diff --git a/include/osgTerrain/Terrain b/include/osgTerrain/Terrain
index 7a5553f66..e30888d21 100644
--- a/include/osgTerrain/Terrain
+++ b/include/osgTerrain/Terrain
@@ -36,17 +36,6 @@ class OSGTERRAIN_EXPORT Terrain : public osg::Group
 
         virtual void traverse(osg::NodeVisitor& nv);
         
-
-        /** Set the TerrainTechnique that is used as the prototype for all Terrain below the Terrain. */
-        void setTerrainTechnique(osgTerrain::TerrainTechnique* TerrainTechnique);
-
-        /** Get the TerrainTechnique*/
-        TerrainTechnique* getTerrainTechnique() { return _terrainTechnique.get(); }
-        
-        /** Get the const TerrainTechnique*/
-        const TerrainTechnique* getTerrainTechnique() const { return _terrainTechnique.get(); }
-
-
         /** Get the TerrainTile for a given TileID.*/
         TerrainTile* getTile(const TileID& tileID);
 
@@ -65,11 +54,9 @@ class OSGTERRAIN_EXPORT Terrain : public osg::Group
         typedef std::map< TileID, TerrainTile* >    TerrainTileMap;
         typedef std::set< TerrainTile* >            TerrainTileSet;
 
-        osg::ref_ptr<TerrainTechnique>      _terrainTechnique;
-        
-
-        TerrainTileSet                        _terrainTileSet;
-        TerrainTileMap                        _terrainTileMap;
+        mutable OpenThreads::Mutex          _mutex;
+        TerrainTileSet                      _terrainTileSet;
+        TerrainTileMap                      _terrainTileMap;
         
 
        
diff --git a/include/osgTerrain/TerrainTechnique b/include/osgTerrain/TerrainTechnique
index 239443934..d5dbe5d13 100644
--- a/include/osgTerrain/TerrainTechnique
+++ b/include/osgTerrain/TerrainTechnique
@@ -11,8 +11,8 @@
  * OpenSceneGraph Public License for more details.
 */
 
-#ifndef OSGTERRAIN_terrainTileTECHNIQUE
-#define OSGTERRAIN_terrainTileTECHNIQUE 1
+#ifndef OSGTERRAIN_TERRAINTECHNIQUE
+#define OSGTERRAIN_TERRAINTECHNIQUE 1
 
 #include <osg/Object>
 
diff --git a/src/osgTerrain/Terrain.cpp b/src/osgTerrain/Terrain.cpp
index 16816fe04..3e248d4e7 100644
--- a/src/osgTerrain/Terrain.cpp
+++ b/src/osgTerrain/Terrain.cpp
@@ -12,6 +12,7 @@
 */
 
 #include <osgTerrain/Terrain>
+#include <OpenThreads/ScopedLock>
 
 using namespace osg;
 using namespace osgTerrain;
@@ -20,8 +21,16 @@ Terrain::Terrain()
 {
 }
 
+Terrain::Terrain(const Terrain& ts, const osg::CopyOp& copyop):
+    osg::Group(ts,copyop)
+{
+}
+
+
 Terrain::~Terrain()
 {
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
     for(TerrainTileSet::iterator itr = _terrainTileSet.begin();
         itr != _terrainTileSet.end();
         ++itr)
@@ -33,10 +42,6 @@ Terrain::~Terrain()
     _terrainTileMap.clear();
 }
 
-Terrain::Terrain(const Terrain& ts, const osg::CopyOp& copyop)
-{
-}
-
 void Terrain::traverse(osg::NodeVisitor& nv)
 {
     Group::traverse(nv);
@@ -44,6 +49,8 @@ void Terrain::traverse(osg::NodeVisitor& nv)
 
 TerrainTile* Terrain::getTile(const TileID& tileID)
 {
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
     TerrainTileMap::iterator itr = _terrainTileMap.find(tileID);
     if (itr != _terrainTileMap.end()) return 0;
     
@@ -52,15 +59,20 @@ TerrainTile* Terrain::getTile(const TileID& tileID)
 
 const TerrainTile* Terrain::getTile(const TileID& tileID) const
 {
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
     TerrainTileMap::const_iterator itr = _terrainTileMap.find(tileID);
     if (itr != _terrainTileMap.end()) return 0;
     
     return itr->second;
 }
 
+static unsigned int s_maxNumTiles = 0;
 void Terrain::registerTerrainTile(TerrainTile* tile)
 {
     if (!tile) return;
+
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
     
     if (tile->getTileID().valid())
     {
@@ -69,13 +81,17 @@ void Terrain::registerTerrainTile(TerrainTile* tile)
     
     _terrainTileSet.insert(tile);
 
-    osg::notify(osg::INFO)<<"Terrain::registerTerrainTile "<<tile<<" total number of tile "<<_terrainTileSet.size()<<std::endl;
+    if (_terrainTileSet.size() > s_maxNumTiles) s_maxNumTiles = _terrainTileSet.size();
+
+    // osg::notify(osg::NOTICE)<<"Terrain::registerTerrainTile "<<tile<<" total number of tile "<<_terrainTileSet.size()<<" max = "<<s_maxNumTiles<<std::endl;
 }
 
 void Terrain::unregisterTerrainTile(TerrainTile* tile)
 {
     if (!tile) return;
 
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
     if (tile->getTileID().valid())
     {
         _terrainTileMap.erase(tile->getTileID());
@@ -83,5 +99,5 @@ void Terrain::unregisterTerrainTile(TerrainTile* tile)
     
     _terrainTileSet.erase(tile);
 
-    osg::notify(osg::INFO)<<"Terrain::unregisterTerrainTile "<<tile<<" total number of tile "<<_terrainTileSet.size()<<std::endl;
+    // osg::notify(osg::NOTICE)<<"Terrain::unregisterTerrainTile "<<tile<<" total number of tile "<<_terrainTileSet.size()<<" max = "<<s_maxNumTiles<<std::endl;
 }