Ajax using Google Maps API call returning -1

I’m struggling with using ajax calls in wordpress. I know my ajax calls were working prior to migrating the code into WordPress so it’s really only the wp ajax that is in question. If I enter https://localhost/wp-admin/admin-ajax.php?wwta_site_fill into my browser address bar I’m getting back -1. I don’t understand why my function isn’t being found/called.

below is the php code from my main plugin file which is setting up the ajax stuff (I’ve tried to trim my code down as much as I could leaving only what’s relevant):

add_action('wp_ajax_ta_site_fill', 'ta_ajax_site_fill');
add_action('wp_ajax_nopriv_ta_site_fill', 'ta_ajax_site_fill');

function ta_ajax_site_fill(){
	// qurey DB and build xml data
	...snip...
	// Start XML file, create parent node
	$dom = new DOMDocument("1.0");
	$node = $dom->createElement("marker");
	$parnode = $dom->appendChild($node);
	...snip...
	echo $dom->saveXML();
	die();
}

function ta_map_load_scripts(){
	$ta_options = get_option('ta_map_options');
	wp_register_script('ta_gmap_ref', 'https://maps.googleapis.com/maps/api/js?key=' . $ta_options["api_key"] . '&sensor=false',array(),NULL);
	wp_register_script('ta_gmap_local_js',WP_PLUGIN_URL.'ta_site_map.js',array(jquery),NULL);
	wp_enqueue_script('ta_gmap_ref',array(),NULL);
	wp_enqueue_script('ta_gmap_local_js',plugins_url('ta_site_map.js',__FILE__),array(),NULL);
	wp_localize_script('ta_gmap_local_js','wp_ta_map_vars',array(
		'local_path'=>plugins_url(__file__),
		'ajaxurl'=> admin_url('admin-ajax.php')
	));
}

add_action('wp_enqueue_scripts','ta_map_load_scripts');

Here’s my js I’m using google maps javascript api.

//<![CDATA[
    function gmap_load() {
      var map = new google.maps.Map(document.getElementById("map"), {
        center: --snip--
      });
      var infoWindow = new google.maps.InfoWindow;
      downloadUrl( wp_ta_map_vars.ajaxurl + "?ta_site_fill", function(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName("marker");
        for (var i = 0; i < element1.length; i++) {
          var ---snip---;
          var baloonhtml = "<b> <a target=\"_blank\" href="+wp_wwta_map_vars.local_path+"/site_detail_template.php?siteID=" + siteID + ">" + name + "</a> </b> <br/>" + steloc;
          var marker = new google.maps.Marker({
            map: map,
            position: point,
            title: name
          });
          bindInfoWindow(marker, map, infoWindow, baloonhtml);
        }
      });
    }

    function bindInfoWindow(marker, map, infoWindow, html) {
      google.maps.event.addListener(marker, 'click', function() {
        infoWindow.setContent(html);
        infoWindow.open(map, marker);
      });
    }
    function downloadUrl(url, callback) {
      var request = window.ActiveXObject ?
          new ActiveXObject('Microsoft.XMLHTTP') :
          new XMLHttpRequest;
      request.onreadystatechange = function() {
        if (request.readyState == 4) {
          request.onreadystatechange = doNothing;
          callback(request, request.status);
        }
      };
      request.open('GET', url, true);
      request.send(null);
    }
    function doNothing() {}
    //]]>

Thank you taking the time to look at my issue,
Jason