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My question is please explain why the meridional parts for 1degree N/S is 59.6 and for 10 degrees N/S is 599 and not 60 and 600 or greater as a simple soul as myself might have assumed?  Not until 11.5 degrees N/S do the meridional parts start to exceed the degrees of latitude x 60.   Is this a quirk of the full meridional parts formula; because the earth is an ellipsoid not a sphere; or because Mercator or a subsequent developer decided to have two small circles of contact rather than one great circle of contact a bit like a Lamberts Conical projection has two small circles of contact causing the scale between to be slightly compressed?  Dave