added doc link for r515's change

@@ -65,6 +65,7 @@
 }
 }
 -(float) maxZoom
 -(float) maxZoom
 {
 {
+	//http://wiki.openstreetmap.org/index.php/FAQ#What_is_the_map_scale_for_a_particular_zoom_level_of_the_map.3F 
 	return 18.0f;
 	return 18.0f;
 }
 }