A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Murray Peake
Date: 2020 Feb 8, 00:52 -0800
That's correct - the effect is more pronounced at higher latitudes. The idea was to allow the navigator to plot the distance run and course directly on the altitude charts. The non-linear latitude spacing is clearer in the example for 1945, Latitude 50 to 60 North, that I posted in 2017.
Example 2 in the 1940 edition (epoch 1945) is for an aircraft, speed 240 knots, course 60 degrees true, 3 min 30 sec between observations.
The 1940 edition had LST in arc rather than time (for convenient use with the Air Almanac) at the foot of the page, and an explanation and examples for the Royal Air Force on the last page.
Were the Weems Curves actually used by the RAF? The copy I have has an insert page with a table of GHA Aries for 1962. The editions seem to have been published in 1928, 1938 and 1940 (for 1945).