module Geocoder::Calculations

def distance_between(point1, point2, options = {})


Use Geocoder.configure(:units => ...) to configure default units.
* :units - :mi or :km

The options hash supports:

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. They can be:
The points are given in the same way that points are given to all
Takes two points and an options hash.
Distance between two points on Earth (Haversine formula).
# 
def distance_between(point1, point2, options = {})
  # set default options
  options[:units] ||= Geocoder.config.units
  # 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]
  a = (Math.sin(dlat / 2))**2 + Math.cos(point1[0]) *
      (Math.sin(dlon / 2))**2 * Math.cos(point2[0])
  c = 2 * Math.atan2( Math.sqrt(a), Math.sqrt(1-a))
  c * earth_radius(options[:units])
end