Importance

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Abstract

An automatic vehicle location system obviates the need for frequent, scheduled position and movement change messages from field vehicles by having each field vehicle send position and movement update messages only when a change occurs in a monitored vehicle characteristic, and only when that change is accompanied by traversing a decision point on a stored electronic map. Sensors for monitoring such characteristics include, turn signal indicators, brake indicators, back-up indicators, speedometers, compasses and accelerometers. Upon reaching a decision point, and upon one of the signals from a sensor reaching a threshold, the Automatic Vehicle Location (AVL) box in the mobile unit of the field vehicle causes the Mobile Data Terminal (MDT) to transmit a position update message to a Dispatch Center. The Dispatch Center and the MDT contain identical maps, and extrapolate the vehicle's position between decision points according to identical algorithms.

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First Claim