geo-distances/lib/index.js

A geographical distance calculator. Calculates distance between two points using haversine formula.

'use strict';

let radiusUnits = {
    'feet': 20908800,
    'yards': 6969600,
    'miles': 3960,
    'mi': 3960,
    'kilometers': 6371,
    'km': 6371,
    'meters': 6371000
};

class Utils {

    /**
    * Return distance between two co-ordinates point
    * 
    * @param {Object} lat1 Point one Latitude
    * @param {Object} lon1 Point one Longitude
    * @param {Object} lat2 Point two Latitude
    * @param {Object} lon2 Point two Longitude
    * @returns {number}
    */

    distance(lat1, lon1, lat2, lon2, unit) {
        let RaE = getEarthRadius(unit);
        let dLat = degreeToRadian(lat2 - lat1);
        let dLon = degreeToRadian(lon2 - lon1);
        return distance_formula(RaE, dLat, dLon, lat1, lat2);
    }

}

/**
 * 
 * @param {number} degree degree
 * @returns {number} 
 */

let degreeToRadian = (degree) => {
    return degree * (Math.PI / 180);
}


    /**
    * Haversine formula
    * 
    * @param {number} RaE Radius of Earth
    * @param {number} dLat difference between Latitude
    * @param {number} dLone difference between longitude
    * @param {number} lat1 point one lattitude
    * @param {number} lat2 point two lattitude
    * @returns {number}
    */

let distance_formula = (RaE, dLat, dLon, lat1, lat2) => {
    let calc1 = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(degreeToRadian(lat1)) * Math.cos(degreeToRadian(lat2))
        * Math.sin(dLon / 2) * Math.sin(dLon / 2)

    let calc2 = 2 * Math.atan2(Math.sqrt(calc1), Math.sqrt(1 - calc1))
    return RaE * calc2
}

    /**
    * Return Earth Radius in different units
    * 
    * @param {String} unit unit of measurement
    * @returns {number}
    */

let getEarthRadius = ((unit) => {
    if (unit == null) {
        unit = "km";
    }
    unit = unit.toLowerCase();
    if (!radiusUnits[unit]) {
        unit = "km";
    }
    return radiusUnits[unit];
})


module.exports = new Utils();