javascript - 查找距离另一个坐标一定距离的坐标

Question

我正在使用Google map 几何库来计算两点之间的距离和航向:

...computeDistanceBetween(coord1, coord2) // = 10 m.
...computeHeading(coord1, coord2) // = 25

我想根据另一个已知坐标(也是 10 m)找到一个点。远离，朝同一方向(标题):

...computeDistanceBetween(coord3, unknown) // = 10 m.
...computeHeading(coord3, unknown) // = 25

在这种情况下如何计算未知数？

Answer 1

使用computeOffset。来自 the documentation :

computeOffset(from:LatLng, distance:number, heading:number, radius?:number)

Return Value: LatLng

Returns the LatLng resulting from moving a distance from an origin in the specified heading (expressed in degrees clockwise from north).

var distance = google.maps.geometry.spherical.computeDistanceBetween(coord1, coord2);
var heading = google.maps.geometry.spherical.computeHeading(coord1, coord2);
var newPt = google.maps.geometry.spherical.computeOffset(coord1, distance/2, heading);

代码片段:

function initialize() {
  var map = new google.maps.Map(
    document.getElementById("map_canvas"), {
      center: new google.maps.LatLng(37.4419, -122.1419),
      zoom: 13,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    });
  var coord1 = new google.maps.LatLng(37.399228, -122.208676); // SouthWest corner
  var coord2 = new google.maps.LatLng(37.484548, -122.075124); // NorthEast corner
  var distance = google.maps.geometry.spherical.computeDistanceBetween(coord1, coord2);
  var heading = google.maps.geometry.spherical.computeHeading(coord1, coord2);
  var newPt = google.maps.geometry.spherical.computeOffset(coord1, distance / 2, heading);
  console.log(newPt.toUrlValue(6) + ", distance=" + distance.toFixed(2) + ", heading=" + heading);
  var marker = new google.maps.Marker({
    position: newPt,
    map: map
  });
}
google.maps.event.addDomListener(window, "load", initialize);

html,
body,
#map_canvas {
  height: 100%;
  width: 100%;
  margin: 0px;
  padding: 0px
}

<script src="https://maps.googleapis.com/maps/api/js?libraries=geometry"></script>
<div id="map_canvas"></div>