1. EGNOS TRAN: Broadcasting EGNOS messages over the Eurofix Datalink
Gerard Offermans, Arthur Helwig & Durk van Willigen
Reelektronika, the Netherlands

2. 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

3. Why EGNOS TRAN? EGNOS GEO visibility in München EGNOS NOT Visible
EGNOS Visible
From: The GLORIA Project by M. Maurer, ILA-29, Washington, DC.

4. 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

5. 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

6. EGNOS-Eurofix Local Area
EGNOS satellite
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 to Eurofix data conversion & Eurofix transmission control
Including Eurofix to RTCM data conversion
EGNOS Rx calculates RTCM corrections based on reference position and EGNOS data
EGNOS/Eurofix PC unpacks RTCM messages and reformats to standard Eurofix messages
User receives standard Eurofix messages and applies as LAAS correction

7. 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)

8. EGNOS-Eurofix Wide Area
NMEA (position)
EGNOS satellite
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
Thales Rx passes DO-229 EGNOS data on to EGNOS PC
EGNOS PC unpacks EGNOS data and reformats into EGNOS Eurofix messages
User receiver receives Eurofix messages and stores EGNOS data
User receiver calculates optimal correction data based on user position (true wide area)

9. ETRAN Message Types E-TRAN Type Content EGNOS Source Do not use ! 1
Do not use ! 1
Fast corrections, 2 satellites/message
2-5 2
Fast & slow correction, 1 satellite/message 3
Slow correction, 1 satellite/message 25 4
Ionospheric grid 18 5
Ionospheric Grid delay model parameters, 3 IGPs/message 26

10. Wide Area EGNOS TRAN message types
ETRAN type 0 – Do not use data
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)

11. Wide Area EGNOS TRAN message types
ETRAN type 1 – Fast correction (2 satellites/message)
Field
Bits
# bits
Units
Range
Eurofix Type (8)
1-4 4 16
ETRAN Type (1)
5-7 3 8
Satellite ID
8-15
256
Fast correction
16-27 12
0.125 m
-256 – m
UDREI
28-31
0-16
32-39
40-51
52-55
Spare 56 1
CRC
57-70 14
Source: EGNOS message 2,3,4,5 (satellite fast corrections)
EGNOS message 0! (WAAS compatibility mode)

12. 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
256
Fast correction
16-27 12
0.125 m
-256 – m
UDREI
28-31
0-16
IOD
32-39
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)

13. 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
256
IOD
16-23
δaf0
24-32 9
2-31 s
2-23 s δx
33-40
0.250 m
-32 – 32 δy
41-48 δz
49-56
CRC
57-70 14
Source: EGNOS message 25 (satellite slow corrections)

14. 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
Total Subs
10-11
IODI
12-13
0-3
IGP mask bits
14-53 40
Spare
54-56
CRC
57-70 14
Source: EGNOS message 18 (ionospheric grid mask)
Eurofix station coverage area & Gridpoints ‘in view’

15. 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
160
IGP vertical delay estimate
18-26 9
0.125 m m
Grid IVEI
27-30
0-15
31-39
40-43
44-52
53-56
CRC
57-70 14
Source: EGNOS message 26

16. Wide Area EGNOS message distribution
Satellite and Ionospheric corrections are interleaved:
2 Satellite Corrections to 1 Ionospheric Correction
Fast and slow corrections are interleaved (2 to 1)
2 type-1 Fast corrections (2 SVs)
1 type-2 Fast & slow correction
or type-3 Slow 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) 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)

17. Installation at Loran-C station Sylt
250-kW Solid State 100 kHz
200-m Antenna mast

18. Installation at Loran-C station Sylt
Antenna mounts
Equipment Rack
EGNOS 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
Thales
EGNOS
GPS
Antenna
Eurofix
Integrity
Monitor
GPS
Antenna
Eurofix
Datalink
Monitor
Loran-C
Antenna
Eurofix
Reference
Station
GPS
Antenna

19. LORADD EGNOS TRAN Receiver
Get your EGNOS TRAN receiver upgrade today!!! **
‘All-in-view’ Loran-C/Eurofix receiver, tracks all stations
Improved Loran tracking and Eurofix datalink performance through advanced DSP algorithms
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)

20. Measurements Performed by Teleconsult Austria Country Mode
The Netherlands E-TRAN LAAS
Germany E-TRAN LAAS
France E-TRAN LAAS
Sweden E-TRAN RAAS

21. Measurement results - Göteburg

22. Measurement results - Göteburg
ETRAN 100% availability
EGNOS GEO: 100% availability

23. 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

24. Potential European Eurofix coverage …which is about the footprint of EGNOS

25. Polar Routes Restricted Russian polar routes: Polar 1 to 4
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
Restricted Russian polar routes: Polar 1 to 4
Preferred random routing in Canada
2005: 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

26. 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

27. More information http://galileo.cs.telespazio.it/egnostran/
home/files/etran4gis.pdf