module Geocoder::Calculations

def bearing_between(point1, point2, options = {}, *args)


Based on: http://www.movable-type.co.uk/scripts/latlong.html

the same latitude)
is less confusing (returns due east or west when given two points with
(one along a great circle) but the linear method is the default as it
the spherical method is "correct" in that it returns the shortest path
* :method - :linear (default) or :spherical;

ways of specifying the points. Also accepts an options hash:
See Geocoder::Calculations.distance_between for

Returns a number of degrees from due north (clockwise).
Bearing between two points on Earth.
# 
def bearing_between(point1, point2, options = {}, *args)
  if args.size > 0
    warn "DEPRECATION WARNING: Instead of passing lat1/lon1/lat2/lon2 as separate arguments to the bearing_between method, please pass two two-element arrays: [#{point1},#{point2}], [#{options}, #{args.first}]. The old argument format will not be supported in Geocoder v.1.0."
    point1 = [point1, point2]
    point2 = [options, args.shift]
    options = args.shift || {}
  end
  options[:method] = :linear unless options[:method] == :spherical
  # convert to coordinate arrays
  point1 = extract_coordinates(point1)
  point2 = extract_coordinates(point2)
  # convert degrees to radians
  point1 = to_radians(point1)
  point2 = to_radians(point2)
  # compute deltas
  dlat = point2[0] - point1[0]
  dlon = point2[1] - point1[1]
  case options[:method]
  when :linear
    y = dlon
    x = dlat
  when :spherical
    y = Math.sin(dlon) * Math.cos(point2[0])
    x = Math.cos(point1[0]) * Math.sin(point2[0]) -
        Math.sin(point1[0]) * Math.cos(point2[0]) * Math.cos(dlon)
  end
  bearing = Math.atan2(x,y)
  # Answer is in radians counterclockwise from due east.
  # Convert to degrees clockwise from due north:
  (90 - to_degrees(bearing) + 360) % 360
end