<script src="http://maps.googleapis.com/maps/api/js"></script>
<script>

var logitude = <?php echo get_post_meta($post->ID,'longitude', true); ?>
var latitude = <?php echo get_post_meta($post->ID, 'latitude', true);?>
function initialize(latitude,logitude) {

  var mapProp = {
    center:new google.maps.LatLng(latitude,logitude),
    zoom:5,
    mapTypeId:google.maps.MapTypeId.ROADMAP
  };
  var map=new google.maps.Map(document.getElementById("googleMap"),mapProp);
}
google.maps.event.addDomListener(window, 'load', initialize);
</script>