domotz-remote-pawn/src/network_tools/earthDistance.js

Domotz Agent

/** This file is part of Domotz Agent.
  * Copyright (C) 2016  Domotz Ltd
  *
  * Domotz Agent is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
  *
  * Domotz Agent is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Domotz Agent.  If not, see <http://www.gnu.org/licenses/>.
  **/
/**
 *
 * Created by Iacopo Papalini <ipapalini@domotz.com> on 17/09/15.
 */

const HALF_EARTH_CIRCUMFERENCE = 20000; // Approximate, in km
const EARTH_RADIUS = 6371; // Approximate, in km

module.exports.distanceCalculator = function (configuration) {

    var myLatitude = null;
    var myLongitude = null;

    if (configuration && configuration.location) {
        myLatitude = configuration.location.latitude;
        myLongitude = configuration.location.longitude;
    }

    return {
        distanceTo: function (latitudeA, longitudeA, latitudeB, longitudeB) {

            if (latitudeA !== latitudeA || longitudeA !== longitudeA) {
                // one is NaN
                return HALF_EARTH_CIRCUMFERENCE;
            }

            if (myLatitude === null && myLongitude=== null && latitudeB != undefined && longitudeB != undefined) {
                myLatitude = latitudeB;
                myLongitude = longitudeB;
            }

            function deg2rad(d) {
                return d / 180 * Math.PI;
            }

            var deltaLatitude = deg2rad(latitudeA - myLatitude);
            var deltaLongitude = deg2rad(longitudeA - myLongitude);
            var a = (Math.sin(deltaLatitude / 2) *
                     Math.sin(deltaLatitude / 2) +
                     Math.cos(deg2rad(myLatitude)) *
                     Math.cos(deg2rad(latitudeA)) *
                     Math.sin(deltaLongitude / 2) *
                     Math.sin(deltaLongitude / 2));
            var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
            return Math.round(EARTH_RADIUS * c);
        }
    };
};