Etak, Inc.

Darrell L Mathis

Richard Frederick Poppen

Kenneth Alan Milnes

A system for tracking an object (for example tracking an automobile as it moves over streets) using an electronic map and a GPS receiver. The GPS receiver accepts data from a number of satellites and determines a GPS derived position and velocity. Based on the previous position of the object, the GPS derived position, the velocity, the DOP and the continuity of satellites for which data is received, the system determines whether the GPS data is reliable. If the GPS data is reliable, the previous position of the object is updated to the GPS derived position. The updated position is then matched to a map of roads.

Navigation system using GPS data

A navigation system comprising a relative positioning system (RPS) with dead reckoning and map matching and an absolute positioning system (APS) is provided and operated in such a manner that APS position information is used for updating RPS position and contour of equal probability (CEP) information as required. The APS may comprise a Loran-C or a global positioning system (GPS). Different criteria are used for resetting the RPS depending on whether or not the navigation system comprises a Loran-C or a GPS due to the different levels of precision of the Loran-C and the GPS. When the RPS is reset or updated, it is updated to the current APS position with its offset, if any. Its contour of equal probability (CEP) may also be adjusted.

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San Francisco, CA, United States of America

Darrell L Mathis