arneheggestad/getcoordinates

var distance = {
    haversine: function (pointA, pointB) {
        var r = 6371 * 1000; // earth's mean radius in m
        // phi = latitude, lambda = longitude
        var lat1 = pointA.lat,
                lat2 = pointB.lat,
                long1 = pointA.lon,
                long2 = pointB.lon;
        var phi1 = lat1 * Math.PI / 180, // convert degrees to radians (2pi radians = 360 degrees)
                phi2 = lat2 * Math.PI / 180,
                deltaPhi = (lat2 - lat1) * Math.PI / 180,
                deltaLambda = (long2 - long1) * Math.PI / 180;

        var a = Math.sin(deltaPhi / 2) * Math.sin(deltaPhi / 2) +
                        Math.cos(phi1) * Math.cos(phi2) *
                        Math.sin(deltaLambda / 2) * Math.sin(deltaLambda / 2),
                c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)),
                d = r * c;
        return Math.round(d * 10) / 10; // return 1 decimal place
    }
}

module.exports = distance;