diff --git a/include/osgUtil/Simplifier b/include/osgUtil/Simplifier
index dde718d10..6494a1dde 100644
--- a/include/osgUtil/Simplifier
+++ b/include/osgUtil/Simplifier
@@ -81,9 +81,13 @@ class OSGUTIL_EXPORT Simplifier : public osg::NodeVisitor
             }
         }
 
-        /** simply the geometry to defined ratio of original size.*/
+        /** simply the geometry.*/
         void simplify(osg::Geometry& geometry);
+        
+        typedef std::vector<unsigned int> IndexList; /// a list of point indices
 
+        /** simply the geometry, whilst protecting key points from being modified.*/
+        void simplify(osg::Geometry& geometry, const IndexList& protectedPoints);
 
     protected:
     
diff --git a/src/osgTerrain/DataSet.cpp b/src/osgTerrain/DataSet.cpp
index bdbd10d86..a6dbc16ee 100644
--- a/src/osgTerrain/DataSet.cpp
+++ b/src/osgTerrain/DataSet.cpp
@@ -1924,7 +1924,7 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         return 0;
     }
 
-    bool createSkirt = false;
+    bool createSkirt = true;
 
     // compute sizes.
     unsigned int numColumns = grid->getNumColumns();
@@ -2108,6 +2108,8 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
     if (n.valid() && n->size()!=numVertices) n->resize(numVertices);
 #endif
 
+    osgUtil::Simplifier::IndexList pointsToProtectDuringSimplification;
+
     if (numVerticesInSkirt>0)
     {
         osg::DrawElementsUShort& skirtDrawElements = *(new osg::DrawElementsUShort(GL_QUAD_STRIP,2*numVerticesInSkirt+2));
@@ -2118,8 +2120,15 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         r=0;
         for(c=0;c<numColumns-1;++c)
         {
+            // assign indices to primitive set
 	    skirtDrawElements[ei++] = (r)*numColumns+c;
 	    skirtDrawElements[ei++] = vi;
+            
+            // mark these points as protected to prevent them from being removed during simplification
+            pointsToProtectDuringSimplification.push_back((r)*numColumns+c);
+            pointsToProtectDuringSimplification.push_back(vi);
+            
+            // add in the new point on the bottom of the skirt
             v[vi] = v[(r)*numColumns+c]+skirtVector;
             if (n.valid()) (*n)[vi] = (*n)[r*numColumns+c];
             t[vi++] = t[(r)*numColumns+c];
@@ -2128,8 +2137,15 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         c=numColumns-1;
         for(r=0;r<numRows-1;++r)
         {
+            // assign indices to primitive set
 	    skirtDrawElements[ei++] = (r)*numColumns+c;
 	    skirtDrawElements[ei++] = vi;
+            
+            // mark these points as protected to prevent them from being removed during simplification
+            pointsToProtectDuringSimplification.push_back((r)*numColumns+c);
+            pointsToProtectDuringSimplification.push_back(vi);
+
+            // add in the new point on the bottom of the skirt
             v[vi] = v[(r)*numColumns+c]+skirtVector;
             if (n.valid()) (*n)[vi] = (*n)[(r)*numColumns+c];
             t[vi++] = t[(r)*numColumns+c];
@@ -2138,8 +2154,15 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         r=numRows-1;
         for(c=numColumns-1;c>0;--c)
         {
+            // assign indices to primitive set
 	    skirtDrawElements[ei++] = (r)*numColumns+c;
 	    skirtDrawElements[ei++] = vi;
+            
+            // mark these points as protected to prevent them from being removed during simplification
+            pointsToProtectDuringSimplification.push_back((r)*numColumns+c);
+            pointsToProtectDuringSimplification.push_back(vi);
+
+            // add in the new point on the bottom of the skirt
             v[vi] = v[(r)*numColumns+c]+skirtVector;
             if (n.valid()) (*n)[vi] = (*n)[(r)*numColumns+c];
             t[vi++] = t[(r)*numColumns+c];
@@ -2148,8 +2171,15 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         c=0;
         for(r=numRows-1;r>0;--r)
         {
+            // assign indices to primitive set
 	    skirtDrawElements[ei++] = (r)*numColumns+c;
 	    skirtDrawElements[ei++] = vi;
+            
+            // mark these points as protected to prevent them from being removed during simplification
+            pointsToProtectDuringSimplification.push_back((r)*numColumns+c);
+            pointsToProtectDuringSimplification.push_back(vi);
+
+            // add in the new point on the bottom of the skirt
             v[vi] = v[(r)*numColumns+c]+skirtVector;
             if (n.valid()) (*n)[vi] = (*n)[(r)*numColumns+c];
             t[vi++] = t[(r)*numColumns+c];
@@ -2179,18 +2209,12 @@ osg::Node* DataSet::DestinationTile::createPolygonal()
         geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
     }
     
