Question

I am trying to use google maps API V3 to draw a line from a default starting point and into a given direction given the distance. So for instance lets say my default starting point was San Francisco and the user inputs a distance, I want to be able to draw a straight line going eastward across the US based on that input distance. I came across this thing called bearing but im not sure how to use it correctly. Here is the code that I am working with:

function initializeMap(){

var mapOptions = {
center: new google.maps.LatLng(36.033036, -93.8655744),
zoom: 4,
mapTypeId: google.maps.MapTypeId.ROADMAP
};   

var map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions);

var R = 6378137;
var dis = parseInt(document.form['input']['val'].value);
var bearing = 80; 
var lat2 = Math.asin(   Math.sin(37.470625)*Math.cos(dis/R)+Math.cos(37.470625)*Math.sin(dis/R)*Math.cos(bearing) );
var lon2 = -122.266823 + Math.atan2(Math.sin(bearing)*Math.sin(dis/R)*Math.cos(37.470625),Math.cos(dis/R)-Math.sin(37.470625)*Math.sin(-122.266823));


var impactP = new google.maps.Polyline({
  path: new google.maps.LatLng(lat2,lon2), 
              strokeColor: "#FF0000",
  strokeOpacity: 1.0,
          strokeWeight: 2
        });
impactP.setMap(map);
}

Can someone help me out please. I really want to get this to work.

Answer 1

I put in the Google Maps scaffolding http://jsfiddle.net/khwLd/ but my math is off 🙁 You can see the lines veer off to the south. Googling “find terminal coordinates given a bearing and a distance” gave me a python function which I converted and checked but is still not giving the expected result.

Calculating coordinates given a bearing and a distance

What you need to do is fix all the math at the beginning so that:

getDestination(origin_lat, origin_lng, bearing, distance) returns google.maps.LatLng(destination_lat, destination_lng)

Sorry I wasn’t able to produce a full working solution 🙁