diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_grid_generator.h b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_grid_generator.h
index 25e790ec012..5a955dc6887 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_grid_generator.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_grid_generator.h
@@ -23,13 +23,7 @@
 * Definition of the Arr_grid_landmarks_generator<Arrangement> template.
 */
 
-#include <CGAL/Arr_observer.h>
-#include <CGAL/Arrangement_2/Arr_traits_adaptor_2.h>
-#include <CGAL/Arr_batched_point_location.h>
-
-#include <list>
-#include <algorithm>
-#include <vector>
+#include <CGAL/Arr_point_location/Arr_lm_generator_base.h>
 
 CGAL_BEGIN_NAMESPACE
 
@@ -37,14 +31,22 @@ CGAL_BEGIN_NAMESPACE
  * A generator for the landmarks point-locatoion class, which uses a
  * set of points on a grid as its set of landmarks.
 */
-template <class Arrangement_>
+template <class Arrangement_,
+          class Nearest_neighbor_  =
+            Arr_landmarks_nearest_neighbor<typename
+                                           Arrangement_::Geometry_traits_2> >
 class Arr_grid_landmarks_generator :
-    public Arr_observer <Arrangement_>
+    public Arr_landmarks_generator_base<Arrangement_, Nearest_neighbor_>
 {
 public:
 
   typedef Arrangement_                                      Arrangement_2;
-  typedef Arr_grid_landmarks_generator<Arrangement_2>       Self;
+  typedef Nearest_neighbor_                                 Nearest_neighbor;
+
+  typedef Arr_landmarks_generator_base<Arrangement_2,
+                                       Nearest_neighbor>    Base;
+  typedef Arr_grid_landmarks_generator<Arrangement_2,
+                                       Nearest_neighbor>    Self;
 
   typedef typename Arrangement_2::Geometry_traits_2     Geometry_traits_2;
   typedef typename Arrangement_2::Vertex_const_iterator Vertex_const_iterator;
@@ -63,7 +65,7 @@ public:
 
 protected:
 
-  typedef std::vector<Point_2>                           Points_set;
+  typedef typename Base::Points_set                     Points_set;
   typedef std::pair<Point_2,CGAL::Object>                PL_pair;
   typedef std::vector<PL_pair>                           Pairs_set;
 
@@ -98,7 +100,7 @@ public:
     /*! Constructor. */
 
   Arr_grid_landmarks_generator (const Arrangement_2& arr) :
-    Arr_observer<Arrangement_2> (const_cast<Arrangement_2 &>(arr)),
+    Base (arr),
     ignore_notifications (false),
     updated (false),
     num_landmarks (0),
@@ -110,7 +112,7 @@ public:
 
   Arr_grid_landmarks_generator (const Arrangement_2& arr,
                                 unsigned int n_landmarks) :
-    Arr_observer<Arrangement_2> (const_cast<Arrangement_2 &>(arr)),
+    Base (arr),
     ignore_notifications (false),
     updated (false),
     num_landmarks (n_landmarks),
diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_halton_generator.h b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_halton_generator.h
index 11814af5702..7796c065e1b 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_halton_generator.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_halton_generator.h
@@ -50,7 +50,7 @@ public:
                                          Nearest_neighbor>  Self;
 
   typedef typename Arrangement_2::Point_2               Point_2;
-  typedef std::vector<Point_2>                          Points_set;
+  typedef typename Base::Points_set                     Points_set;
 
   typedef typename Arrangement_2::Vertex_const_iterator
                                                 Vertex_const_iterator;
diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_middle_edges_generator.h b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_middle_edges_generator.h
index 7481a4eabab..ea67078f937 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_middle_edges_generator.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_middle_edges_generator.h
@@ -23,7 +23,7 @@
 * Definition of the Arr_middle_edges_landmarks_generator<Arrangement> template.
 */
 
-#include <CGAL/Arr_point_location/Arr_lm_generator.h>
+#include <CGAL/Arr_point_location/Arr_lm_generator_base.h>
 
 CGAL_BEGIN_NAMESPACE
 
@@ -40,13 +40,13 @@ template <class Arrangement_,
           class Nearest_neighbor_ 
           = Arr_landmarks_nearest_neighbor <typename Arrangement_::Traits_2> >
 class Arr_middle_edges_landmarks_generator 
-  : public Arr_landmarks_generator <Arrangement_, Nearest_neighbor_>
+  : public Arr_landmarks_generator_base <Arrangement_, Nearest_neighbor_>
 {
 public:
   typedef Arrangement_					  Arrangement_2;
   typedef Arr_middle_edges_landmarks_generator<Arrangement_2, 
                                                Nearest_neighbor_>    Self;
-  typedef Arr_landmarks_generator<Arrangement_2, Nearest_neighbor_>  Base;
+  typedef Arr_landmarks_generator_base<Arrangement_2, Nearest_neighbor_>  Base;
 
   typedef typename Arrangement_2::Traits_2		Traits_2;
   typedef typename Arrangement_2::Edge_const_iterator	Edge_const_iterator;
@@ -78,11 +78,10 @@ public:
   /*! Constructor. */
   Arr_middle_edges_landmarks_generator 
   (const Arrangement_2& arr, int /* lm_num */ = -1) : 
-    Arr_landmarks_generator<Arrangement_2, Nearest_neighbor_> (arr)
+    Base (arr)
   {
-    CGAL_PRINT_DEBUG("Arr_middle_edges_landmarks_generator constructor.");
-    
-    this->build_landmarks_set();
+    //CGAL_PRINT_DEBUG("Arr_middle_edges_landmarks_generator constructor.");
+    this->build_landmark_set();
   }
   
