EGNOS TRAN: Broadcasting EGNOS messages over the Eurofix Datalink

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. Loran-C pulses Eurofix data Loran-C TX RTCM 250 kW Loran-C TX Thales EGNOS RX EGNOS PC H-field Loran-C Antenna RTCM to Eurofix data conversion & Eurofix transmission control RTCM DGPS RX Eurofix RX GPS Antenna Including Eurofix to RTCM data conversion DGPS user position EGNOS-Eurofix Local Area EGNOS satellite • 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 satellite NMEA (position) Loran-C pulses Eurofix data Loran-C TX EGNOS format 250 kW Loran-C TX Thales EGNOS RX EGNOS PC H-field Loran-C Antenna EGNOS to Eurofix data conversion & Eurofix transmission control RTCM DGPS RX Eurofix RX GPS Antenna Including EGNOS Eurofix to RTCM data conversion DGPS user position EGNOS-Eurofix Wide Area • 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

10. Wide Area EGNOS TRAN message types ETRAN type 0 – Do not use data Source: EGNOS message 0! (WAAS compatibility mode)

11. Wide Area EGNOS TRAN message types ETRAN type 1 – Fast correction (2 satellites/message) 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) 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) Source: EGNOS message 25 (satellite slow corrections)

14. Wide Area EGNOS TRAN message types ETRAN type 4 – Ionospheric Grid 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) Source: EGNOS message 26

16. 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 Satellite and Ionospheric corrections are interleaved: 2 Satellite Corrections to 1 Ionospheric Correction Wide Area EGNOS message distribution 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)

17. Installation at Loran-C station Sylt 250-kW Solid State transmitter @ 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. LORADDEGNOS 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)

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. 9990Y+7960Z 1,000 kW 7960M 560 kW 9990Y+7960Z 1,000 kW 5960X 1,200 kW 4970X+5960Y 250 kW 7001Y 250 kW 4970M+5960Z 1,200 kW 7270X+5930Z 800 kW 7001X+9007W 250 kW 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

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/ • http://galileo.cs.telespazio.it/egnostran/home/files/etran4gis.pdf • G.Offermans@reelektronika.nl