Hi.

I am new to the googlemaps API. I have written a small app for my mobile phone that periodically updates its location to an SQL databse.

I would like to display this information on a googlemap in my browser. Ideally i'd like to then poll the database periodically and if any new co-ords have arrived, add them to the line.

Best way of describing it is this;

http://tiny.cc/HEIa0

In a quest to get to there, i've started on the documents on google and been modifying them to try and acheive what I want. It doesn't work - and i don't know enough to know why. I would love some advice as to why, and any pointers towards my ultimate goal would be very much welcomed. Google Maps AJAX + MySQL/PHP Example

   <script type="text/javascript">
  //<![CDATA[

function load() {
  if (GBrowserIsCompatible()) {
    var map = new GMap2(document.getElementById("map"));
    map.addControl(new GSmallMapControl());
    map.addControl(new GMapTypeControl());
    map.setCenter(new GLatLng(47.614495, -122.341861), 13);

    GDownloadUrl("phpsqlajax_genxml.php", function(data) {
      var xml = GXml.parse(data);
      var line = [];
      var markers = xml.documentElement.getElementsByTagName("points");
        for (var i = 0; i < points.length; i++) {
            var point = points.item(i);
            var lat  = point.getAttribute("lat");
            var lng  = point.getAttribute("lng");

            var latlng = new GLatLng(lat, lng);

       line.push(latlng);
       if (point.firstChild) {
         var station = point.firstChild.nodeValue;
         var marker = createMarker(latlng, station);
         map.addOverlay(marker);
       }
     }

     var polyline = new GPolyline(line, "#ff0000", 3, 1);
     map.addOverlay(polyline);
});
}
//]]>

My php file is generating the following XML;

<?xml version="1.0" encoding="UTF-8" ?>
<points>
<point lng="-122.340141" lat="47.608940"/>
<point lng="-122.344391" lat="47.613590"/>
<point lng="-122.356445" lat="47.624561"/>
<point lng="-122.337654" lat="47.606365"/>
<point lng="-122.345673" lat="47.612823"/>
<point lng="-122.340363" lat="47.605961"/>
<point lng="-122.345467" lat="47.613976"/>
<point lng="-122.326584" lat="47.617214"/>
<point lng="-122.342834" lat="47.610126"/>
</points>

I have successfully worked through this; http://code.google.com/apis/maps/articles/phpsqlajax.html before attempting to customise the code.

Any pointers? Where am I go wrong?