# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: lat/long from meridian passage
From: Patrick Goold
Date: 2011 Jan 24, 13:12 -0500
Dear Antoine,
Thanks!  I appreciate seeing your numbers.  I will try this again the next time the sun comes out, taking three sets of paired sights and keeping them well before and after the max. alt.   What Jim has me puzzling about now is how you would employ this method on a moving vessel.

Best regards,
Patrick

On Mon, Jan 24, 2011 at 2:33 AM, Antoine Couette wrote:

RE : http://www.fer3.com/arc/m2.aspx?i=115413
[NavList] lat/long from meridian passage
From: goold---edu
Date: 22 Jan 2011 20:43

Dear Patrick,

From your own data, summarized as follows :

22 Jan 2011 (TT-UT=67.2 s) SUN Local Apparent Noon
Fixed Position T=-4�C, P=1013.25 mb/Hpa = 29.92", Height of Eye = 0 ft
All Heights "H" herebelow are "as would be observed in the Sextant and corrected for only instrument error",

1 - UT=17h00m00.0s H=33�08'0
2 - UT=17h15m00.0S H=33�18'0
3 - UT=17h17m00.0s H=33�17'8
4 - UT=17h19m23.0s H=33�18'0
5 - UT=17h34m20.0s H=33�08'0

Without knowing your position I derive the following results :

SUN transit, i.e. "crossing" the Observer's Meridian happened at Time UT = 17h17m00.3s

Observer's Position : N36�49'3 W076�21'9
Standard deviation of your 5 data set : 0.7 NM
Uncertainty in Longitude (1 Sigma) = 2'6

EXCELLENT LUCK for your first Local Apparent Noon Observation. Your CelNav Observed Position falls quite close (0.7 NM !!!) from your actual GPS position recorded as N36�50'0 W076�21'7

Also - and as just recently noted too by Jeremy - Latitude determination is generally (very) much better than Longitude determination when performing LAN's Observations, a fact which has long been recognized. See in particular "Calculator Navigator" by M. Mortimer Rogoff.

Best Regards

Antoine

Antoine M. "Kermit" Cou�tte

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--
Dr. Patrick Goold
Department of Philosophy
Virginia Wesleyan College
Norfolk, VA 23502
757 455 3357

Charles Olson: "Love the World -- and stay inside it."

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