text: function coordinateDistance(lat, lon, lat2, lon2) {
      var R = 6371; // Radius of the earth in km
      var dLat = (lat2 - lat) * Math.PI / 180; // deg2rad below
      var dLon = (lon2 - lon) * Math.PI / 180;
      var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
          Math.cos(lat * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
          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;
  }
  exports.coordinateDistance = coordinateDistance;
  