diff --git a/owlps-positioning/src/stock.cc b/owlps-positioning/src/stock.cc
index 94c4137..158c3f8 100644
--- a/owlps-positioning/src/stock.cc
+++ b/owlps-positioning/src/stock.cc
@@ -239,6 +239,17 @@ void Stock::update_all_friis_indexes()
 }
 
 
+double Stock::ap_matrix_get_ss(const std::string &mac_transmitter,
+                               const std::string &mac_receiver)
+{
+  const AccessPoint &receiver = get_ap(mac_receiver) ;
+  const ReferencePoint &rp =
+    get_reference_point(receiver.get_coordinates()) ;
+
+  return rp.average_measurements(mac_transmitter) ;
+}
+
+
 
 /* *** ReferencePoint operations *** */
 
diff --git a/owlps-positioning/src/stock.hh b/owlps-positioning/src/stock.hh
index a22e088..86f4f1d 100644
--- a/owlps-positioning/src/stock.hh
+++ b/owlps-positioning/src/stock.hh
@@ -93,6 +93,8 @@ public:
   static AccessPoint& getw_ap(const std::string &mac) ;
   /// Updates the friis indexes of all the APs
   static void update_all_friis_indexes(void) ;
+  static double ap_matrix_get_ss(const std::string &mac_transmitter,
+                                 const std::string &mac_receiver) ;
   //@}
 
   /** @name ReferencePoint operations */