Ruby script for the find distance between two points using haversine formula

distance_away_report.rb

RAD_PER_DEG = 0.017453293
Rmiles = 3956

def haversine_distance(lat1, lon1, lat2, lon2)
  dlon = lon2 - lon1
  dlat = lat2 - lat1

  dlon_rad = dlon * RAD_PER_DEG
  dlat_rad = dlat * RAD_PER_DEG

  lat1_rad = lat1 * RAD_PER_DEG
  lon1_rad = lon1 * RAD_PER_DEG

  lat2_rad = lat2 * RAD_PER_DEG
  lon2_rad = lon2 * RAD_PER_DEG

  a = (Math.sin(dlat_rad / 2)) ** 2 + Math.cos(lat1_rad) * Math.cos(lat2_rad) * (Math.sin(dlon_rad / 2)) ** 2
  c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a))
  Rmiles * c
end