geo-distance-js/index.js

A Node.js module which takes 2 Lat+Lng (Geolocation) points and returns the distance between the two points in Meters

/**
 * Simple node js module to get distance between two coordinates.
 * Code transformed from Chris Veness example code - please refer to his website for licensing questions.
 *
 * Latitude/longitude spherical geodesy formulae & scripts (c) Chris Veness 2002-2011
 * www.movable-type.co.uk/scripts/latlong.html
 */

/** Converts numeric degrees to radians */
if (typeof(Number.prototype.toRad) === 'undefined') {
    Number.prototype.toRad = function () {
        return this * Math.PI / 180;
    };
}

exports.distances = {
    'yards': 6967410,
    'km': 6371,
    'miles': 3959,
    'metres': 6371000,
    'feet': 20902231
};

/**
 * Sort the to object in ascending or descending order if called
 * @param  {object} toObj      [Going to Lng, Lat and distance]
 * @param  {number} toObj.lat  [Latitude]
 * @param  {number} toObj.lng  [Longitutde]
 * @param  {number} toObj.distance [Distance]
 * @param  {string} orderBy [Ascending or Descending]
 * @return {object}         [Object to, in order by distance]
 */
exports.distanceSort = function (toObj, orderBy) {
    toObj.sort(function (a, b) {
        var a1 = a.distance, b1 = b.distance;
        if (a1 == b1) { return 0; }
        return a1> b1 ? 1 : -1;
    });

    if (orderBy != 'asc') {
        toObj.reverse();
    }

    return toObj;
};

/**
 * Function which calculates a single distance between two points
 * @function retrieveDistance
 * @memberOf geoDistance
 * @param  {object} data [Created by the run function]
 * @param  {number} data.earthRadius [Contains the radius]
 * @param  {number} data.decimals [Contains the amount of decimals]
 * @param  {number} data.dLat [From minus to Lat radian]
 * @param  {number} data.dLng [From minus to Lng radian]
 * @param  {number} data.toLat [To Latitude]
 * @param  {number} data.toLng [To Longitude]
 * @param  {number} data.fromLat [From Latitude radian]
 * @return {number}      [Returns the caculated distance]
 */
exports.retrieveDistance = function (data) {
    var earthRadius = data.earthRadius,
        decimals = data.decimals,
        dLat = data.dLat,
        dLng = data.dLng,
        toLat = data.toLat,
        toLng = data.toLng,
        fromLat = data.fromLat,

        a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
            Math.sin(dLng / 2) * Math.sin(dLng / 2) * Math.cos(toLat) *
            Math.cos(fromLat),
        b = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)),
        c = earthRadius * b,
        d = (Math.round(c * Math.pow (10, decimals)) /
            Math.pow(10, decimals)) * 1000;

    return d;
};

/**
 * Function to retrieve the difference in a human readable length such
 * as km between two difference longitude and latitude points
 * @function init
 * @memberOf geoDistance
 *
 * @param  {object} from    [Contains the main starting lng/lat point]
 * @param  {number} from.lat [Latitude]
 * @param  {number} from.lng [Longitutde]
 * @param  {array<object>}  to [Can contain multiple end lng/lat points]
 * @param  {number} to.lat [Latitude]
 * @param  {number} to.lng [Longitude]
 *
 * @return {Object}          [Returns the to object with the distance]
 */
exports.getDistance = function (from, to, orderBy, length, decimals) {
    decimals = decimals || 2;
    length = length || 'km';

    var fromObj = from,
        toObj = to.slice(0),
        earthRadius = this.distances[length],
        fromLng = parseFloat(fromObj.lng),
        fromLat = parseFloat(fromObj.lat);

    fromLat = fromLat.toRad();

    for (var i = to.length - 1; i >= 0; i--) {
        var lngLat = toObj[i],
            toLat = parseFloat(lngLat.lat),
            toLng = parseFloat(lngLat.lng),
            dLat = (fromLat - toLat).toRad(),
            dLng = (fromLng - toLng).toRad(),
            data = {
                earthRadius: earthRadius,
                decimals: decimals,
                dLat: dLat,
                dLng: dLng,
                toLng: toLng,
                fromLat: fromLat
            };

        data.toLat = toLat.toRad();

        toObj[i].distance = this.retrieveDistance(data);
    }

    if (orderBy) {
        toObj = this.distanceSort(toObj, orderBy);
    }

    return toObj;
};