diff --git a/include/osg/RefNodePath b/include/osg/RefNodePath
index bdef818cc..ee4d61a63 100644
--- a/include/osg/RefNodePath
+++ b/include/osg/RefNodePath
@@ -37,6 +37,27 @@ class RefNodePath : public NodeList
             }
         }
         
+        RefNodePath& operator = (const RefNodePath& rhs)
+        {
+            if (&rhs == this) return *this;
+            
+            NodeList::operator = (rhs);            
+            
+            return *this;
+        }
+        
+        RefNodePath& operator = (const NodePath& rhs)
+        {
+            for(osg::NodePath::const_iterator itr=rhs.begin();
+                itr != rhs.end();
+                ++itr)
+            {
+                push_back(*itr);
+            }
+            
+            return *this;
+        }
+
         inline operator NodePath () const
         {
             NodePath nodePath;
diff --git a/include/osg/Transform b/include/osg/Transform
index c20921053..aa9ef6979 100644
--- a/include/osg/Transform
+++ b/include/osg/Transform
@@ -27,21 +27,21 @@ namespace osg {
 
 /** compute the matrix which transforms objects in local coords to world coords,
   * by accumulating the Transform local to world matrices along the specified node path.*/
-extern SG_EXPORT Matrix computeLocalToWorld(NodePath& nodePath);
+extern SG_EXPORT Matrix computeLocalToWorld(const NodePath& nodePath);
 
 /** compute the matrix which transforms objects in world coords to local coords,
   * by accumulating the Transform world to local matrices along the specified node path.*/
-extern SG_EXPORT Matrix computeWorldToLocal(NodePath& nodePath);
+extern SG_EXPORT Matrix computeWorldToLocal(const NodePath& nodePath);
 
 /** compute the matrix which transforms objects in local coords to world coords,
   * by accumulating the Transform local to world matrices along the specified node path 
   * the supplied initialial camera modelview .*/
-extern SG_EXPORT Matrix computeLocalToEye(const Matrix& modelview, NodePath& nodePath);
+extern SG_EXPORT Matrix computeLocalToEye(const Matrix& modelview, const NodePath& nodePath);
 
 /** compute the matrix which transforms objects in world coords to local coords,
   * by accumulating the Transform world to local matrices along the specified node path 
   * the inverse of the supplied initialial camera modelview.*/
-extern SG_EXPORT Matrix computeEyeToLocal(const Matrix& modelview, NodePath& nodePath);
+extern SG_EXPORT Matrix computeEyeToLocal(const Matrix& modelview, const NodePath& nodePath);
 
 
 /** A Transform is a group node for which all children are transformed by
diff --git a/include/osgGA/NodeTrackerManipulator b/include/osgGA/NodeTrackerManipulator
index 1a0199e8a..9ac1f4f99 100644
--- a/include/osgGA/NodeTrackerManipulator
+++ b/include/osgGA/NodeTrackerManipulator
@@ -15,7 +15,9 @@
 #define OSGGA_NODETRACKERMANIPULATOR 1
 
 #include <osgGA/MatrixManipulator>
+
 #include <osg/Quat>
+#include <osg/RefNodePath>
 
 namespace osgGA{
 
@@ -27,10 +29,15 @@ class OSGGA_EXPORT NodeTrackerManipulator : public MatrixManipulator
 
         virtual const char* className() const { return "NodeTrackerManipulator"; }
 
-        void setTrackNode(osg::Node* node) { _trackNode = node; }
-        osg::Node* getTrackNode() { return _trackNode.get(); }
-        const osg::Node* getTrackNode() const { return _trackNode.get(); }
+        void setTrackNodePath(const osg::RefNodePath& nodePath) { _trackNodePath = nodePath; }
+        void setTrackNodePath(const osg::NodePath& nodePath) { _trackNodePath = nodePath; }
 
