Overview of Astro Methods

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Overview of Astro Methods

• Roy Malkin
• STCW95 Master
• FNO, RYA Yachtmaster Ocean

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Methods

• Latitudes by Sun or Polaris
• Longitude by Chronometer
• Older time based methods
• Sumner New Navigation late 19th Century
• Marcq St Hilaire (méthode du point rapproché)
  Intercept Method dominant method

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MCA Marcq St Hilaire

• Davis Method using Cosine Haversine Formula and
  Nories
• Adapted since the 70s to Cosine Method using
  Scientific Calculator

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RYA Marcq St Hilaire

• Reliable two book method Nautical Almanac NP303/
  AP3270

Use
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RN Marcq St Hilaire

• Short PC method using NAVPAC

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RN Fallbacks

• Marcq St Hilaire using NP401 6 Volumes and
  Nautical Almanac or NP303/AP3270 or Cosine

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Marcq St Hilaire Using NA

• Nautical Almanac has own Sight reduction table
• And instructions for programming programmable
  calculator or computer.

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Marcq St Hilaire Calculators

• Star Pilot Software
• Others

Texas Instruments Ti T89 379
Texas Instrument Ti Voyager 200 429
Casio Graph 25 NAVASTRO In French Euros 100
Tamaya PDA Type Calculator with built in
GPS Euros 990
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PC Programmes

• Commercial 25 - 129
• Free Ware www.celnav.de

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Apps for Tablets
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• USNO
• Instant Solution to PZX Triangle
• Any Location
• Any Nav Body
• Free with Internet Access

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Nautical Almanac App
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Marcq St Hilaire

• Solution to 19th Century Problem
• Rapid Sights solution to limited mathematical
  capability
• Advent of computers and high speed calculation
  should cause a reassessment of Astro Problem
• No need to solve PZX triangle
• True direct calculation now possible
• But for accuracy Great Circle Distances must be
  calculated for the Geoid
• http//www.ngs.noaa.gov/PC_PROD/Inv_Fwd/

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Position of the Sun on WECDIS
1000Z
1206Z
1500Z
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WECDIS Direct Plot of morning TZD
TZD 47º 38.6 2258.6 NM
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WECDIS Direct Plot noon TZD
TZD 37º 22.3 1642.3 NM Lat 50º 49.1
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WECDIS Direct Plot afternoon TZD
TZD 43º 09.5 2589.5 NM
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WECDIS Zoom in for Plot of Fix
1500Z Obs
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Astro Navigation Solutions for the Future

• What is Astro?
• Precision Navigation (WGS 84/Vincenty) ?
• Landfall Ocean Crossing system?
• Regular check system to GPS?
• Final Emergency System?
• Or a redundant system frozen in time?