Self-Inertial Navigation Limitations

Limitations of the self-inertial portion of navigation system can cause some discrepancies between actual position and indicated vehicle position. If a large discrepancy exists, and system is receiving GPS signals, system will adjust indicated vehicle position to GPS position. If GPS signals are not available, vehicle position must be tuned manually. Positioning errors may be caused by the following:

• Moving vehicle with engine stopped (tow truck or ferry), or if vehicle is spun on a turn table.
• Tire slippage, continuous tire slippage on a slippery surface, or driving with snow chains.
• Changes in tire rolling diameters, abnormal tire pressures, or different diameter tires.
• Frequent lane changes across a wide highway or continuous driving on a straight or gently curving highway.
• Tolerances in system and map accuracy, driving on roads not on the map, driving on a road that winds in one direction (loop bridge, an interchange, or spiral parking garage).
• Driving on a road with a series of sharp hair-pin turns.
• Driving on one of 2 close parallel roads.
• After making many 90 degree turns.