diff --git a/owlps-positioning/src/interlinknetworks.cc b/owlps-positioning/src/interlinknetworks.cc
index 21ba497..7f6daea 100644
--- a/owlps-positioning/src/interlinknetworks.cc
+++ b/owlps-positioning/src/interlinknetworks.cc
@@ -1,26 +1,11 @@
 #include "interlinknetworks.hh"
-#include "mobile.hh"
-
-using std::tr1::unordered_map ;
 
 
 
-float InterlinkNetworks::estimate_distance(const Measurement &measurement)
+float InterlinkNetworks::
+estimate_distance(const Measurement &measurement)
 {
-  assert(request) ;
-
-  const AccessPoint &ap = *measurement.get_ap() ;
-  assert(&ap) ;
-
-  double constant_term =
-    ap.get_trx_power() +
-    ap.get_antenna_gain() +
-    20 * log10(
-      300000000.0 /
-      ap.get_frequency() /
-      (4 * M_PI)
-    ) +
-    request->get_mobile()->get_antenna_gain() ;
+  double constant_term = make_constant_term(measurement) ;
   const float &average_ss = measurement.get_average_ss() ;
   return pow(10, (constant_term - average_ss) / 35) ;
 }
diff --git a/owlps-positioning/src/multilaterationalgorithm.cc b/owlps-positioning/src/multilaterationalgorithm.cc
index 3affec3..4ef19ce 100644
--- a/owlps-positioning/src/multilaterationalgorithm.cc
+++ b/owlps-positioning/src/multilaterationalgorithm.cc
@@ -1,5 +1,6 @@
 #include "multilaterationalgorithm.hh"
 #include "minmax.hh"
+#include "mobile.hh"
 
 using namespace std ;
 using std::tr1::unordered_map ;
@@ -30,6 +31,26 @@ MultilaterationAlgorithm::~MultilaterationAlgorithm()
 /* *** Operations *** */
 
 
+double MultilaterationAlgorithm::
+make_constant_term(const Measurement &measurement)
+{
+  assert(request) ;
+  assert(request->get_mobile()) ;
+  const AccessPoint *ap = measurement.get_ap() ;
+  assert(ap) ;
+
+  return
+    ap->get_trx_power() +
+    ap->get_antenna_gain() +
+    20 * log10(
+      300000000.0 /
+      ap->get_frequency() /
+      (4 * M_PI)
+    ) +
+    request->get_mobile()->get_antenna_gain() ;
+}
+
+
 Result MultilaterationAlgorithm::compute(const Request &_request)
 {
   request = &_request ;
diff --git a/owlps-positioning/src/multilaterationalgorithm.hh b/owlps-positioning/src/multilaterationalgorithm.hh
index 6c18084..905278e 100644
--- a/owlps-positioning/src/multilaterationalgorithm.hh
+++ b/owlps-positioning/src/multilaterationalgorithm.hh
@@ -15,6 +15,7 @@ protected:
 
   /** @name Operations */
   //@{
+  double make_constant_term(const Measurement &measurement) ;
   void compute_ap_distance_circles() ;
   Point3D multilaterate() ;
   //@}