如何在 JavaScript 中找到我到已知位置的距离

How to find my distance to a known location in JavaScript(如何在 JavaScript 中找到我到已知位置的距离)

问题描述

在浏览器中使用 JavaScript，我如何确定从我当前位置到另一个我知道经纬度的位置的距离?

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?

推荐答案

如果您的代码在浏览器中运行，您可以使用 HTML5 地理定位 API:

If your code runs in a browser, you can use the HTML5 geolocation API:

window.navigator.geolocation.getCurrentPosition(function(pos) { 
  console.log(pos); 
  var lat = pos.coords.latitude;
  var lon = pos.coords.longitude;
})

一旦您知道目标"的当前位置和位置，您就可以按照此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).

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).

所以完整的脚本变成了:

So the complete script becomes:

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)
  ); 
});

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).

Apparently I am 6643 meters from the center of Boston, MA right now (that's the hard-coded second location).

查看这些链接了解更多信息:

See these links for more information:

• http://html5demos.com/geo
• http://diveintohtml5.info/geolocation.html
• 计算两个经纬度点之间的距离?(Haversine 公式)
• toRad() Javascript 函数抛出错误

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