diff --git a/include/osgGA/TerrainManipulator b/include/osgGA/TerrainManipulator
index 756c8c958..6b7b9c636 100644
--- a/include/osgGA/TerrainManipulator
+++ b/include/osgGA/TerrainManipulator
@@ -27,6 +27,17 @@ class OSGGA_EXPORT TerrainManipulator : public MatrixManipulator
 
         virtual const char* className() const { return "Terrain"; }
 
+
+        enum RotationMode 
+        {
+            ELEVATION_AZIM_ROLL,
+            ELEVATION_AZIM,
+        };
+        
+        void setRotationMode(RotationMode mode);
+        RotationMode getRotationMode() const { return _rotationMode; }
+
+
         /** set the minimum distance (as ratio) the eye point can be zoomed in towards the
             center before the center is pushed forward.*/        
         void setMinimumZoomScale(float minimumZoomScale) { _minimumZoomScale=minimumZoomScale; }
@@ -34,6 +45,7 @@ class OSGGA_EXPORT TerrainManipulator : public MatrixManipulator
         /** get the minimum distance (as ratio) the eye point can be zoomed in */
         float getMinimumZoomScale() const { return _minimumZoomScale; }
 
+
         /** set the position of the matrix manipulator using a 4x4 Matrix.*/
         virtual void setByMatrix(const osg::Matrixd& matrix);
 
@@ -100,20 +112,26 @@ class OSGGA_EXPORT TerrainManipulator : public MatrixManipulator
             If speed is below a threshold then return false, otherwise return true.*/
         bool isMouseMoving();
 
+
+        void clampOrientation();
+
+
         // Internal event stack comprising last three mouse events.
         osg::ref_ptr<const GUIEventAdapter> _ga_t1;
         osg::ref_ptr<const GUIEventAdapter> _ga_t0;
 
-        osg::ref_ptr<osg::Node>       _node;
+        osg::ref_ptr<osg::Node> _node;
 
-        float _modelScale;
-        float _minimumZoomScale;
+        float                   _modelScale;
 
-        bool _thrown;
+        RotationMode            _rotationMode;
+        float                   _minimumZoomScale;
+
+        bool                    _thrown;
         
-        osg::CoordinateFrame _coordinateFrame;        
-        osg::Quat   _rotation;
-        float       _distance;
+        osg::CoordinateFrame    _coordinateFrame;        
+        osg::Quat               _rotation;
+        float                   _distance;
 
 };
 
diff --git a/src/osgGA/TerrainManipulator.cpp b/src/osgGA/TerrainManipulator.cpp
index 18b33b02d..863f0745a 100644
--- a/src/osgGA/TerrainManipulator.cpp
+++ b/src/osgGA/TerrainManipulator.cpp
@@ -9,10 +9,13 @@ using namespace osgGA;
 TerrainManipulator::TerrainManipulator()
 {
     _modelScale = 0.01f;
+    
+    _rotationMode =ELEVATION_AZIM; 
     _minimumZoomScale = 0.0005f;
+    _distance = 1.0f;
+
     _thrown = false;
 
-    _distance = 1.0f;
 }
 
 
@@ -21,6 +24,13 @@ TerrainManipulator::~TerrainManipulator()
 }
 
 
+void TerrainManipulator::setRotationMode(RotationMode mode)
+{
+    _rotationMode = mode;
+
+    // need to correct rotation.
+}
+
 void TerrainManipulator::setNode(osg::Node* node)
 {
     _node = node;
@@ -268,6 +278,8 @@ void TerrainManipulator::setByMatrix(const osg::Matrixd& matrix)
         }
     }    
 
+
+    clampOrientation();
 }
 
 osg::Matrixd TerrainManipulator::getMatrix() const
@@ -326,6 +338,8 @@ void TerrainManipulator::computePosition(const osg::Vec3& eye,const osg::Vec3& c
 
     rotation_matrix.get(_rotation);
     _rotation = _rotation.inverse();
+
+    clampOrientation();
 }
 
 
@@ -345,25 +359,50 @@ bool TerrainManipulator::calcMovement()
     if (buttonMask==GUIEventAdapter::LEFT_MOUSE_BUTTON)
     {
 
-        // rotate camera.
+        if (_rotationMode==ELEVATION_AZIM_ROLL)
+        {
+            // rotate camera.
+            osg::Vec3 axis;
+            float angle;
 
-        osg::Vec3 axis;
-        float angle;
+            float px0 = _ga_t0->getXnormalized();
+            float py0 = _ga_t0->getYnormalized();
 
-        float px0 = _ga_t0->getXnormalized();
-        float py0 = _ga_t0->getYnormalized();
+            float px1 = _ga_t1->getXnormalized();
+            float py1 = _ga_t1->getYnormalized();
+
+
+            trackball(axis,angle,px1,py1,px0,py0);
+
+            osg::Quat new_rotate;
+            new_rotate.makeRotate(angle,axis);
+
+            _rotation = _rotation*new_rotate;
+        }
+        else
+        {
+            osg::Matrix rotation_matrix;
+            rotation_matrix.set(_rotation);
+
+            osg::Vec3 lookVector = -getUpVector(rotation_matrix);
+            osg::Vec3 sideVector = getSideVector(rotation_matrix);
+            osg::Vec3 upVector = getFrontVector(rotation_matrix);
+
+            osg::Vec3 forwardVector =osg::Vec3(0.0f,0.0f,1.0f)^sideVector;
+            sideVector = forwardVector^osg::Vec3(0.0f,0.0f,1.0f);
+
+            forwardVector.normalize();
+            sideVector.normalize();
+            
+            osg::Quat rotate_elevation;
+            rotate_elevation.makeRotate(dy,sideVector);
+
+            osg::Quat rotate_azim;
+            rotate_azim.makeRotate(-dx,osg::Vec3(0.0f,0.0f,1.0f));
+            
+            _rotation = _rotation * rotate_elevation * rotate_azim;
+        }
         
-        float px1 = _ga_t1->getXnormalized();
-        float py1 = _ga_t1->getYnormalized();
-        
-
-        trackball(axis,angle,px1,py1,px0,py0);
-
-        osg::Quat new_rotate;
-        new_rotate.makeRotate(angle,axis);
-        
-        _rotation = _rotation*new_rotate;
-
         return true;
 
     }
@@ -457,6 +496,37 @@ bool TerrainManipulator::calcMovement()
     return false;
 }
 
+void TerrainManipulator::clampOrientation()
+{
+    if (_rotationMode==ELEVATION_AZIM)
+    {
+        osg::Matrix rotation_matrix;
+        rotation_matrix.set(_rotation);
+
+        osg::Vec3 lookVector = -getUpVector(rotation_matrix);
+        osg::Vec3 upVector = getFrontVector(rotation_matrix);
+
+        osg::Vec3 sideVector = lookVector ^ osg::Vec3(0.0f,0.0f,1.0f);
+
+        if (sideVector.length()<0.1)
+        {
+            osg::notify(osg::NOTICE)<<"Side vector short "<<sideVector.length()<<std::endl;
+
+            sideVector = upVector^osg::Vec3(0.0f,0.0f,1.0f);
+            sideVector.normalize();
+        
+        }
+
+        Vec3 newUpVector = sideVector^lookVector;
+        newUpVector.normalize();
+
+        osg::Quat rotate_roll;
+        rotate_roll.makeRotate(upVector,newUpVector);
+
+        _rotation = _rotation * rotate_roll;
+    }
+}
+
 
 /*
  * This size should really be based on the distance from the center of