NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Longitude from Local Apparent Noon Altitudes
From: Bruce J. Pennino
Date: 2012 Aug 19, 20:50 -0400
From: Bruce J. Pennino
Date: 2012 Aug 19, 20:50 -0400
Hello:
If you look at an aerial of Provincetown ,MA, Snail Road leaves Rt 6 and goes toward bay. Snail Road meets 6A. I was just 300-400 ft east of there standing on a sun bathing deck adjacent to the water.Actually, the deck overhangs the beach/water at high tide. This location is directly north of the point you determined.
From "eyeballing data" and folding graph, I guesstimated UT of 16h43m56sec.
Based on an online calculator, the sun deck location is N 42 04' W 070 10'. Your analysis...very well done!
My "analysis" gave me N 42 06 W 70 00.......learning!
Thanks all
Bruce
On Sun, Aug 19, 2012 at 3:27 PM, =?utf-8?Q?Antoine Cou=C3=ABtte?= wrote:
Hello Bruce,
Provided I understood everything correctly (I figured out that the first UT was 16h22m02.2s and so on ....) and provided I correctly entered all ... 325 numbers on my Calculator - while knowing that just one single typo can ruin all the results - I found the following results (7th order regression) :
UT of Transit (i.e. body full south of Observer's Position) 16h44m12,8 , hence a Longitude of W070°04'3 ,
UT of Culmination occurred 8,23s earlier, i.e. at UT = 16h44m04s6 . The 8.23s difference between both comes from the Sun Declination which is decreasing. In this case, a first order value for the time difference in seconds of time is (48/Pi)* Declination change in arc minutes per hour.
I assummed that the Observer is steady on Earth.
Observed latitude N42°02'3 S
Standard Deviation of the Observations : 0.9 NM (defines quality of Observations)
Longitude Uncertainty / Latitude uncertainty (both in arc minutes) <= 3.9
In other words, the Latitude should be accurate to +/- 2.7 NM at 3 Sigma, and the Longitude should be accurate to +/- 10'5 at 3 Sigma, as long as I have correctly entered the 64 different values for these 32 Observations.
Best Regards to all
Kermit
----------------------------------------------------------------
NavList message boards and member settings: www.fer3.com/NavList
Members may optionally receive posts by email.
To cancel email delivery, send a message to NoMail[at]fer3.com
----------------------------------------------------------------
