EGNOS TRAN: Broadcasting EGNOS messages over the Eurofix Datalink

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EGNOS TRAN Broadcasting EGNOS messages over the
Eurofix Datalink

• Gerard Offermans, Arthur Helwig Durk van
  Willigen
• Reelektronika, the Netherlands

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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

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

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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

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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

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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)

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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)

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ETRAN Message Types
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Wide Area EGNOS TRAN message types
ETRAN type 0 Do not use data
Source EGNOS message 0! (WAAS compatibility
mode)
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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)
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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)
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Wide Area EGNOS TRAN message types
ETRAN type 3 Slow correction (1
satellite/message)
Source EGNOS message 25 (satellite slow
corrections)
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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
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Wide Area EGNOS TRAN message types
ETRAN type 5 Ionospheric Grid delay model
parameters (3 IGPs/message)
Source EGNOS message 26
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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) 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)
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Installation at Loran-C station Sylt
250-kW Solid State transmitter _at_ 100 kHz
200-m Antenna mast
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Installation at Loran-C station Sylt
Equipment Rack
Antenna mounts
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 Reference Station GPS Antenna
Eurofix Datalink Monitor Loran-C Antenna
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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)

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Measurements

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

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Measurement results - Göteburg
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Measurement results - Göteburg
ETRAN 100 availability EGNOS GEO 100
availability
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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

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Potential European Eurofix coveragewhich is
about the footprint of EGNOS
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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

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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

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More information

• http//galileo.cs.telespazio.it/egnostran/
• http//galileo.cs.telespazio.it/egnostran/home/fi
  les/etran4gis.pdf
• G.Offermans_at_reelektronika.nl