Antipodal points are two points on Earth that are diametrically opposite
to each other.
How to calculate an antipodal point?
Latitude: Negate the original latitude (-lat)
Longitude: Add or subtract 180° from the original longitude, then
normalize to -180° to 180° range.
If longitude is greater than 180°, subtract 360° If longitude is
less than -180°, add 360°.