NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Multi-Moon line exercise in 2 parts
From: Peter Hakel
Date: 2009 Aug 7, 20:50 -0700
From: "Anabasis75@aol.com" <Anabasis75@aol.com>
To: NavList@fer3.com
Sent: Tuesday, August 4, 2009 8:33:54 PM
Subject: [NavList 9359] Multi-Moon line exercise in 2 parts
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From: Peter Hakel
Date: 2009 Aug 7, 20:50 -0700
Jeremy,
I processed your away-from-transit data in the following manner:
1) Using your 1800 DR position as the AP, I calculated the intercepts and azimuths for all 30 moonlines (see the attached file rapid_in.txt).
2) I advanced or retarded all moonlines to UT = 09:00:00 = 1800L.
3) I calculated running fixes using all possible pairs of LOP's. From them I extracted average values of latitude and longitude and their standard deviations (see the attached program rapid.f90).
The term "rapid-fire fix" I borrowed from Frank Reed, although I do not know whether this is the way it's normally done.
This way I get for the 1800L fix:
Latitude: N 22 degrees 02.2' ; standard deviation = 13.3'
Longitude: E 130 degrees 14.6' ; standard deviation = 46.1'
An important detail is that I obtained this result by disregarding the second measurement (at 8:54:46) because its intercept does not seem to "belong" among all the others (it is AWAY, while all others are TOWARD). If I do include this outlier, the results get worse:
Latitude: N 21 degrees 58.0' ; standard deviation = 39.7'
Longitude: E 130 degrees 01.7' ; standard deviation = 110.5' (almost 2 degrees...)
Peter Hakel
I processed your away-from-transit data in the following manner:
1) Using your 1800 DR position as the AP, I calculated the intercepts and azimuths for all 30 moonlines (see the attached file rapid_in.txt).
2) I advanced or retarded all moonlines to UT = 09:00:00 = 1800L.
3) I calculated running fixes using all possible pairs of LOP's. From them I extracted average values of latitude and longitude and their standard deviations (see the attached program rapid.f90).
The term "rapid-fire fix" I borrowed from Frank Reed, although I do not know whether this is the way it's normally done.
This way I get for the 1800L fix:
Latitude: N 22 degrees 02.2' ; standard deviation = 13.3'
Longitude: E 130 degrees 14.6' ; standard deviation = 46.1'
An important detail is that I obtained this result by disregarding the second measurement (at 8:54:46) because its intercept does not seem to "belong" among all the others (it is AWAY, while all others are TOWARD). If I do include this outlier, the results get worse:
Latitude: N 21 degrees 58.0' ; standard deviation = 39.7'
Longitude: E 130 degrees 01.7' ; standard deviation = 110.5' (almost 2 degrees...)
Peter Hakel
From: "Anabasis75@aol.com" <Anabasis75@aol.com>
To: NavList@fer3.com
Sent: Tuesday, August 4, 2009 8:33:54 PM
Subject: [NavList 9359] Multi-Moon line exercise in 2 parts
I figured that I need to give some LOP data to reduce with all of
these people building and using their Bygrave's slide rules, and to stir the pot
a bit on the list. So in order to kill two birds with one stone, I offer
the attached Excel spreadsheet. Lying therein are a plethora of upper limb
moon LOP's which should allow eager navigators to fix the position of my
ship. There are a few features of particular note that should appeal to
certain members of the list.
1) The given DR is a real DR tracked from the AM star fix some 14
hours earlier
2) The moon is fairly close to the celestial equator (please note the LARGE
hourly change in declination)
3) The ship's track is at a fair clip and nearly Southerly.
These should be considered fairly extreme conditions to work out the
Latitude and Longitude of the ship; the first position from many LOP's away
from upper transit, and then again around the time of transit.
I will be most appreciative if people who solve the transit portion
graphically can post an image or file of their curve and to see what the
1900L fixes is. (ZD -9)
I offer the following challenges:
1) what would you calculate the local zone time of transit to
be?
2) what was the 1800L fix?
3) what was the 1900L fix?
4) what was the actual local zone time of transit by observation?
5) most critically, how much faith would you put in these fixes?
I will post the actual GPS fixes and my celestial solutions for both
times at a later time.
Have fun!
Jeremy
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