The-clock-synchronization-problem.md

 Satellites send a signal and users’ receptor receives it. But in order to read the signal properly, both clocks (the satellites and the receptor’s) must have the same time scale.
 
-# **1st synchronization problem:**
+# **1st synchronization problem: the distance calculation is very sensitive to clock errors**
 
 Indeed, if we calculate the time a signal makes to go from the satellites to the receptor, in an ideal world, we only would have to use the fact that ![f11](http://chart.apis.google.com/chart?cht=tx&chl=d=ct). As time is multiplied by the speed of light, distance is very sensible to time mistake: ![f1](http://chart.apis.google.com/chart?cht=tx&chl=dD=%5Cfrac%7Bdt%7D%7Bt%7D)
 
@@ -10,7 +10,7 @@ And the pseudo-distance between the satellite and the receptor ![f6](http://char
 
 Therefore, the localisation problem has 4 unknown parameters: 3 geometrical parameters x, y and z and time t.
 
-# **2nd synchronization problem:**
+# **2nd synchronization problem: the problem with the frequency**
 
 The same problem affects the measurements made thanks to the Doppler Effect. The clock drift is a phenomenon that describes the precision of a clock through time. This drift depends on the quality of the clock : the drift of an atomic clock will be more predictable and smaller than the drift of a quartz clock.