NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2024 Dec 22, 17:24 -0800
Lars wrote
for a latitude of 10°, I get the meridional parts equal 603.070' for the sphere. Are you sure that the Smithsonian document from 1909 and Norie from 1918 really shows 603.7'?
My mistake. Should be 603.07 for the sphere and 599.01 for the 1/293.465 spheroid. According to Inman the reduction is 4' (at 10° lat) and 11' 44" (at 45° lat) for the Clarke (1880) spheroid.
Would there have ever been a situation where for practical navigation the reduction mattered? Did practical navigators ever worry (or understand) the Clarke spheroid? When calculating a mercator sailing it is the difference of meridional parts (dmp) that matters. At all latitudes the reductions are of the same sign so the dmp correction will always be less than 11'.
In the navigation tables there seemed to be little consistancy in which flattening (if any) was used.
David C