   //Observer functions that should be empty, because they
@@ -107,8 +106,7 @@ protected:
    */
   virtual void _create_nn_points_set (NN_Points_set &nn_points) 
   {
-    CGAL_PRINT_DEBUG("create_middle_edges_points_list");
-
+    //CGAL_PRINT_DEBUG("create_middle_edges_points_list");
     Edge_const_iterator    eit;
     Halfedge_const_handle  hh;
     Arrangement_2 *arr = this->arrangement();
@@ -132,7 +130,7 @@ protected:
       const Point_2& p2 = hh->target()->point();
       Point_2 p ((p1.x()+p2.x())/2, (p1.y()+p2.y())/2);
       
-      CGAL_PRINT_DEBUG("mid point is= " << p);
+      //CGAL_PRINT_DEBUG("mid point is= " << p);
       
       CGAL::Object obj = CGAL::make_object(hh); 
       NN_Point_2 np(p, obj); 
diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_random_generator.h b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_random_generator.h
index 78622438914..c12e796251d 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_random_generator.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_random_generator.h
@@ -51,7 +51,7 @@ public:
                                          Nearest_neighbor>  Self;
 
   typedef typename Arrangement_2::Point_2               Point_2;
-  typedef std::vector<Point_2>                          Points_set;
+  typedef typename Base::Points_set                     Points_set;
 
   typedef typename Arrangement_2::Vertex_const_iterator
                                                 Vertex_const_iterator;
diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_vertices_generator.h b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_vertices_generator.h
index 67ea919175d..18431968fee 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_vertices_generator.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_point_location/Arr_lm_vertices_generator.h
@@ -23,10 +23,7 @@
  * Definition of the Arr_landmarks_vertices_generator<Arrangement> template.
  */
 
-#include <list>
-#include <CGAL/Arr_observer.h>
-#include <CGAL/Arrangement_2/Arr_traits_adaptor_2.h>
-#include <CGAL/Arr_point_location/Arr_lm_nearest_neighbor.h>
+#include <CGAL/Arr_point_location/Arr_lm_generator_base.h>
 
 CGAL_BEGIN_NAMESPACE
 
@@ -39,7 +36,7 @@ template <class Arrangement_,
             Arr_landmarks_nearest_neighbor<typename
                                            Arrangement_::Geometry_traits_2> >
 class Arr_landmarks_vertices_generator :
-    public Arr_observer<Arrangement_>
+    public Arr_landmarks_generator_base<Arrangement_, Nearest_neighbor_>
 {
 public:
 
@@ -47,6 +44,8 @@ public:
   typedef typename Arrangement_2::Geometry_traits_2     Geometry_traits_2;
   typedef Nearest_neighbor_                             Nearest_neighbor;
 
+  typedef Arr_landmarks_generator_base<Arrangement_2,
+                                       Nearest_neighbor>      Base;
   typedef Arr_landmarks_vertices_generator<Arrangement_2,
                                            Nearest_neighbor>  Self;
   
@@ -61,6 +60,8 @@ public:
   typedef typename Arrangement_2::Point_2               Point_2;
   typedef typename Arrangement_2::X_monotone_curve_2    X_monotone_curve_2;
 
+  typedef typename Base::Points_set                     Points_set;
+
   typedef typename Nearest_neighbor::NN_Point_2         NN_Point_2;
   typedef std::list<NN_Point_2>                         NN_Point_list;
 
@@ -88,7 +89,7 @@ public:
 
   /*! Constructor. */
   Arr_landmarks_vertices_generator (const Arrangement_2& arr) :
-    Arr_observer<Arrangement_2> (const_cast<Arrangement_2 &>(arr)),
+    Base (arr),
     ignore_notifications (false),
     updated (false),
     num_small_not_updated_changes(0),
@@ -98,6 +99,12 @@ public:
     build_landmark_set();
   }
 
+  virtual void _create_points_set (Points_set & /* points */)
+  {
+    std::cerr << "should not reach here!"<< std::endl;
+    CGAL_error();
+  }
+
   /*!
    * Creates the landmark set, using all arrangement vertices.
    */
diff --git a/Arrangement_on_surface_2/test/Arrangement_on_surface_2/point_location.cpp b/Arrangement_on_surface_2/test/Arrangement_on_surface_2/point_location.cpp
index ec3876ad7e8..a19f0903885 100644
--- a/Arrangement_on_surface_2/test/Arrangement_on_surface_2/point_location.cpp
+++ b/Arrangement_on_surface_2/test/Arrangement_on_surface_2/point_location.cpp
@@ -29,6 +29,8 @@
 #include <CGAL/Arr_point_location/Arr_lm_random_generator.h>
 #include <CGAL/Arr_point_location/Arr_lm_grid_generator.h>
 #include <CGAL/Arr_point_location/Arr_lm_halton_generator.h>
+#include <CGAL/Arr_point_location/Arr_lm_middle_edges_generator.h>
+//#include <CGAL/Arr_triangulation_point_location.h>
 
