Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Latitude and longitude around noon
    From: Bill Ritchie
    Date: 2017 Mar 11, 17:43 +1300

    Sean, you made me look at Greg’s photographs closely. I thought the vessel was a laden tanker, but is it not the barge RTC 145 with attendant tug Christian Reinauer pushing at the stern? If so, at present (1700 on 11th March New Zealand Time) she is berthed at Sewaren, New Jersey which (unless she can do over 40 knots) rules out my Cape Horn alternative position! But wait, she appears to be carrying deck cargo just forward of the crane – or is that a distant island?



    Bill Ritchie


    On Sat, Mar 11, 2017 at 2:18 PM, Sean C <NoReply_SeanC@fer3.com> wrote:

    I thought I'd give it a go while we're waiting for the answer. I put the middle three altitudes into excel seeing as how the 4th and 6th were almost equal. I then enabled a polynomial trendline and arrived at a LAN time of 16:59:09 and a max altitude of 41°30.3'. I used these as a starting point and input the resulting lat/lon into StarPilot-89 (which I had received as a Christmas gift from my wife). So, starting with a "DR" of 41°27.4' N, 71°46.7' W, I asked StarPilot for a fix by computation. The result was 41°27.2' N, 71°27.3' W. Next, I used the "Sight Analyzer" at the given fix to see how the curve fit.

    StarPilot's sight analyzer works by calculating the Hc for each time at the fix and subtracting out the corrections to arrive at "Hs'". It then plots a curve (or slope) corresponding to the motion the body should have been exhibiting at the given times and location. The user can then slide the curve up or down to account for random/systematic error and find the best fit. The method is a lot like the one described by David Burch in his paper at the Starpath website. Anyway, the curve looked pretty good right off the bat. So I am going with StarPilot's calculation of 41°27.2' N, 71°27.3' W. The intercepts at this location are 0.0', +0.9', -0.5', -0.6', +0.6', -0.2', -0.1', +0.4', +0.2' and 0.0' respectively. (µ = 0.07', σ = 0.4') See attached screen shots.

    [Actually, taking Frank's pictures into account, I would say a longitude of 71°23.7' W is more likely. But, I think that's kind of cheating, so I'll go with the previous location.]

    Cheers,

    Sean C.



    Attached File:



    Attached File:



    Attached File:




    File:


       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site