Google Maps How do I get the mid point of a polyline?

Posted on 2008-06-19
Last Modified: 2008-06-19
How would I caculate the mid point of the two points on the map point A and point B and place a marker for the mid point?

Here is the code I am working with.  A code snippit
it would be greatly appericated as I suck at math and would not know how to incorperate it into what I already have.

The points are being pulled from the database here is the link to the map and points  Map points xml

Thanks in advance

<script type="text/javascript">

    var geocoder;

    var map;

    var gmarkers = [];

    var lines = [];

    geocoder = new GClientGeocoder();



    var iconBlue = new GIcon(); 

    iconBlue.image = '';

    iconBlue.shadow = '';

    iconBlue.iconSize = new GSize(12, 20);

    iconBlue.shadowSize = new GSize(22, 20);

    iconBlue.iconAnchor = new GPoint(6, 20);

    iconBlue.infoWindowAnchor = new GPoint(5, 1);

    var iconRed = new GIcon(); 

    iconRed.image = '';

    iconRed.shadow = '';

    iconRed.iconSize = new GSize(12, 20);

    iconRed.shadowSize = new GSize(22, 20);

    iconRed.iconAnchor = new GPoint(6, 20);

    iconRed.infoWindowAnchor = new GPoint(5, 1);

    var customIcons = [];

    customIcons["restaurant"] = iconBlue;

    customIcons["bar"] = iconRed;

    function load() {

      if (GBrowserIsCompatible()) {

        map = new GMap2(document.getElementById("map"));

        map.addControl(new GSmallMapControl());

        map.addControl(new GMapTypeControl());

        map.setCenter(new GLatLng(47.614495, -122.341861), 4);

        GDownloadUrl("", function(data) {

          var xml = GXml.parse(data);

          var markers = xml.documentElement.getElementsByTagName("marker");

          for (var i = 0; i < markers.length; i++) {
























 function addToMap(point,marker_num,name,type,html,color) {

	// use a custom icon with letter A - Z

	var letter = String.fromCharCode("A".charCodeAt(0) + marker_num); 

// alert("addToMap("+marker_num+"="+letter+")");

        //  GLog.write(letter+j); 

	var myIcon = new GIcon(G_DEFAULT_ICON, "" + letter + ".png");


	myIcon.printImage = "" + letter + "ie.gif"

	myIcon.mozPrintImage = "" + letter + "ff.gif"


	var marker = new GMarker(point, {icon:myIcon});

        var infoWindowContent = "<b>"+name+"</b><br>type: "+type+"<br>"+html;

	GEvent.addListener(marker, "click", function() {




	// save the info we need to use later for the side_bar

	gmarkers[marker_num] = marker;

        if (gmarkers.length >= 2) {

//          alert("add polyline - gmarkers.length="+gmarkers.length);

          var linepoints = [gmarkers[gmarkers.length-2].getPoint(), 


//          alert(linepoints[0], linepoints[1]);

          var polyline = new GPolyline(linepoints,color, 2);






	return marker;


    function showAddress(markers, marker_num) {









      var color = markers[marker_num].getAttribute("color");

      var name = markers[marker_num].getAttribute("name");

      var address = markers[marker_num].getAttribute("address");

      var type = markers[marker_num].getAttribute("type");

      var html = markers[marker_num].getAttribute("html");

      if (!html) { html = "there is no html attribute for this marker";}


        function(point) { 

	  if (!point) { 

	    alert(address + " not found"); 


	  else { 

		map.setCenter(point, 4);

		var marker = addToMap(point, marker_num, name, type, html,color);

//                alert("gmarkers.length="+gmarkers.length);



          marker_num += 1;

          // note this is a recursive call, may cause problems if lots of markers

//          alert("markers.length="+markers.length+" marker_num="+marker_num);

          if (markers.length > marker_num) showAddress(markers, marker_num);







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Question by:Devain
  • 2

Accepted Solution

McCoin earned 500 total points
ID: 21822965
I've never used google maps before, but I did a little research and found this link

It has some replies and some code examples, I hope this helps

Author Comment

ID: 21823073
lol thanks forgot I posted this

Expert Comment

ID: 21823199
no problem,
no worries

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