on 6731Z and Eurofix on 7499M (Sylt)
ILA 32 – 4-7 November 2003 20 Gerard Offermans - reelektronika
Measurements
• Performed by Teleconsult Austria
Country Mode– The Netherlands E-TRAN LAAS– Germany E-TRAN LAAS– France E-TRAN LAAS– Sweden E-TRAN RAAS
ILA 32 – 4-7 November 2003 21 Gerard Offermans - reelektronika
Measurement results - Göteburg
ILA 32 – 4-7 November 2003 22 Gerard Offermans - reelektronika
Measurement results - Göteburg
ETRAN 100% availabilityEGNOS GEO: 100% availability
ILA 32 – 4-7 November 2003 23 Gerard Offermans - reelektronika
Measurement results
• EGNOS TRAN Datalink performed well, even in areas where GEO is unavailable
• Generally, where GEO and EGNOS TRAN via Eurofix are available, the DGPS performance is similar
• E-TRAN Local Area mode is less accurate than E-TRAN Wide Area mode (spatial decorrelation)
• Proven EGNOS functionality back-up using “low bit-rate” data channel
ILA 32 – 4-7 November 2003 24 Gerard Offermans - reelektronika
Potential European
Eurofix coverage
…which is about the
footprint of EGNOS
ILA 32 – 4-7 November 2003 25 Gerard Offermans - reelektronika
Polar Routes
• Restricted Russian polar routes: Polar 1 to 4
• Preferred random routing in Canada
• 2005: 9000+ commercial polar flights estimated
• Savings:– Flying time: 2+ hrs– Costs: US$ 16
k/flight– Time slots Atlantic
• ‘Polar Routes Feasibility Study’, Nav Canada and FAAR, October 2000
4970M+5960Z 1,200 kW
4970X+5960Y 250 kW
5960X 1,200 kW
7001Y 250 kW
7270X+5930Z 800 kW
7960M 560 kW
9990Y+7960Z 1,000 kW
7001X+9007W 250 kW
9990Y+7960Z 1,000 kW
ILA 32 – 4-7 November 2003 26 Gerard Offermans - reelektronika
Conclusions
• ETRAN exceeds SBAS availability in cities, forests and mountainous environment
• Loran-C navigation function very dissimilar backup for GPS outages
• Loran-C TX modification low-cost, especially if station has access to WAAS or EGNOS data networks
• Can be implemented on Eurofix in Europe as well as on Loran-Comm in the US
• E-TRAN Data update can easily be improved by using dual-rate and multiple stations
ILA 32 – 4-7 November 2003 27 Gerard Offermans - reelektronika
More information
• http://galileo.cs.telespazio.it/egnostran/
• http://galileo.cs.telespazio.it/egnostran/home/files/etran4gis.pdf