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Thanks to Lars of 59N 18E for directing more light on this topic, especially
for explaining why the two sets of tables I have display different factors.
And to Andres Ruis for his contribution a little earlier, although I have
understood but little of his formidable formulas.

As to the original question of whether the method using both Meridional
Parts and Distances is more accurate than a calculation using Meridional
Parts alone, it would seem (at the moment) to depend on the precise
circumference of the globe at the equator. To the extent that this is indeed
21638.9nm then the method is entirely accurate. Since the route is also a
Great Circle those calculations serve as a check method. My calculations
show a discrepancy of 00d 00.1', or about 185 metres.

In practice the method using both Meridional Parts and Distances is the only
competitor in this two horse race if the calculation using Meridional Parts
(alone) is incapable of providing a solution for courses due east or west.

Of course the method should be equally valid for traverses along any
bearing. Can anyone think of an objective test of accuracy for these random
bearing traverses?

Circumference of the globe at the equator:

24901.55 miles (40075.16 km) according to
www.infoplease.com/ipa/A0908193.html

40075.16/1852 = 21,638.855

Looking good - if this data is correct.

   

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