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RE :
http://www.fer3.com/arc/m2.aspx?i=115502
[NavList] Lat and Long by moon transit.
From: Anabasis75---com
Date: 28 Jan 2011 11:06

Hello Jeremy,

Thanks a LOT for providing us with a Moon LAN example.

Provided that I have entered all numbers correctly (33 !!! shots are quite unusual, even for a former "Sextanthollah" like Kermit), here are the results I am getting :

Observed Moon Transit (i.e. Moon "crossing" Moving Observer's Meridian, due South of Observer actually) happened at UT = 09h51m39.7s (LT = 18h51m39.7s)
LAN Observed Position at this time was : N+21°49'5 E-130°03'7,
Standard Deviation of Observations was 0.6 NMN, which translates into :
Standard deviation on Latitude 0.6 NM (same value as above given great number of Observations) and SDEV for Longitude = 1.9'

Observed Culmination Time was UT = 09h51m42.6s, only 2.9s apart from Transit time. Since the Ship south speed (-13'15 / hour) was almost the same as the Moon Declination south speed (-12.86' /hour), "the displacement [was actually] somewhat minimized" as you also indicated.

Dead Reckoning our 09h51m39.7s LAN position into a position for 10:00:00 UT / 19:00:00 LT which was the time of your GPS Fix, we get :

CelNav Observed Position at 19:00:00 LT = N21°47'6 , E-130°03'2
to be compared with GPS Position for same instant at : N21°48'7 E130°07'5

Overall Moon LAN Fix accuracy :

in Latitude : 1.1 NM ( not quite 2 times Latitude SDEV), and
in Longitude : 4.3' ( 2.3 times Longitude SDEV)

Last Note : From my results printed listing I just checked (only one time though ...) my typed data which all seem correct (over 450 individual digits typed). Therefore the results I am deriving should be based on data correctly entered.

Best Regards and Thanks again for your Contribution

Kermit

Antoine M. "Kermit" Couëtte

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