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

Use

RYA Marcq St Hilaire

• Reliable two book method Nautical Almanac +NP303/ AP3270

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

• Others

Texas Instruments Ti T89

$379

Texas Instrument

Ti Voyager 200

$429

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

1000Z1206Z1500Z

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?