# NavList:

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

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Re: Pointless? Optimisation - Intercept Plotting
Date: 2019 Feb 1, 19:02 -0500
Hi Michael

That looks pretty clever.  I want to be sure I understand the steps and what you are doing.

Step 1) Reduce observation, obtaining azimuth, and intercept distance (T/A).
2) Rotate base of protractor to observation azimuth, making sure T or A of protractor bow is in the orientation you want.
3) Align compass rose of protractor.  N[orth] arrow, such that is co-incident with N/S meridian.
4) Then: "Shimmy it about until the EP is the intercept distance from the bow edge" and mark your LOP across the bow edge.

Do I have your method properly laid out?  I understand using the lines at the "bow" to measure your T/A distance.  That is pretty clever and represents an interesting shortcut.

There is a dilemma for me at step 4 however.  I cannot understand how you keep the angular orientation of the bow of the protractor constant while "shimmying" it about. A small angular error can yield a large error in fix, if the angle between intercepts is small.

One way to maintain angle would be to set parallel rules across the bow of the protractor.  Then pin one side of the parallel rules, moving the other side, such that the intercept distance is indicated by your "bow lines".  It uses every part of what you have suggested, but maintains the angle!

Still no extraneous marks.  Still no divider pin pricks.

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