Self-Inertial Navigation Limitations

The limitations of the self-inertial portion of the navigation system (the yaw rate sensor and the vehicle speed signal) can cause some discrepancies between the vehicle's actual position, and the indicated vehicle position (GPS vehicle position). However, if GPS signals cannot be received, you must tune the vehicle's position manually.

The following circumstances may cause vehicle positioning errors:

• Moving the vehicle with the engine stopped, such as by ferry or tow truck, or if the vehicle is spun on a turntable
• Tire slippage, changes in tire rolling diameters, and some driving situations may cause discrepancies in travel distances. Examples of this include:
  • Continuous tire slippage on a slippery surface
  • Driving with snow chains mounted
  • Abnormal tire pressure
  • Incorrect tire size
  • Frequent lane changes across a wide highway
  • Continuous driving on a straight or gently curving highway
  • Very bumpy roads
• Tolerances in the system and map inaccuracies sometimes limit how precisely the vehicle position is indicated. Examples of this include:
  • Driving on roads not shown on the map (map matching is not possible).
  • Driving on a road that winds in one direction, such as a loop bridge, an interchange, or a spiral parking garage.
  • Driving on a road with a series of sharp hair-pin turns.
  • Driving near a gradual highway exit or transition.
  • Driving on one of two close parallel roads.
  • Making many 90 degree turns.
  • The direction to destination icon or the "Destination icon" shown or the map may be up to several hundred feet away from the actual location.
• The system does not know the number of lanes of a highway, therefore it may place the vehicle icon several feet behind an intersection.