NavList:

John said:

You talked about my plane graph paper chart and finding your AP and the longitude of the fix.  I may have been doing things wrong all these years but I take a UPS or graph paper and draw a X in the middle and that is my AP.  The North - South scale is NM ( or tenth of NM ), use a protractor to draw my Azimuth and then draw the LOP so many NM from my AP.  Where the LOPs cross I note how many NM north or south and east or west.  For north-south I just say that NMs are minutes of arc and add that to my AP.  For east-west I multiply by cos(lat) and call the result degrees of arc and add that result to my AP.

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-Your method works when you can plot all of your LOPs from one assumed position using a calculator or HO214 or HO 211, or Bygrave computor, or HO 249 volume 1 with MOB and MOO adjustments, or any other method that allows computing from a DR or known position. I think everybody on navlist has taken observations from a known position in order to practice with his sextant, obtaining the known position with GPS, since this allows evaluating the quality of the sextant work. So you end up with a fix that is plotted in relation to the AP and you take out the north component and add it to your assumed latitute and then you see the distance to east or west and convert that distance to difference in longitude by using the secant of the latitude (either from your calculator or, HORRORS! from a trig table, remember those) just like you did. You can also do this convenienly on your E-6B, see attached pages from AFM 51-40.

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Over the years I seem to  get accurate results.  I do not draw any other mederians on the plotting sheet because I never saw what good they would do.  I never thought I was drawing a map ( chart ) and I know I could not use my piece of paper to go anywhere - it only gave me a Lat & Long of my fix.

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Yep, no reason to drawing in those other meridians unless you need the comfort of seeing what looks like your standard chart. You can still plot positions by taking out longitudes from the angled line which provides the secants used to construct the plotting sheet and this is exactly what the naval aviators did on the Mk3 and on the Mk 6 plotting boards.

gl

gl