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Re: Mercator Sailing and Meridional Parts
From: Paul Hirose
Date: 2014 Dec 02, 09:06 -0800
From: Paul Hirose
Date: 2014 Dec 02, 09:06 -0800
On 2014-11-30 12:31, David Pike wrote: > > Having now discovered Meridional Parts, I’m a bit flummoxed to understand why the ones in Nories Tables* for the Terrestrial Spheroid* come to less than latitude x 60 from 0 degrees to 11.5 degrees before they start racing ahead. Is this because of the compression of 1/293.465 whatever that means? Yes, I think you have the right idea. Imagine a cross section of a grotesquely oblate Earth. Near the equator, the small radius of curvature makes parallels of geodetic latitude crowd together. They're much closer than the meridians of longitude. As you move away from the equator, the convergence of meridians and increasing distance between parallels combine to overpower this effect. That's what you're seeing, though in milder form since the true flattening is only about 1/300. If meridional parts are computed with flattening increased to 1/200, they don't exceed (60 * latitude) until latitude is 14°.
