Spherical world utilities
The default value of the radius is Earth's radius of 6378137 meters.
Heading expressed as degrees between locations expressed as
distance(from, to, [radius])
Distance in meters between locations expressed as
radial(from, heading, distance, [radius])
Given a location as
[lon, lat], heading in degrees, and distance in meters,
[lon, lat] point of a point at that offset.
Adapted from OpenLayers