diff --git a/apps/openmw/mwbase/world.hpp b/apps/openmw/mwbase/world.hpp
index 9ee9db48c..fd8a10af8 100644
--- a/apps/openmw/mwbase/world.hpp
+++ b/apps/openmw/mwbase/world.hpp
@@ -414,7 +414,7 @@ namespace MWBase
             virtual void getItemsOwnedBy (const MWWorld::ConstPtr& npc, std::vector<MWWorld::Ptr>& out) = 0;
             ///< get all items in active cells owned by this Npc
 
-            virtual bool getLOS(const MWWorld::Ptr& actor,const MWWorld::Ptr& targetActor) = 0;
+            virtual bool getLOS(const MWWorld::ConstPtr& actor,const MWWorld::ConstPtr& targetActor) = 0;
             ///< get Line of Sight (morrowind stupid implementation)
 
             virtual float getDistToNearestRayHit(const osg::Vec3f& from, const osg::Vec3f& dir, float maxDist) = 0;
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index 495880469..39e212c0b 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -857,7 +857,7 @@ namespace MWPhysics
         const btCollisionObject* mMe;
     };
 
-    PhysicsSystem::RayResult PhysicsSystem::castRay(const osg::Vec3f &from, const osg::Vec3f &to, MWWorld::Ptr ignore, int mask, int group)
+    PhysicsSystem::RayResult PhysicsSystem::castRay(const osg::Vec3f &from, const osg::Vec3f &to, MWWorld::Ptr ignore, int mask, int group) const
     {
         btVector3 btFrom = toBullet(from);
         btVector3 btTo = toBullet(to);
@@ -865,7 +865,7 @@ namespace MWPhysics
         const btCollisionObject* me = NULL;
         if (!ignore.isEmpty())
         {
-            Actor* actor = getActor(ignore);
+            const Actor* actor = getActor(ignore);
             if (actor)
                 me = actor->getCollisionObject();
         }
@@ -912,10 +912,10 @@ namespace MWPhysics
         return result;
     }
 
-    bool PhysicsSystem::getLineOfSight(const MWWorld::Ptr &actor1, const MWWorld::Ptr &actor2)
+    bool PhysicsSystem::getLineOfSight(const MWWorld::ConstPtr &actor1, const MWWorld::ConstPtr &actor2) const
     {
-        Actor* physactor1 = getActor(actor1);
-        Actor* physactor2 = getActor(actor2);
+        const Actor* physactor1 = getActor(actor1);
+        const Actor* physactor2 = getActor(actor2);
 
         if (!physactor1 || !physactor2)
             return false;
diff --git a/apps/openmw/mwphysics/physicssystem.hpp b/apps/openmw/mwphysics/physicssystem.hpp
index ce611a4d0..09a76e208 100644
--- a/apps/openmw/mwphysics/physicssystem.hpp
+++ b/apps/openmw/mwphysics/physicssystem.hpp
@@ -107,12 +107,12 @@ namespace MWPhysics
 
             /// @param me Optional, a Ptr to ignore in the list of results
             RayResult castRay(const osg::Vec3f &from, const osg::Vec3f &to, MWWorld::Ptr ignore = MWWorld::Ptr(), int mask =
-                    CollisionType_World|CollisionType_HeightMap|CollisionType_Actor, int group=0xff);
+                    CollisionType_World|CollisionType_HeightMap|CollisionType_Actor, int group=0xff) const;
 
             RayResult castSphere(const osg::Vec3f& from, const osg::Vec3f& to, float radius);
 
             /// Return true if actor1 can see actor2.
-            bool getLineOfSight(const MWWorld::Ptr& actor1, const MWWorld::Ptr& actor2);
+            bool getLineOfSight(const MWWorld::ConstPtr& actor1, const MWWorld::ConstPtr& actor2) const;
 
             bool isOnGround (const MWWorld::Ptr& actor);
 
diff --git a/apps/openmw/mwworld/refdata.cpp b/apps/openmw/mwworld/refdata.cpp
index 6c89f6d6f..1da6b53fa 100644
--- a/apps/openmw/mwworld/refdata.cpp
+++ b/apps/openmw/mwworld/refdata.cpp
@@ -118,6 +118,11 @@ namespace MWWorld
         return mBaseNode;
     }
 
+    const SceneUtil::PositionAttitudeTransform* RefData::getBaseNode() const
+    {
+        return mBaseNode;
+    }
+
     int RefData::getCount() const
     {
         return mCount;
diff --git a/apps/openmw/mwworld/refdata.hpp b/apps/openmw/mwworld/refdata.hpp
index d02e05c98..28d2dad4c 100644
--- a/apps/openmw/mwworld/refdata.hpp
+++ b/apps/openmw/mwworld/refdata.hpp
@@ -75,6 +75,9 @@ namespace MWWorld
             /// Return base node (can be a null pointer).
             SceneUtil::PositionAttitudeTransform* getBaseNode();
 
+            /// Return base node (can be a null pointer).
+            const SceneUtil::PositionAttitudeTransform* getBaseNode() const;
+
             /// Set base node (can be a null pointer).
             void setBaseNode (SceneUtil::PositionAttitudeTransform* base);
 
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 357d50845..821f950dd 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -2317,7 +2317,7 @@ namespace MWWorld
         }
     }
 
-    bool World::getLOS(const MWWorld::Ptr& actor, const MWWorld::Ptr& targetActor)
+    bool World::getLOS(const MWWorld::ConstPtr& actor, const MWWorld::ConstPtr& targetActor)
     {
         if (!targetActor.getRefData().isEnabled() || !actor.getRefData().isEnabled())
             return false; // cannot get LOS unless both NPC's are enabled
diff --git a/apps/openmw/mwworld/worldimp.hpp b/apps/openmw/mwworld/worldimp.hpp
index 55932981e..51056c429 100644
--- a/apps/openmw/mwworld/worldimp.hpp
+++ b/apps/openmw/mwworld/worldimp.hpp
@@ -518,7 +518,7 @@ namespace MWWorld
             virtual void getItemsOwnedBy (const MWWorld::ConstPtr& npc, std::vector<MWWorld::Ptr>& out);
             ///< get all items in active cells owned by this Npc
 
-            virtual bool getLOS(const MWWorld::Ptr& actor,const MWWorld::Ptr& targetActor);
+            virtual bool getLOS(const MWWorld::ConstPtr& actor,const MWWorld::ConstPtr& targetActor);
             ///< get Line of Sight (morrowind stupid implementation)
 
             virtual float getDistToNearestRayHit(const osg::Vec3f& from, const osg::Vec3f& dir, float maxDist);