+        osg::RefNodePath& getTrackNodePath() { return _trackNodePath; }
+        const osg::RefNodePath& getTrackNodePath() const { return _trackNodePath; }
+
+        void setTrackNode(osg::Node* node);
+        osg::Node* getTrackNode() { return _trackNodePath.empty() ? 0 : _trackNodePath.back().get(); }
+        const osg::Node* getTrackNode() const { return _trackNodePath.empty() ? 0 : _trackNodePath.back().get(); }
 
         enum TrackerMode 
         {
@@ -99,6 +106,21 @@ class OSGGA_EXPORT NodeTrackerManipulator : public MatrixManipulator
     protected:
 
         virtual ~NodeTrackerManipulator();
+        
+        inline bool validateNodePath() const
+        {
+            if (!_trackNodePath.valid())
+            {
+                if (_trackNodePath.empty())
+                {
+                    osg::notify(osg::NOTICE)<<"Warning: tracked node path has been invalidated by changes in the scene graph."<<std::endl;
+                    NodeTrackerManipulator* non_const_this = const_cast<NodeTrackerManipulator*>(this);
+                    non_const_this->_trackNodePath.clear();
+                }
+                return false;
+            }
+            return true;
+        }
 
         /** Reset the internal GUIEvent stack.*/
         void flushMouseEventStack();
@@ -133,7 +155,8 @@ class OSGGA_EXPORT NodeTrackerManipulator : public MatrixManipulator
         osg::ref_ptr<const GUIEventAdapter> _ga_t0;
 
         osg::ref_ptr<osg::Node> _node;
-        osg::ref_ptr<osg::Node> _trackNode;
+        
+        osg::RefNodePath        _trackNodePath;
 
         TrackerMode             _trackerMode;
         RotationMode            _rotationMode;
diff --git a/src/osg/Transform.cpp b/src/osg/Transform.cpp
index 7caeea81f..269da8838 100644
--- a/src/osg/Transform.cpp
+++ b/src/osg/Transform.cpp
@@ -46,10 +46,11 @@ class TransformVisitor : public NodeVisitor
             }
         }
         
-        void accumulate(NodePath& nodePath)
+        void accumulate(const NodePath& nodePath)
         {
-            for(NodePath::iterator itr=nodePath.begin();
-                itr!=nodePath.end();
+            NodePath& non_const_nodePath = const_cast<NodePath&>(nodePath);
+            for(NodePath::iterator itr=non_const_nodePath.begin();
+                itr!=non_const_nodePath.end();
                 ++itr)
             {
                 (*itr)->accept(*this);
@@ -58,7 +59,7 @@ class TransformVisitor : public NodeVisitor
     
 };
 
-Matrix osg::computeLocalToWorld(NodePath& nodePath)
+Matrix osg::computeLocalToWorld(const NodePath& nodePath)
 {
     Matrix matrix;
     TransformVisitor tv(matrix,TransformVisitor::LOCAL_TO_WORLD);
@@ -66,7 +67,7 @@ Matrix osg::computeLocalToWorld(NodePath& nodePath)
     return matrix;
 }
 
-Matrix osg::computeWorldToLocal(NodePath& nodePath)
+Matrix osg::computeWorldToLocal(const NodePath& nodePath)
 {
     osg::Matrix matrix;
     TransformVisitor tv(matrix,TransformVisitor::WORLD_TO_LOCAL);
@@ -74,7 +75,7 @@ Matrix osg::computeWorldToLocal(NodePath& nodePath)
     return matrix;
 }
 
-Matrix osg::computeLocalToEye(const Matrix& modelview,NodePath& nodePath)
+Matrix osg::computeLocalToEye(const Matrix& modelview,const NodePath& nodePath)
 {
     Matrix matrix(modelview);
     TransformVisitor tv(matrix,TransformVisitor::LOCAL_TO_WORLD);
@@ -82,7 +83,7 @@ Matrix osg::computeLocalToEye(const Matrix& modelview,NodePath& nodePath)
     return matrix;
 }
 
-Matrix osg::computeEyeToLocal(const Matrix& modelview,NodePath& nodePath)
+Matrix osg::computeEyeToLocal(const Matrix& modelview,const NodePath& nodePath)
 {
     Matrix matrix;
     matrix.invert(modelview);
diff --git a/src/osgGA/NodeTrackerManipulator.cpp b/src/osgGA/NodeTrackerManipulator.cpp
index f3ecb9c58..470127b24 100644
--- a/src/osgGA/NodeTrackerManipulator.cpp
+++ b/src/osgGA/NodeTrackerManipulator.cpp
@@ -72,6 +72,16 @@ void NodeTrackerManipulator::setNode(osg::Node* node)
     if (getAutoComputeHomePosition()) computeHomePosition();    
 }
 
