A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Andrés Ruiz
Date: 2012 Oct 24, 17:45 +0200
The deviation between a true, constantly curved great circle course and a straight line approximation will be far less than your measurement uncertainty, especially for a running fix whose total duration is less than one hour.
In other words, I would not worry about it and just assume a straight line course, instead of a curved course.