Abstract: A mobile controller unit has a radio positioning system and a two-way communication system and a rover unit also has a radio positioning system and a two-way radio communication system. The controller unit can query the rover unit to send its location data so that the rover unit can be located and if desired, found, such as in the case of a lost child or items. Relative position between the controller and the rover can be displayed on the controller along with an arrow showing where the rover is, as well as how fast it is moving, a track of its movement and other data. The system can also operate in conjunction with a network system that has a PDE and an application server that perform some of the communications and calculation functions.

Abstract: A mobile controller unit has a radio positioning system and a two-way communication system and a rover unit also has a radio positioning system and a two-way radio communication system. The controller unit can query the rover unit to send its location data so that the rover unit can be located and if desired, found, such as in the case of a lost child or items. Relative position between the controller and the rover can be displayed on the controller along with an arrow showing where the rover is, as well as how fast it is moving, a track of its movement and other data.

Abstract: A traffic signal preemption system, and a related method for its use, using differential global positioning system (GPS) measurements for accurate monitoring of the position, speed and direction of an emergency or service vehicle approaching a controlled intersection. The preemption system includes a reference GPS receiver, for computing GPS measurement corrections, and a GPS receiver in each vehicle, which transmits its GPS measurements by radio to a receiver located at the controlled intersection. A computer also located at the intersection uses corrected vehicle position, speed and direction measurements, in conjunction with previously recorded data defining approach routes to the intersection, to determine the optimum time to switch a traffic light controller to preemption mode to permit safe passage of the vehicle. GPS measurement corrections may be applied in a vehicle computer or in the computer located at the intersection.