diff --git a/owlps-positioning/src/accesspoint.cc b/owlps-positioning/src/accesspoint.cc
index 025f8a3..e6fb4d0 100644
--- a/owlps-positioning/src/accesspoint.cc
+++ b/owlps-positioning/src/accesspoint.cc
@@ -5,6 +5,18 @@ using namespace std ;
 
 
 
+/* *** Operations *** */
+
+
+double AccessPoint::friis_constant_term() const
+{
+  double wavelength =
+    static_cast<double>(PosUtil::LIGHT_SPEED) / frequency ;
+  return antenna_gain + 20 * log10(wavelength) - 20 * log10(4 * M_PI) ;
+}
+
+
+
 /* *** Operators *** */
 
 
diff --git a/owlps-positioning/src/accesspoint.hh b/owlps-positioning/src/accesspoint.hh
index 7c3ab70..d42ea99 100644
--- a/owlps-positioning/src/accesspoint.hh
+++ b/owlps-positioning/src/accesspoint.hh
@@ -67,6 +67,12 @@ public:
   void set_friis_index(const float _friis_index) ;
   //@}
 
+  /** @name Operations */
+  //@{
+  /// Returns the Friis formula's constant term
+  double friis_constant_term(void) const ;
+  //@}
+
   /** @name Operators */
   //@{
   AccessPoint& operator=(const AccessPoint &source) ;