 typedef CGAL::Cartesian<Number_type>                    Kernel;
 typedef CGAL::Arr_segment_traits_2<Kernel>              Traits_2;
@@ -61,6 +63,12 @@ typedef CGAL::Arr_halton_landmarks_generator<Arrangement_2>
                                                     Halton_lm_generator;
 typedef CGAL::Arr_landmarks_point_location<Arrangement_2, Halton_lm_generator> 
                                                     Lm_halton_point_location;
+typedef CGAL::Arr_middle_edges_landmarks_generator<Arrangement_2>
+                                                    Middle_edges_generator;
+typedef CGAL::Arr_landmarks_point_location<Arrangement_2, Middle_edges_generator> 
+                                                    Lm_middle_edges_point_location;
+//typedef CGAL::Arr_triangulation_point_location<Arrangement_2> 
+//                                                    Lm_triangulation_point_location;
 
 // ===> Add new point location type here <===
 
@@ -72,7 +80,7 @@ typedef Objects_vector::iterator                          Object_iterator;
 
 // ===> Change the number of point-location startegies
 //      when a new point location is added. <===
-#define NUM_OF_POINT_LOCATION_STRATEGIES 7
+#define NUM_OF_POINT_LOCATION_STRATEGIES 8
 
 /*! */
 int check_point_location (Arrangement_2 &arr, Points_list &plist)
@@ -108,6 +116,18 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
   timer.stop(); 
   std::cout << "Halton lm construction took " << timer.time() <<std::endl;
 
+  timer.reset(); timer.start();
+  Middle_edges_generator             middle_edges_g(arr);
+  Lm_middle_edges_point_location        middle_edges_lm_pl (arr, &middle_edges_g);  // 7
+  timer.stop(); 
+  std::cout << "Middle edges lm construction took " << timer.time() <<std::endl;
+
+/*
+  timer.reset(); timer.start();
+  Lm_triangulation_point_location        triangulation_lm_pl (arr);  // 8
+  timer.stop(); 
+  std::cout << "Triangulation lm construction took " << timer.time() <<std::endl;
+*/
   std::cout << std::endl;
 
   // ===> Add new point location instance here. <===
@@ -205,6 +225,30 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
   timer.stop(); ///END
   std::cout << "Halton LM location took " << timer.time() <<std::endl;
 
+  timer.reset(); 
+  timer.start(); //START
+  for (piter = plist.begin(); piter != plist.end(); piter++ )
+  {
+    q = (*piter);
+    obj = middle_edges_lm_pl.locate (q);
+    objs[7].push_back(obj);
+  }
+  timer.stop(); ///END
+  std::cout << "Middle edges LM location took " << timer.time() <<std::endl;
+
+/*
+  timer.reset(); 
+  timer.start(); //START
+  for (piter = plist.begin(); piter != plist.end(); piter++ )
+  {
+    q = (*piter);
+    obj = triangulation_lm_pl.locate (q);
+    objs[8].push_back(obj);
+  }
+  timer.stop(); ///END
+  std::cout << "Triangulation LM location took " << timer.time() <<std::endl;
+*/
+
   std::cout << std::endl;
 
   // ===> Add a call to operate the the new point location. <===
@@ -219,7 +263,7 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
   {
     ob_iter[pl_index] = objs[pl_index].begin();
   }
-   
+
   //get size of objects
   unsigned int size = objs[0].size();
   //std::cout <<"size is "<< size << std::endl;
@@ -240,7 +284,7 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
   {
     //assign object to a face
     if (CGAL::assign (fh_ref, ob_iter[0][qi]))
-    {    
+    {
       for (int pl_index=1; pl_index<pls_num; pl_index++)
       {
         if (! CGAL::assign(fh_curr, ob_iter[pl_index][qi]))
@@ -264,7 +308,7 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
         {
           std::cout << "Error: point location number " 
             << pl_index << " return a different face"<< std::endl;
-          result = -1;         
+          result = -1;
         }
       }  
       //if (fh_ref->is_unbounded())
@@ -301,9 +345,9 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
           std::cout << "Error: point location number " 
             << pl_index << " return a different halfedge"<< std::endl;
           std::cout << "Halfedge (curr): "<< hh_curr->curve() << std::endl;
-          result = -1;         
+          result = -1;
         }
-      }      
+      }
     }
 
     //assign object to a vertex
@@ -332,12 +376,12 @@ int check_point_location (Arrangement_2 &arr, Points_list &plist)
         {
           std::cout << "Error: point location number " 
             << pl_index << " return a different vertex"<< std::endl;
-          result = -1;         
+          result = -1;
         }
       }
       std::cout << "Vertex: "<< vh_ref->point() << std::endl;
     }
-   
+
     else
     {
       std::cout << "Illegal point-location result." << std::endl;