Positioning Toronto's Transit vehicles: Integrating low-cost GPS, odometers, gyros and signposts

Until recently the positioning of transit vehicles was carried out using traditional technologies such as odometer/gyro sensors and signposts. The Toronto Transit System is no exception. Unfortunately, both the odometer and the gyro drift over time, causing significant error in the given position. Signposts, on the other hand, suffer from limitations such as incapability to ascertain the exact location of a vehicle between two signposts. To overcome these limitations, integrated positioning systems are under development consisting of a low-cost autonomous GPS system and one or more of the conventional systems mentioned above. The authors present the new systems, along with results of field trials.