Distance on a Spherical ERM
• The blue curve is a small circle arc generated by the intersection of a plane, that does not contain O, with the sphere.
• The red curve is a great circle arc generated by the intersection of a plane, containing O, with the sphere.
• The great circle arc is the minimum distance path on the surface of a sphere.
• The length of the great circle arc can be computed using spherical trigonometry which involves trigonometric functions.
• The normals at A & B are coplanar.
• When an environmental model is added, e. g., terrain, minimum distance paths on a sphere are almost never great circle arcs.