A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: John D. Howard
Date: 2015 Aug 19, 08:37 -0700
I think the confusion is not the difference between astronomical longitude and geodetic longitude but WHERE DID YOU START MEASURING.
If you start the geodetic longitude at Greenwitch then 360 degrees later would it not end at Greenwitch? It seems like the GPS system started at some other physical location and when it came to England it was off. So I ask, Where did the Geodetic longitude start? I cannot imagine that when the folks working on GPS said " I think we should start 100 m from Greenwitch."