Utility for lat lng calculations

geolatlnglib

/**
 * @name geolatlnglib
 * @description utilities for lat lng calculations
 * @author Carlos Justiniano
 */

//http://stackoverflow.com/questions/27928/how-do-i-calculate-distance-between-two-latitude-longitude-points
function getDistanceFromLatLonInKm(lat1, lon1, lat2, lon2) {
  'use strict';
  var R = 6371; // Radius of the earth in km
  var dLat = deg2rad(lat2 - lat1);  // deg2rad below
  var dLon = deg2rad(lon2 - lon1);
  var a =
      Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) *
          Math.sin(dLon / 2) * Math.sin(dLon / 2)
    ;
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  var d = R * c; // Distance in km
  return d;
}

function deg2rad(deg) {
  'use strict';
  return deg * (Math.PI / 180);
}

exports.getDistance = function(lat1, lng1, lat2, lng2) {
  'use strict';
  return getDistanceFromLatLonInKm(lat1, lng1, lat2, lng2) / 0.621371;   // return distance in miles
};