Distance between a searched address and nearest existing placemark on a google maps api v3

Question

I'm developing a web page with a Google Maps API v3. I currently have a functional map and search bar. I need to be able to display the distance from a searched address to the nearest placemark on one of the KML files on the map. How can I do this?

Here is the code for the page:

<script type="text/javascript">
    var geocoder;
    var map; 
    var marker;
    var layers = [];
  function initialize() {
    geocoder = new google.maps.Geocoder ();
    var latlng = new google.maps.LatLng (41, -73.4);
    var myOptions = {
      zoom: 7,
      center: latlng,
      mapTypeId: google.maps.MapTypeId.ROADMAP
        }
      map = new google.maps.Map(document.getElementById("map_canvas"),
        myOptions);
      marker = new google.maps.Marker({map:map});


        layers[0] = new google.maps.KmlLayer('http://dl.dropbox.com/u/80233620/South-and-North-County-Trailway.kml',
            {preserveViewport: true});
        layers[1] = new google.maps.KmlLayer('http://www.nyc.gov/html/dot/downloads/misc/cityracks.kml', 
            {preserveViewport: true});
        layers[2] = new google.maps.KmlLayer('http://dl.dropbox.com/u/80233620/NWS%20Radar%20Images.kmz', 
            {preserveViewport: true});
    for (var i = 0; i < layers.length; i++) {
                layers[i].setMap(map);
              }
        }

    function codeAddress () {
        var address = document.getElementById ("address").value;
        geocoder.geocode ( { 'address': address}, function(results, status)  {
        if (status == google.maps.GeocoderStatus.OK)  {
            map.setCenter(results [0].geometry.location);
            marker.setPosition(results [0].geometry.location);
            map.setZoom(14);
            } 
        else {
            alert("Geocode was not successful for the following reason: " + status);
                }
        }); 
                            }
    function toggleLayer(i) {
      if(layers[i].getMap() === null) {
        layers[i].setMap(map);
      }
      else {
        layers[i].setMap(null);}
    }

</script>

Answer 1

You cannot access the data in KML layers like that

https://developers.google.com/maps/documentation/javascript/layers#KMLLayers

Because KML may include a large number of features, you may not access feature data from the KmlLayer object directly. Instead, as features are displayed, they are rendered to look like clickable Maps API overlays.

Instead you can process the XML and add markers manually, then use the geometry library and computeDistanceBetween() to get the distance. I usually multiply the distance by some number to account for turns (The distance formula gets a straight line distance). I believe around 1.2 was the most accurate.