Calculate the distance between two GPS Co-Ordinates with Ruby

latlondistance.rb

def distance_between(lat1,lon1,lat2,lon2, miles=false)
  r = 6371; # Kilometers

  dLat = to_radian(lat2-lat1);
  dLon = to_radian(lon2-lon1);
  lat1 = to_radian(lat1);
  lat2 = to_radian(lat2);
  
  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));
  d = r * c;
  if(miles)
    d = d * 0.62137
  end
  d
end

def to_radian(input)
  input * Math::PI / 180
end