Abstract: An Automatic Location Identification (ALI) system for cellular telephone networks, along with a pseudo Automatic Number Identification (ANI) typically representing a particular face of a cell tower receiving an emergency call, compares the electromagnetic footprint of the call to stored field strength data to ascertain the coordinates of a small polygon subsuming the location of the caller. Along with connecting the emergency call to the emergency (i.e., “911”) dispatch center, the system also transmits the caller's Directory Number (DN), the cell tower location, and the coordinates of the location polygon. This approach gives the emergency dispatch center a more definite location than prior art approaches which only provide a large triangular area based on a cell tower face as the location region of the caller. It can also serve as a back-up to more sophisticated resource-intensive approaches using signal time differentials and the like.

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.