Automatic vehicle location Dallas test results

The FCC allocation of a wide band channel at 900 MHz for an Automatic Vehicle Monitoring (AVM) service presented the opportunity to Hazeltine to develop a vehicle locating system that can support 5,000 vehicles with high location accuracy information and rapid two-way data message transmissions. The system is configured to have variable up-date rate of information dependent on user requirements while providing a moving vehicle location accuracy of 300 feet (95% confidence). The basic system utilizes pulse trilateration with an automatic computer inverse hyperbolic location solution-The vehicles are polled sequentially and reply to multiple fixed receivers. Time difference of arrival data is collected and processed automatically. The solution of the intersection of hyperbolic lines via a Newton-Raphson iteration method is utilized in the computer location process. The receiver sites are configured in a triangular cell pattern lending the system to graceful growth capability. Test results obtained in the Phase I program performed for the City of Dallas have demonstrated the accuracy and general feasibility of the location technique in the Dallas Police Departments Southwest Patrol District. A single interrogation locating performance of 270 feet for 95% of the locations and 60 feet for 50% of the locations has been documented. Better than 90% of the randomly distributed vehicle positions were successfully located within the accuracy distribution limits. Moving vehicle plots showing the reported vehicle positions in relation to the traversed roads gives a pictorial presentation of the frequency of error vs. magnitude of error of the histogram plots.