html5 geolocation

使用HTML5 Geolocation构建应用

一个重要的计算距离的公式，Haversine公式：

 详细定义参见：http://en.wikipedia.org/wiki/Haversine_formula

 

Number.prototype.toRadians = function() {
    return this * Matn.PI / 180;
}

function distance(latitude1, longitude1, latitude2, longitude2) {
    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;
}