Liberty - Built-in Sat Nav

Hi,
I am wondering if the sat-nav system in the liberty range has a inertial system with it i.e if you go into the cross city tunnel will it lose the plot or will it continue on without any issues. As I have seen where in the city i.e tall buildings, a sat-nav is useless as it keeps losing the plot.
any help on this will be most appreciated
grunta007
I am wondering if the sat-nav system in the liberty range has a inertial system with it i.e if you go into the cross city tunnel will it lose the plot or will it continue on without any issues. As I have seen where in the city i.e tall buildings, a sat-nav is useless as it keeps losing the plot.
any help on this will be most appreciated
grunta007