-#if 1
     osgUtil::Simplifier simplifier(0.5f,geometry->getBound().radius()/2000.0f);
-//    osgUtil::Simplifier simplifier(1.0f,1.0f);
     
-    simplifier.simplify(*geometry);  // this will replace the normal vector with a new one
-#endif
+    simplifier.simplify(*geometry, pointsToProtectDuringSimplification);  // this will replace the normal vector with a new one
 
-#if 1
     osgUtil::TriStripVisitor tsv;
     tsv.stripify(*geometry);
-#endif
-
 
     osg::Geode* geode = new osg::Geode;
     geode->addDrawable(geometry);
diff --git a/src/osgUtil/Simplifier.cpp b/src/osgUtil/Simplifier.cpp
index 5375ad532..c3339a45e 100644
--- a/src/osgUtil/Simplifier.cpp
+++ b/src/osgUtil/Simplifier.cpp
@@ -56,7 +56,7 @@ public:
         
     ~EdgeCollapse();
 
-    void setGeometry(osg::Geometry* geometry);
+    void setGeometry(osg::Geometry* geometry, const Simplifier::IndexList& protectedPoints);
     osg::Geometry* getGeometry() { return _geometry; }
 
     unsigned int getNumOfTriangles() { return _triangleSet.size(); }
@@ -199,8 +199,10 @@ public:
 
     struct Point : public osg::Referenced
     {
-        Point():_index(0) {}
+        Point(): _protected(false), _index(0) {}
         
+        bool _protected;
+
         unsigned int _index;
 
         osg::Vec3           _vertex;
@@ -223,6 +225,8 @@ public:
         
         bool isBoundaryPoint() const
         {
+            if (_protected) return true;
+        
             for(TriangleSet::const_iterator itr=_triangles.begin();
                 itr!=_triangles.end();
                 ++itr)
@@ -1180,7 +1184,7 @@ class CopyVertexArrayToPointsVisitor : public osg::ArrayVisitor
         EdgeCollapse::PointList& _pointList;
 };
 
-void EdgeCollapse::setGeometry(osg::Geometry* geometry)
+void EdgeCollapse::setGeometry(osg::Geometry* geometry, const Simplifier::IndexList& protectedPoints)
 {
     _geometry = geometry;
     
@@ -1227,10 +1231,20 @@ void EdgeCollapse::setGeometry(osg::Geometry* geometry)
             geometry->getVertexAttribArray(vi)->accept(copyArrayToPoints);
     }
 
+    // now set the protected points up.
+    for(Simplifier::IndexList::const_iterator pitr=protectedPoints.begin();
+        pitr!=protectedPoints.end();
+        ++pitr)
+    {
+        _originalPointList[*pitr]->_protected = true;
+    }
+
+
     CollectTriangleIndexFunctor collectTriangles;
     collectTriangles.setEdgeCollapse(this);
     
     _geometry->accept(collectTriangles);
+    
 }
  
 
@@ -1466,11 +1480,20 @@ Simplifier::Simplifier(float sampleRatio, float maximumError):
 }
 
 void Simplifier::simplify(osg::Geometry& geometry)
+{
+    // pass an empty list of indices to simply(Geometry,IndexList)
+    // so that this one method handle both cases of non protected indices
+    // and specified indices.
+    IndexList emptyList;
+    simplify(geometry,emptyList);
+}
+
+void Simplifier::simplify(osg::Geometry& geometry, const IndexList& protectedPoints)
 {
     osg::notify(osg::WARN)<<"++++++++++++++simplifier************"<<std::endl;
 
     EdgeCollapse ec;
-    ec.setGeometry(&geometry);
+    ec.setGeometry(&geometry, protectedPoints);
 
     ec.updateErrorMetricForAllEdges();
 
@@ -1498,5 +1521,4 @@ void Simplifier::simplify(osg::Geometry& geometry)
     osg::notify(osg::WARN)<<           "        continueSimplification(,,)  = "<<continueSimplification((*ec._edgeSet.begin())->getErrorMetric() , numOriginalPrimitives, ec._triangleSet.size())<<std::endl;
     
     ec.copyBackToGeometry();
-
 }