하버사인 공식

        function toRadians(degree)

        {

            return degree * Math.PI / 180

        }

        function distance(latitude1, longitude1, latitude2, longitude2)

        {

            // R은 지구의 반지름, 단위는 km

            var R = 6371;

            var deltaLatitude = (latitude2 - latitude1).toRadians();

            var deltaLongitude = (longitude2 - longitude1).toRadians();

            latitude1 = latitude1.toRadians(),latitude2 = latitude2.toRadians();

            var a = Math.sin(deltaLatitude / 2) *

                    Math.sin(deltaLatitude / 2) +

                    Math.cos(latitude1) *

                    Math.cos(latitude2) *

                    Math.sin(deltaLongitude / 2) *

                    Math.sin(deltaLongitude / 2);

            var c = 2 * Math.atan2(Math.sqrt(a),

                    Math.sqrt(1 - a));

            var d = R * c;

            return d;

        }