Patent ID: 6072421
Filing Date: 2000-06-06
Classification: G01S,G08G

Abstract:
In a roadway system having transponders spaced along the roadway outside the intended track for traveling vehicles, each transponder transmitting a reply signal in response to a vehicle originated interrogation signal, a method of determining a vehicle's position along the roadway, comprising:(a) transmitting the vehicle originated interrogation signal at an unknown angle at least partially transverse to the vehicle's direction of travel towards the transponders;(b) receiving the reply signal in response to the vehicle originated interrogation signal, said reply signal identifying the position of the transponder;(c) measuring a time difference between transmission of the vehicle originated interrogation signal and receipt of each corresponding reply signal;(d) determining a distance between the vehicle and at least one of the responding transponders from the measured time differences; and(e) determining the position of the vehicle along the roadway using a selected triangulation method based on the distance between the vehicle and at least one responding transponder and on the position of the transponder as identified by its reply signal.