+void NodeTrackerManipulator::setTrackNode(osg::Node* node)
+{
+    CollectParentPaths cpp;
+    node->accept(cpp);
+
+    if (!cpp._nodePaths.empty())
+    {
+        _trackNodePath = cpp._nodePaths[0];
+    }
+}
 
 const osg::Node* NodeTrackerManipulator::getNode() const
 {
@@ -321,32 +331,19 @@ void NodeTrackerManipulator::setByMatrix(const osg::Matrixd& matrix)
 
 void NodeTrackerManipulator::computeNodeWorldToLocal(osg::Matrixd& worldToLocal) const
 {
-    if (_trackNode.valid())
+    if (validateNodePath())
     {
-        CollectParentPaths cpp;
-        NodeTrackerManipulator* non_const_this = const_cast<NodeTrackerManipulator*>(this);
-        non_const_this->_trackNode->accept(cpp);
-
-        if (!cpp._nodePaths.empty())
-        {
-            worldToLocal = osg::computeWorldToLocal(cpp._nodePaths[0]);
-        }
+        worldToLocal = osg::computeWorldToLocal(_trackNodePath);
     }
 }
 
 void NodeTrackerManipulator::computeNodeLocalToWorld(osg::Matrixd& localToWorld) const
 {
-    if (_trackNode.valid())
+    if (validateNodePath())
     {
-        CollectParentPaths cpp;
-        NodeTrackerManipulator* non_const_this = const_cast<NodeTrackerManipulator*>(this);
-        non_const_this->_trackNode->accept(cpp);
-
-        if (!cpp._nodePaths.empty())
-        {
-            localToWorld = osg::computeLocalToWorld(cpp._nodePaths[0]);
-        }
+        localToWorld = osg::computeLocalToWorld(_trackNodePath);
     }
+
 }
 
 void NodeTrackerManipulator::computeNodeCenterAndRotation(osg::Vec3d& nodeCenter, osg::Quat& nodeRotation) const
@@ -354,8 +351,8 @@ void NodeTrackerManipulator::computeNodeCenterAndRotation(osg::Vec3d& nodeCenter
     osg::Matrixd localToWorld;
     computeNodeLocalToWorld(localToWorld);
     
-    if (_trackNode.valid())
-        nodeCenter = _trackNode->getBound().center()*localToWorld;
+    if (validateNodePath())
+        nodeCenter = _trackNodePath.back()->getBound().center()*localToWorld;
     else
         nodeCenter = osg::Vec3d(0.0f,0.0f,0.0f)*localToWorld;
 
@@ -482,25 +479,13 @@ bool NodeTrackerManipulator::calcMovement()
     if (dx==0 && dy==0) return false;
 
 
-    if (_trackNode.valid())
+    if (validateNodePath())
     {
-        // osg::notify(osg::NOTICE)<<"_trackNode="<<_trackNode->getName()<<std::endl;
+        osg::Matrix localToWorld;
+        localToWorld = osg::computeLocalToWorld(_trackNodePath);
 
-        CollectParentPaths cpp;
-        _trackNode->accept(cpp);
-
-        // osg::notify(osg::NOTICE)<<"number of nodepaths = "<<cpp._nodePaths.size()<<std::endl;
-        
-        if (!cpp._nodePaths.empty())
-        {
-            osg::Matrix localToWorld;
-            localToWorld = osg::computeLocalToWorld(cpp._nodePaths[0]);
-            
-            _center = _trackNode->getBound().center() * localToWorld;
-
-            
-        }
-    }        
+        _center = _trackNodePath.back()->getBound().center() * localToWorld;
+    }
 
     unsigned int buttonMask = _ga_t1->getButtonMask();
     if (buttonMask==GUIEventAdapter::LEFT_MOUSE_BUTTON)