Haversine formula (http://en.wikipedia.org/wiki/Haversine_formula) in Ruby

distance.rb

  class Numeric
    def to_rad
      self * Math::PI / 180
    end
  end
 
  # http://www.movable-type.co.uk/scripts/latlong.html
  # loc1 and loc2 are arrays of [latitude, longitude]
  def distance loc1, loc2
     lat1, lon1 = loc1
     lat2, lon2 = loc2
     dLat = (lat2-lat1).to_rad;
     dLon = (lon2-lon1).to_rad;
     a = Math.sin(dLat/2) * Math.sin(dLat/2) +
         Math.cos(lat1.to_rad) * Math.cos(lat2.to_rad) *
         Math.sin(dLon/2) * Math.sin(dLon/2);
     c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
     d = 6371 * c; # Multiply by 6371 to get Kilometers
  end

This is an implementation of the haversine formula to calculate distances between two points on the globe.

Thanks Josh for the example!

Thanks, this helped me with an infovis project.

Ended up using the Haversine gem -- same results, but easier to use on my project.

Borrowed this for an example in our server monitoring tools.

Thanks!