Bearing when a Point P is above the Ellipsoid of Revolution ORS

• This is an edge view of the tangent plane (purple) and the normal plane (red) at A

• A and B are on the ORS (B is below the horizon)

• The green and blue arrows represent the normals NA and NB

• This is the defining geometry for bearing angle

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• In this case, the normal plane is rotated to the point P

• A and B are on the ORS (B is below the horizon)

• The green and blue arrows represent the normals NA and NB

• This does not define the same bearing angle

• Mathematical adjustments need to be made to compute bearing – this process is called “reduction”