On Thu, 09 Oct 2008 13:27:55 -0400, Wayne.B
wrote:

On Thu, 9 Oct 2008 09:01:39 -0700 (PDT), "
wrote:

That might work as a piece-wise approximation.

Sorry, I know that wasn't a very helpful idea. Since a straight line
on a gnomic chart is a great circle if you just count the number of
degrees along the line that should provide naut miles. I'm not sure
how helpful dividers would be in measuring those degrees. I'm also
not sure if they make gnomic charts to a scale appropriate for
plotting such short distances. What would be the point?

Good question since it's so easy to do it computationally. Our
friend Richard Casady claimed he could do it with dividers but I
suspect he hasn't really tried it. The only graphical solution with
dividers that I would have much faith in would be on the surface of a
globe using a taut string. Everything else I can think of would be a
piece-wise approximation using computed way points on a Mercator
chart.

You can't possibly think the difference between a 6 mi long rhumb line
and a great circle is of any significant. My uncle navigated a few
million miles with dividers and charts. I have the dividers, two of
them, as a matter of fact. The E6B nav computer has circular slide
rule on one side, on the other a slice of a plotting board, for
solving wind triangles. I have that one, and another he stole and gave
me in 64. There was a sextant built into the plane. You ever hear of a
B-52 getting lost?

Casady