diff --git a/matlab/GPSaidedINS.m b/matlab/GPSaidedINS.m
index db8a4ce3fbac71a1595be0c5b9f172f0a3ee5d71..863cbd6951605e7e198b1195a463c9734b44ba04 100644
--- a/matlab/GPSaidedINS.m
+++ b/matlab/GPSaidedINS.m
@@ -81,7 +81,7 @@ for k=2:N
     sv=5;
     %control action
     a=[a,sum(sqrt(out_data.diag_P(1:3,k-1)))];
-    if sum(sqrt(out_data.diag_P(1:3,k-1)))<15.0
+    if sum(sqrt(out_data.diag_P(1:3,k-1)))<20.0
         turn=false;
     else
         turn=true;
diff --git a/paper/main.bib b/paper/main.bib
index 47eeba225510151c1184e4713d23f6fed1b29624..44b7b49940eee168813736ee7471ddd9d2cbf435 100644
--- a/paper/main.bib
+++ b/paper/main.bib
@@ -292,7 +292,7 @@ month={Sept},}
 }
 
 %libro su GPS+inertial navigation
-@book{Grewal:2007:GPS:1237963,
+@book{bib:gps-imu,
  author = {Grewal, Mohinder S. and Weill, Lawrence R. and Andrews, Angus P.},
  title = {Global Positioning Systems, Inertial Navigation, and Integration},
  year = {2007},
diff --git a/paper/sections/04-fusion.tex b/paper/sections/04-fusion.tex
index bac54a4eba45efaf70ee0c77bfe6113325bb1e36..acc5d7a4fb841c30a5462ba5804e0919c71e1c30 100644
--- a/paper/sections/04-fusion.tex
+++ b/paper/sections/04-fusion.tex
@@ -5,3 +5,9 @@
 \item Spiega come lo fai (equazioni). rifrasa dal tast del corso AS1
 \end{itemize}
 
+
+It is now discussed an implementation of the presented model. We will use to discuss some of the different types of analysis that can be done with this abstarction an implementation of GPS-IMU sensor fusion. Sensor fusion is the technique of merging the measurements that come from different sensors. If well made, it enhances the advantages of the different sensors while compensating for the disadvantages.
+
+Inertial measurement units (IMUs) are sensors that measure accelerations and angular velocities of the device. Such sensors are usually carachterized by relatively low power consumption \todo{find reference}, providing relative measurements and continuous availability.
+
+