@@ -54,7 +54,7 @@ The position of the satellites is calculated on the ground and is made public by
This phenomenon is problematic because it is difficult to model and eliminate. Any reflective object placed in the vicinity of the GPS station's antenna can reflect part of the signal from the satellite back to the antenna. **The signal will therefore be deteriorated,** more difficult to interpret and therefore a source of large errors. Moreover, this kind of phenomenon is very frequent in the life of any user, especially in the city where the path that the signal makes is rarely clear.
[The clock synchronization problem - A REFAIRE](The%20clock%20synchronization%20problem)
The satellites of the GNSS system are equipped with **several atomic clocks**; however, **their high accuracy has a limit.** The corrections for the offset of the clocks are transmitted in the "navigation message". These corrections are calculated by reference ground stations and are used to compensate for the continuous deviation of the clocks. The uncertainty in the receiver clock, which is much less accurate since it is not an atomic clock, is considered an additional unknown, hence the need for at least four satellites.
