javascript - 在 Javascript 中使用 Haversine 公式

Question

我正在尝试使用 Haversine 距离公式(如在此处找到:http://www.movable-type.co.uk/scripts/latlong.html)但我无法让它工作，请参阅以下代码

    function test() { 
    var lat2 = 42.741; 
    var lon2 = -71.3161; 
    var lat1 = 42.806911; 
    var lon1 = -71.290611; 

    var R = 6371; // km 
    //has a problem with the .toRad() method below.
    var dLat = (lat2-lat1).toRad();  
    var dLon = (lon2-lon1).toRad();  
    var a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
                    Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) * 
                    Math.sin(dLon/2) * Math.sin(dLon/2);  
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
    var d = R * c; 

    alert(d); 
}

错误是:

Uncaught TypeError: Object -0.06591099999999983 has no method 'toRad' 

我理解是因为它需要执行以下操作:

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

但是当我把它放在函数下面时，它仍然会返回相同的错误消息。如何使它使用辅助方法？或者是否有另一种方法来编写代码以使其工作？谢谢!

Answer 1

此代码有效:

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

var lat2 = 42.741; 
var lon2 = -71.3161; 
var lat1 = 42.806911; 
var lon1 = -71.290611; 

var R = 6371; // km 
//has a problem with the .toRad() method below.
var x1 = lat2-lat1;
var dLat = x1.toRad();  
var x2 = lon2-lon1;
var dLon = x2.toRad();  
var a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
                Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) * 
                Math.sin(dLon/2) * Math.sin(dLon/2);  
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
var d = R * c; 

alert(d);

注意我是如何定义 x1 和 x2 的。
与它一起玩: https://tinker.io/3f794