module Geocoder::Calculations

def endpoint(start, heading, distance, options = {})


which returns a [lat,lon] array
* a geocoded object (one which implements a +to_coordinates+ method
* a geocodable address (string)
* an array of coordinates ([lat,lon])

Geocoder methods that accept points as arguments. It can be:
The starting point is given in the same way that points are given to all
an endpoint.
Given a start point, distance, and heading (in degrees), provides
# 
def endpoint(start, heading, distance, options = {})
  options[:units] ||= Geocoder.config.units
  radius = earth_radius(options[:units])
  start = extract_coordinates(start)
  # convert degrees to radians
  start = to_radians(start)
  lat = start[0]
  lon = start[1]
  heading = to_radians(heading)
  distance = distance.to_f
  end_lat = Math.asin(Math.sin(lat)*Math.cos(distance/radius) +
                Math.cos(lat)*Math.sin(distance/radius)*Math.cos(heading))
  end_lon = lon+Math.atan2(Math.sin(heading)*Math.sin(distance/radius)*Math.cos(lat),
                Math.cos(distance/radius)-Math.sin(lat)*Math.sin(end_lat))
  to_degrees [end_lat, end_lon]
end