Longitude and latitude of the starting point,
position angle and distance to the final point.
Quantities should be in angular units; floats in radians.
Polar points at lat= +/-90 are treated as limit of +/-(90-epsilon) and same lon.

The position of the final point. If any of the angles are arrays,
these will contain arrays following the appropriate numpy broadcasting rules.
0 <= lon < 2pi.