diff --git a/includes/geo/sceneindex.php b/includes/geo/sceneindex.php
index e071354..5217ec5 100755
--- a/includes/geo/sceneindex.php
+++ b/includes/geo/sceneindex.php
@@ -1,214 +1,218 @@
 <?php
 
 /**
  * Geo scene index class.
  *
  * Zed. The immensity of stars. The HyperShip. The people.
  *
  * (c) 2010, Dereckson, some rights reserved.
  * Released under BSD license.
  *
  * @package     Zed
  * @subpackage  Geo
  * @author      Sébastien Santoro aka Dereckson <dereckson@espace-win.org>
  * @copyright   2010 Sébastien Santoro aka Dereckson
  * @license     http://www.opensource.org/licenses/bsd-license.php BSD
  * @version     0.1
  * @link        http://scherzo.dereckson.be/doc/zed
  * @link        http://zed.dereckson.be/
  * @filesource
  *
  * This class implements a singleton pattern.
  */
 
 require_once('includes/cache/cache.php');
 
 /**
  * Geo scene class
  *
  * This class provides an index of available scene template files.
  */
 class GeoSceneIndex {
     /**
      * Global location templates array
      *
      * Keys are global location codes.
      * Values the relevant template file.
      *
      * @var Array
      */
     public $global_templates;
 
     /**
      * Rocal location templates 2D array
      *
      * Keys are global and local ocation codes.
      * Values the relevant template file.
      *
      * e.g. $local_templates['B00017001']['(10, 50, 8)'] => 'B00017_port.tpl'
      *
      * @var Array
      */
     public $local_templates;
 
     /**
      * Time of the last updated file in the scenes directory
      *
      * @var int
      */
     public $updated;
 
     /**
      * The directory where templates are stored
      *
      * @var string
      */
     public $directory;
 
     /**
      * The current index instance array
      *
      * Keys are scene directories (string)
      * Items are GeoSceneIndex instances
      *
      * @var Array
      */
     static $instance = array();
 
     /**
      * Gets the index instance, initializing it if needed
      *
      * @return index the index instance
      */
     static function load ($directory) {
         //Creates the index object if needed
         if (!array_key_exists($directory, self::$instance)) {
             self::$instance[$directory] = new GeoSceneIndex($directory);
         }
 
         return self::$instance[$directory];
     }
 
     /**
      * Initializes a new GeoSceneIndex istance
      *
      * @param string $directory the scene templates directory
      */
     public function __construct ($directory) {
         $this->directory = $directory;
         if (!$this->get_cached_information() || !$this->is_up_to_date()) {
                 $this->refresh_information();
                 $this->set_cached_information();
         }
     }
 
     /**
      * Caches index data
      */
     public function set_cached_information () {
         $cache = Cache::load();
         $cache->set('zed_sceneindex', serialize($this));
     }
 
     /**
      * Gets index from cache
      */
     public function get_cached_information () {
         $cache = Cache::load();
         $cached_index =$cache->get('zed_sceneindex');
         if ($index = unserialize($cache->get('zed_sceneindex'))) {
             $index = unserialize($cache->get('zed_sceneindex'));
             $this->global_templates = $index->global_templates;
             $this->local_templates = $index->local_templates;
             $this->updated = $index->updated;
             $this->directory = $index->directory;
             return true;
         }
         return false;
     }
 
     /**
      * Reads scene templates and indexes information
      */
     public function refresh_information () {
         $this->global_templates = array();
         $this->local_templates = array();
         $this->updated = filemtime($this->directory);
         if ($handle = opendir($this->directory)) {
             while (false !== ($file = readdir($handle))) {
                  if (GeoScene::get_file_extension($file) == 'tpl') {
                     $template = file_get_contents($this->directory . '/' . $file, false, NULL, 0, 1024);
                     $location = self::get_template_location($template);
                     if ($location[1] !== NULL) {
                         $this->local_templates[$location[0]][$location[1]] = $file;
                     } elseif ($location[0] != NULL) {
                         $this->global_templates[$location[0]] = $file;
                     }
                  }
             }
             closedir($handle);
         }
     }
 
     /**
      * Determines if the information is still up to date
      *
      * @return bool true if the information is up to date ; otherwise, false.
      */
     public function is_up_to_date () {
         return ($this->updated == filemtime($this->directory));
     }
 
     /**
      * Gets template location
      *
      * @return Array an string array of the location (two items; global, local)
      *  At key 0, a string with global location, or NULL if not specified
      *  At key 1, a string with local location, or NULL if not specified
      */
     private static function get_template_location ($template) {
         $location = array(NULL, NULL);
 
         //Gets global location
-        $pos1 = strpos($template, "Global location: ") + 17;
+        $pos1 = strpos($template, "Global location: ");
+        if ($pos1 === false) {
+            throw new Exception("No location in template. Any template file must contain a comment line with the string 'Global location: ' followed by the global location matching the template. It should also contains a line 'Local location: ' when applicable.");
+        }
+        $pos1 += 17;
         $pos2 = strpos($template, "\n", $pos1);
         $location[0] = trim(substr($template, $pos1, $pos2 - $pos1));
 
         //Gets local location
         $pos1 = strpos($template, "Local location: ");
         if ($pos1 !== false) {
             $pos1 += 16;
             $pos2 = strpos($template, "\n", $pos1);
             $location[1] = trim(substr($template, $pos1, $pos2 - $pos1));
         }
 
         return $location;
     }
 
     /**
      * Gets local template file from index
      *
      * @param string $location_global the global location
      * @param string $location_global the local location
      * @return string the relevant template scene file, or NULL if not existant
      */
     public function get_local_template ($location_global, $location_local) {
         if (isset($this->local_templates[$location_global][$location_local])) {
             return $this->local_templates[$location_global][$location_local];
         }
         return NULL;
     }
 
     /**
      * Gets global template file from index
      *
      * @param string $location_global the global location
      * @return string the relevant template scene file, or NULL if not existant
      */
     public function get_global_template ($location_global) {
         if (isset($this->global_templates[$location_global])) {
             return $this->global_templates[$location_global];
         }
         return NULL;
     }
 }