Getting LatLong of point on circle based on given angle

Question

Given that you have this circle defined on your map, how would you get the LatLong of the point that intersects at a given angle?

var degrees = 90;
var center = {lat: 34.052235, lng: -118.243683};
var circle = new google.maps.Circle({
    center: center,
    radius: 500000
});

var pointOnCircle = ?

Uhm, you have already the coordinate and the radius of the circle? — KarelG, Oct 02 '17 at 12:59
@KarelG I don't think you understand what I'm asking. I want to be able to input any given angle to get a point on the circle. — Merilynn Bandy, Oct 02 '17 at 13:02
Use some trigonometry to find the distances. `rcos(θ)` and `rsin(θ)`. Then add to the current coordinates. — Andrew Li, Oct 02 '17 at 13:05
@AndrewLi Provide some code for your answer? I have no idea how to do this. — Merilynn Bandy, Oct 02 '17 at 13:17
duplicate of duplicate? https://stackoverflow.com/questions/839899/how-do-i-calculate-a-point-on-a-circle-s-circumference — Neoares, Oct 02 '17 at 13:21
@Neoares This isn't a duplicate. I'm asking specifically how to find a **latitude** and **longitude** on Google Maps. This requires not only code to solve but knowledge of how to convert from meters to LatLong. — Merilynn Bandy, Oct 02 '17 at 13:24
@whimzee you can not convert from meters to LatLong an easy way, since the Earth is not a perfect sphere... so if there is a solution, it should be given by google maps (which I don't know) — Neoares, Oct 02 '17 at 13:34

score 1 · Accepted Answer · answered Oct 02 '17 at 13:52

You can use the geometry library computeOffset method:

  var pointOnCircle = google.maps.geometry.spherical.computeOffset(circle.getCenter(), circle.getRadius(), degrees);

proof of concept fiddle

code snippet:

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 degrees = 90;
  var center = {
    lat: 34.052235,
    lng: -118.243683
  };
  var circle = new google.maps.Circle({
    center: center,
    radius: 500000,
    map: map
  });
  map.fitBounds(circle.getBounds());
  var pointOnCircle = google.maps.geometry.spherical.computeOffset(circle.getCenter(), circle.getRadius(), degrees);
  var marker = new google.maps.Marker({
    map: map,
    position: pointOnCircle
  });
  var polyline = new google.maps.Polyline({
    map: map,
    path: [circle.getCenter(), pointOnCircle]
  })
}
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>

Getting LatLong of point on circle based on given angle

1 Answers1