Overview of Performance Analysis of Alternative Navigation

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Overview of Performance Analysis of Alternative
Navigation

• Sherman Lo, Rick Niles

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Outline

• Performance Study
• Parameterized study allows study of many
  architectures and equipment performance
• Rick will show some first cut test
• Integrity Study

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Performance Requirements for Alternate Nav

• Coverage/Performance study only one part
• Test to most stringent performance level
  (operation supported)
• Availability/coverage/accuracy
• Other performance issues
• Integrity/TTA security
• Update rate, continuity, etc.

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Summary of architecture alternatives
Technique Characteristic Tx for horiz. Position Addl Req.
Two way, aircraft based DME DME-P/enhanced DME 2 2
One way, aircraft based Pseudolite/heartbeat, DME/TDOA (DME-Loran) 3 3 Gnd clock sync
Hybrid, aircraft based Pseudolite/heartbeat, DME/TDOA (DME-Loran) 2 2 Gnd clock sync
Two way, ground based Active MLAT (reverse DME) 2
One way, ground based Passive MLAT (reverse heartbeat) 3 Gnd clock sync
Hybrid, ground based Active/Passive MLAT 2 Gnd clock sync
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What can we simplify and why Example
Time removed from solution Time part of solution
Ground Based DME DME-P DME heartbeat (with 2 way time) Pseudolite DME heartbeat
Aircraft Based Active MLAT Passive MLAT

• Each column should have similar coverage
  (geometry)
• Similarities due to geometry, number of
  measurements needed for solution
• Assuming same ground stations used
• Difference due to error on each measurement,
  measurement time difference (if TDMA)
• Accuracy will differ
• Implementation may differ greatly even though
  concepts similar

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Test Scenario Matrix

• Performance in US (highlighting 50-150 busiest
  airports)
• Altitude 350 ft AGL (RNP 0.3) and at altitude
• Ground infrastructure
• 1. DME stations
• 2. MLAT stations
• 3. Both
• 1-3 plus a few additions, depending on results
  above
• Solve for horizontal position with passive or
  active ( hybrid) concepts
• Passive needs 3 stations (need to resolve user
  clock error)
• Active needs 2 stations (assuming ambiguity can
  be resolved)
• Accuracy start by calculating DOP
• Gets a rough idea of required performance of
  ground infrastructure
• Doesnt cover all cases (i.e. range dependent
  accuracy, different accuracy between GBT, DME)
• RAIM/Integrity Calculate residual matrix
• Proposal Ben and I will work on a reasonable
  quantity

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Simplified Test Matrix
Infrastructure/ accuracy DME Only MLAT Only DME MLAT
DOP (for 2 D, no clock sync) Coverage RNP 0.3, altitude
DOP (for 2 D, clock sync)

• Test matrix for either passive or active/hybrid
• Full matrix in example represents 12 different
  tests
• Can reduce number of cases
• May not need to consider coverage at 350 ft for
  some cases
• Not necessarily final design gets us some idea
  of performance
• DOP is not adequate if accuracy vary (due to
  distance, GBT may differ from DME)

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Accuracy

• Parameterized by ranging accuracy
• Ranging accuracy determined by
• Equipment performance
• Concept of operations (CONOPS)
• Ex. Simultaneous or serial measurements
• Range dependent errors (propagation, SNR)
• Rough approximation for s s(d), or different s
  for different ground transmitters
• Similar idea for RAIM integrity
• Use nominal accuracy and minimum detectable error

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DME Accuracy

• DME/N
• System accuracy of 0.17 NM (up to 200 NM range)
  (ICAO Annex 10, as referenced by ION paper)
• sair MAX(0.085 nm, .00125d), ssis 0.05 nm,
  (AC90-100A)
• DME/P accuracy changes with distance from runway
• 15 m to 250 m (centerline) (position domain)
  (ICAO Annex 10)

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MITRE Coverage tool for DME/GBT

• Rick Niles will discuss