'radius of curvature of the latitude circle in the plane of the circle
'
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'radius of the sphere
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'angle from the pole to the latitude circle at the center of the sphere
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'line of sight distance between the pole and a point on the latitude circle, i.e. the length of the sagitta
'
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'distance from the pole to a point on the latitude circle measured along the surface of the sphere
(2)
where'
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'the radius of curvature of the latitude circle as a driver on this circle would have to steer. At the equator this radius is infinte, i.e. the curvature of the equator latitude circle is 0 for a driver following this great circle.
'
='
'radius of curvature of the latitude circle in the plane of the circle
'
='
'angle from the pole to the latitude circle at the center of the sphere