distance from

gistfile1.rb

# http://www.movable-type.co.uk/scripts/latlong.html
def distance_from(place, unit = :km)
  radius = (unit == :km) ? 6371 : 3959
  dLat = (place.source[:lat] - source[:lat]) * Math::PI / 180
  dLon = (place.source[:lng] - source[:lng]) * Math::PI / 180
  lat1 = source[:lat] * Math::PI / 180
  lat2 = place.source[:lat] * Math::PI / 180

  a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1) * Math.cos(lat2) 
  c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a))
  radius * c
end