Satellite-Based Augmentation Systems (SBAS) Combined Performance

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Satellite-Based Augmentation Systems (SBAS)
Combined Performance

• International Committee on GNSS (ICG-4)
• Working Group A
• Saint Petersburg, Russia
• 15 September 2009
• Frederic Bastide, European Commission
• Ken Alexander, United States
• Analysis by MITRE Center for Advanced Aviation
  System Development

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Purpose

• Describe combined SBAS performance for
  single-frequency SBAS capable civil receivers
• Develop performance maps for existing SBAS
  services
• Establish methodology for illustrating
  performance for future evolutions of SBAS

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Introduction

• The United States of America and the European
  Union are jointly working on the development of
  estimates of availability of worldwide aviation
  navigation service using SBASs that will be
  operational in the 2010 timeframe.
• WAAS
• MSAS
• EGNOS
• The work is conducted in cooperation between the
  US Federal Aviation Administration (FAA), The
  European Commission (EC) and the European Space
  Agency (ESA).
• GPS-only availability will also be estimated for
  comparison
• This briefing shows illustrative examples and
  describes planned analyses
• This work is intended to be shared in a
  multi-lateral environment

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Scope of Simulation

• SBAS worldwide navigation services availability
  estimated using systems planed for 2010
  operations
• Wide Area Augmentation System (WAAS)
• Multi-functional Satellite Augmentation System
  (MSAS)
• European Geostationary Navigation Overlay Service
  (EGNOS)
• GPS unaugmented availability provided for
  comparison
• Current results are based on GPS L1 C/A for
  aviation Required Navigation Performance (RNP)
  services including Lateral Precision with
  Vertical Guidance (LPV)
• Opportunity to address GPS-aided Geo Augmented
  Navigation (GAGAN) and System of Differential
  Correction and Monitoring (SDCM) as follow-on
  activity

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Assumptions

• Global map representation
• Service Levels RPN 0.3 and RNP 0.15 Nautical
  Miles
• Compares GPS, SBAS/GPS during periods when two
  primary slot GPS satellites are out of service
• GPS constellation
• Specific days identified in 2008
• User equipment
• User equipment compliant with the minimum
  performance standards as described in RTCA
  DO-229D
• SBAS
• Considers latest configurations (EGNOS, MSAS and
  WAAS)
• Services are determined by number of factors,
  including number and location of reference
  stations, actual system design details, and
  environmental conditions

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Constellation Assumptions

• April 29, 2008, from 1014Z to 1214Z (GMT)
• 29 satellites operating, not including
• PRN 2 (D1 plane/slot)
• PRN 30 (B2 plane/slot)
• June 7, 2008, from 1751Z to 2005Z (GMT)
• 28 satellites operating, not including
• PRN 9 (A1 plane/slot)
• PRN 25 (A5 plane/slot) not in primary orbital
  slot
• The following slides are examples of information
  these and future analyses can provide
• Improvement brought by SBAS in the case of close
  to nominal 24-sat GPS constellation would be even
  higher

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Observed SBAS Availability

Localizer Performance with Vertical Guidance
(LPV)
Courtesy FAA Technical Center
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RNP 0.3 Availability - Using GPS RAIM (7 June
2008 from 1751Z to 2005Z)

• Parameters
• Horizontal Alert Limit 0.3 nautical miles (NM)
• Availability of GPS Receiver Autonomous Integrity
  Monitoring (RAIM) Fault Detection (FD) function
• Legacy user equipment with 5? mask angle

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RNP 0.3 Availability Using SBAS(7 June 2008
from 1751Z to 2005Z)

• Parameters
• Horizontal Alert Limit 0.3 nautical miles (NM)
• SBAS user equipment with 5? mask angle
• EGNOS v2.2, MSAS Phase 2, WAAS Release 8/9.2

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RNP 0.15 Availability - Using GPS RAIM (29 April
2008 from 1014Z to 1214Z)

• Parameters
• Horizontal Alert Limit 0.15 nautical miles (NM)
• Availability of GPS Receiver Autonomous Integrity
  Monitoring (RAIM) Fault Detection (FD) function
• Legacy user equipment with 5? mask angle

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RNP 0.15 Availability - Using SBAS(29 April 2008
from 1014Z to 1214Z)

• Parameters
• Horizontal Alert Limit 0.15 nautical miles (nm)
• SBAS user equipment with 5? mask angle
• EGNOS v2.2, MSAS Phase 2, WAAS Release 8/9.2

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Future Cases for Consideration

• Availability for other phases of flight
  including
• RNP1 / RNP0.5
• Localizer Performance with Vertical Guidance
  (LPV)
• LPV-200
• Availability when GPS constellation is at minimum
  SPS Performance levels
• Random or specific satellite outages
• SBAS availability when GAGAN and SDCM are
  operational
• Availability of modernized (dual-frequency) SBAS
  augmenting GPS broadcasting two civil signals
• Availability of combined SBAS-augmented GPS plus
  Galileo

Similar to Approach with Vertical Guidance
(APV) Type I (HAL 40m - VAL 50m) LPV down
to 200 ft Height Above Threshold (HAL 40m - VAL
35 m) HAL Horizontal Alert Limit VAL
Vertical Alert Limit
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Conclusion

• Several SBAS systems are either already available
  or planned to be commissioned in the near to mid
  term
• Such systems provide high safety standards and
  very robust navigation services even under
  depleted core constellation scenarios
• The combined service area of SBAS systems is
  significant and should grow in the future as more
  systems are being deployed and as improvements
  are brought to existing systems
• Communicating on the combined performance of
  existing SBAS systems is seen as an important
  aspect to get full benefit of deployed
  infrastructure
• Work is on-going between the SBAS service
  providers to establish SBAS performance levels on
  a global basis.
• Presently Includes Data from WAAS, MSAS and EGNOS
• Plan to Include GAGAN and other regional systems
  data when available
• The EU and the USA are committed to work in this
  direction and bring further information at
  subsequent UN-ICG meetings

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• Questions?

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• Backup

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ICAO Global Mapping Assumptions

• Simulation Assumptions
• User equipment (UE)
• GPS/RAIM UE assuming 100m accuracy (Most legacy
  GPS avionics are of this type)
• GPS/RAIM UE with barometric aiding and GPS SPS
  Performance Standard accuracy
• SBAS UE compliant with DO-229D
• 5-degree elevation masks for all UEs (Except for
  one map for HAL 0.3, which will use a 2-degree
  elevation mask for comparison)
• Weighted RAIM solutions for all UEs
• SBAS
• WAAS and MSAS with GEO ranging
• EGNOS without GEO ranging
• MT 27 or 28 as applicable

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ICAO Global Mapping Assumptions

• Simulation Assumptions
• GPS Constellation
• 24 Satellite Nominal
• 28 Satellite constellation that existed on some
  day in the past year that approximates the
  average constellation observed over the time
  period (short satellite outages that may have
  occurred on that day can be ignored by the
  simulation)
• User locations
• Every 2 degrees of latitude (up to 70N and down
  to 70S) and longitude
• Sampling
• 24 hours sampled every 5 minutes (288 epochs)