Real-time vehicle location with desired accuracy

Magnetic markers are provided on automated highway system for lateral control of vehicles within a lane. We propose a pseudo-noise (PN) code to be carried by the magnetic markers. The PN code will be used by vehicles for range measurement. Every vehicle is provided with the code layout on the road with respect to the physical location of every binary magnetic signal. A vehicle has a replica of the signal and measures the phase of the received signal with respect to the replica and infers its position on the road. The positioning accuracy is subject to design and depends on the magnetic markers layout on the road. The probability of error with short range magnetic signals is negligible compared with radio navigation systems. Unlike radio signals, magnetic codes do not interfere, and multipath is not an issue. However, errors do exist and an attractive feature of the method is its error detection capability. Errors can be detected and corrected shortly after they occur and the error detection and correction delays are subject to design. Error bounds can also be specified with respect to the signal code design.