Surveying on a Spherical ERS

• The blue curve is a small circle arc generated by the intersection of a plane,

with the sphere, that does not contain O

• 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 that 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

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