Antipodal Points

Two points are antipodal (i.e., each is the Antipode of the other) if they are diametrically opposite. Examples include endpoints of a Line Segment, or poles of a Sphere. Given a point on a Sphere with Latitude $\delta$ and Longitude $\lambda$, the antipodal point has Latitude $-\delta$ and Longitude $\lambda\pm 180^\circ$ (where the sign is taken so that the result is between $-180^\circ$ and $+180^\circ$).

See also Antipode, Diameter, Great Circle, Sphere