NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lat/Lon by "Noon Sun" & The Noon Fix PROVE IT
From: Dave Walden
Date: 2009 Apr 16, 08:23 -0700
From: Dave Walden
Date: 2009 Apr 16, 08:23 -0700
The .doc file works great. Thanks. I took George's spreadsheet and automated it with a macro. First, I used it to generate 1000 sets of 13 observations. For each set, I let excel fit the parabola, and find the time and altitude of its peak. I then find the difference between the resulting latitude and longitude thus calculated and the true values. Thus for each set of 1000, I get a mean and standard deviation of the error. Using George's convenient "scatter switches", I tried various combinations. He has four switches. In order, the first turns on/off the scatter in ship speed (if one always uses the nominal 10 knots in the calculation), the second changes the equation of time (as I understand it, changing the value to be calculated as opposed to introducing scatter into the result), the third changes the longitude (same comment), the fourth adds scatter to the observed altitude. In the table below, the switches are listed in order, 1=on, 0=off. As can be seen for everything on, the standard deviation of longitude error in nm is 5.68. It can be seen the ship speed scatter seems to have a slightly greater effect than the altitude reading scatter. The 1 mile lat and 5 mile long estimates look pretty good to me. YMMV. 1,1,1,1 min lat min long nm long mean 0.00 0.19 0.11 stdev 0.40 10.16 5.68 max 1.29 48.02 26.85 0 1 1 1 mean 0.01 0.19 0.10 stdev 0.44 6.57 3.67 max 1.55 22.64 12.66 0 0 1 1 mean 0.00 -1.00 -0.56 stdev 0.42 6.73 3.77 max 1.41 20.77 11.61 0 0 0 1 mean -0.01 -0.38 -0.21 stdev 0.44 6.72 3.76 max 1.14 20.50 11.46 1 1 1 0 mean 0.00 -0.22 -0.12 stdev 0.05 7.48 4.18 max 0.25 24.18 13.52 0 1 1 0 mean -0.01 -0.38 -0.21 stdev 0.00 0.01 0.01 max 0.00 -0.34 -0.19 1 0 0 1 mean 0.01 0.17 0.09 stdev 0.42 9.97 5.58 max 1.33 32.45 18.14 --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---