# 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:**Marcel Tschudin

**Date:**2009 Apr 16, 20:04 +0300

Brad, regarding your comment on the least square fit: "The navigator is urged to, in one case, fair a line thru a series of data points or in another, to visualize a parabola as we slide the paper. That isn't a least squares fit by any stretch of the imagination." It's actually surprising how well we can estimate a linear regression line through data points with a reasonable correlation only by using a ruler. In this case it would only require to adjust the scale of the axis accordingly. Marcel On Thu, Apr 16, 2009 at 6:55 PM, Brad Morriswrote: > > I agree with your result for a least squares fit of the parabola to the measured data. With the variation > limited, there is no doubt that the least squares fit will provide a reasonable parabola and therefore a > fairly good estimation of Lat and Lon. �If this is how the method is used in practice, you will find little > argument from me. > > However neither procedure, as I understand them to date, uses a least squares fit. �The > navigator is urged to, in one case, fair a line thru a series of data points or in another, to visualize > a parabola as we slide the paper. �That isn't a least squares fit by any stretch of the imagination. > As such, we may find that the deviation in longitude is somewhat greater than your value of 5.68nm. > > Best Regards > Brad > > > > > -----Original Message----- > From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of waldendand{at}YAHOO.COM > Sent: Thursday, April 16, 2009 11:23 AM > To: NavList@fer3.com > Subject: [NavList 7970] Re: Lat/Lon by "Noon Sun" & The Noon Fix PROVE IT > > > 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 > > > > > > "Confidentiality and Privilege Notice > The information transmitted by this electronic mail (and any attachments) is being sent by or on behalf of Tactronics; it is intended for the exclusive use of the addressee named above and may constitute information that is privileged or confidential or otherwise legally exempt from disclosure. If you are not the addressee or an employee or agent responsible for delivering this message to same, you are not authorized to retain, read, copy or disseminate this electronic mail (or any attachments) or any part thereof. If you have received this electronic mail (and any attachments) in error, please call us immediately and send written confirmation that same has been deleted from your system. Thank you." > > > > --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To unsubscribe, email NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---