Bearing calculates the initial and final angles (in degrees) taken on the route (P, Q) using Great Circle navigation.

Haversine uses the haversine formula to return a great-circle distance between two latitude/longitude points.

Returns the distance between two points (given by lat and long coordinates) in meters.

isInPath determines whether the location via which we are going through is in the cone formed by the current position and the destination.

Precalculated angles to speed up the process.