如何在 JavaScript 中找到我到已知位置的距离
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How to find my distance to a known location in JavaScript
提问by Dalee
Using JavaScript in the browser, how can I determine the distance from my current location to another location for which I have the latitude and longitude?
在浏览器中使用 JavaScript，如何确定从我的当前位置到我有纬度和经度的另一个位置的距离？
回答by Frank van Puffelen
If your code runs in a browser, you can use the HTML5 geolocation API:
如果您的代码在浏览器中运行，您可以使用 HTML5 地理定位 API：
window.navigator.geolocation.getCurrentPosition(function(pos) {
console.log(pos);
var lat = pos.coords.latitude;
var lon = pos.coords.longitude;
})
Once you know the current position and the position of your "target", you can calculate the distance between them in the way documented in this question: Calculate distance between two latitude-longitude points? (Haversine formula).
一旦您知道当前位置和“目标”的位置，您就可以按照这个问题中记录的方式计算它们之间的距离：计算两个经纬度点之间的距离？（Haversine 公式）。
So the complete script becomes:
所以完整的脚本变成了：
function distance(lon1, lat1, lon2, lat2) {
var R = 6371; // Radius of the earth in km
var dLat = (lat2-lat1).toRad(); // Javascript functions in radians
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; // Distance in km
return d;
}
/** Converts numeric degrees to radians */
if (typeof(Number.prototype.toRad) === "undefined") {
Number.prototype.toRad = function() {
return this * Math.PI / 180;
}
}
window.navigator.geolocation.getCurrentPosition(function(pos) {
console.log(pos);
console.log(
distance(pos.coords.longitude, pos.coords.latitude, 42.37, 71.03)
);
});
Apparently I am 6643 meters from the center of Boston, MA right now (that's the hard-coded second location).
显然，我现在距离马萨诸塞州波士顿市中心 6643 米（这是硬编码的第二个位置）。
See these links for more information:
有关更多信息，请参阅这些链接：
