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George also wrote:

> Calculating difference of longitude, using meridional parts, gets
> imprecise for rhumb-line courses very near to 90 or 270 degrees, due
> East or West, and becomes impossible if the course is exactly East or
> West. The problem is that with such courses, the difference of
> latitude (and so the difference of Meridional Parts) approaches zero,
> which is compensated for by the way (tan course) increases towards
> infinity for courses near due East and West. So the result is a
> decreasing precision, for courses near East and West, and an
> meaninglessness, multiplying zero by infinity, for due East and West.

Fascinating. Let's see how Meridional Parts and Distances handles this.

Q3) We're off again, heading due west this time (TC 270d) over 2751nm from
S11d 33.8'  E153d 14.7'. Just where will we end up?

A3) S11d 33.8'  E106d 31.2.

Is there a problem with this, I wonder? Incidentally, taking a Great Circle
route would have saved a comparatively trivial 7nm or so at that low
latitude.

Hey, I've thought of a neat way of checking the accuracy of the method:

Q4) We start from a nice round set of numbers: N/S 0d  E/W 0d. We go east
for 21638.9nm. Where do we arrive?

This time I won't supply my answer just yet. Will look forward to seeing
YOUR solution, ladies and gentlemen - with workings; methodology attached,
please.

Frank, you're barred until you supply the answer to your earlier puzzle
posed about the latitude that gets the most sun.

   

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