Calibration Procedure
If the compass has been calibrated or set to variance zone
number incorrectly, or you are driving in specific places (tunnel,
parking lot in building, underground parking ...
Limitations Of The Navigation system
GPS Signal Reception State
As the GPS satellite frequency is received/transmitted in
straight lines, reception may not work if hiding devices are placed on
or near the GPS antenna or when traveling through the following
locations.
•
Tunnels
...