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Download Displaying Astro Position Lines
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Transcript
Overview of Astro Methods Roy Malkin STCW95 Master FNO, RYA Yachtmaster Ocean 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 MCA Marcq St Hilaire • Davis Method using Cosine Haversine Formula and Nories • Adapted since the 70s to Cosine Method using Scientific Calculator RYA Marcq St Hilaire • Reliable two book method Nautical Almanac +NP303/ AP3270 Use RN Marcq St Hilaire • Short PC method using NAVPAC RN Fallbacks • Marcq St Hilaire using NP401 6 Volumes and Nautical Almanac or NP303/AP3270 or Cosine Marcq St Hilaire Using NA • Nautical Almanac has own Sight reduction table • And instructions for programming programmable calculator or computer. Marcq St Hilaire Calculators • Star Pilot Software Texas Instrument Texas Instruments Ti T89 Ti Voyager 200 $379 $429 • Others Tamaya PDA Type Calculator with built in GPS Euros 990 Casio Graph 25+ NAVASTRO In French Euros 100 PC Programmes • Commercial $25 - $129 • Free Ware www.celnav.de Apps for Tablets • USNO • Instant Solution to PZX Triangle • Any Location • Any Nav Body • Free with Internet Access Nautical Almanac App 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/ Position of the Sun on WECDIS 1500Z 1206Z 1000Z WECDIS Direct Plot of morning TZD TZD 47º 38.6’ 2258.6 NM WECDIS Direct Plot noon TZD TZD 37º 22.3’ 1642.3 NM Lat 50º 49.1’ WECDIS Direct Plot afternoon TZD TZD 43º 09.5’ 2589.5 NM WECDIS Zoom in for Plot of Fix 1500Z Obs 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?
