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Accurate vehicle positioning with respect to a geographical database is fundamental to successful use of in-vehicle navigation systems. In this paper, the authors examine known distortions in the database by their effect on vehicle positioning as measured by the Certainty Factor. The results are shown graphically as a function of distance as the vehicle traverses the distorted region of the database. Three cases are examined using two vehicle positioning algorithms - one more heavily weighted with GPS than the other. A conclusion made is that the Certainty Factor concept is a valid measure for examining database distortions as well as vehicle positioning algorithms.

The five year development of NAVMATE from 1989 through its deployment as GUIDESTAR in the 1995 Oldsmobile 88 is discussed within the context of three development phases of hardware and software. In Phase I, fundamental issues of the turn-by-turn route guidance concept and the factors affecting vehicle positioning were assessed. In Phase II, prototype hardware that utilized the CRT display and touch screen of the 1992 Trofeo were built to test customer response. The aftermarket installation design of Phase III (current design) focussed on a simplified man-machine interface, ease of system installation and removal and robust performance. This design provided the basis for the Oldsmobile GUIDESTAR System.