Patent ID: 8149160

Claim:
A method for determining distance traveled by a vehicle over railroad tracks, the railroad tracks comprising two rails and a plurality of tie plates connecting the rails to a plurality of cross ties, the method comprising: mounting a pair of microwave transceivers to the vehicle a fixed distance apart so that both microwave transceivers lie along a line parallel to the rails and bisecting a portion of the rail tie plate that extends inward past the rail, wherein one microwave transceiver is located closer to the front of the vehicle and one closer to the rear of the vehicle and wherein the microwave transceivers are directed toward to the rail tie plates so that signals transmitted from the microwave transceivers will be reflected back to the same transceiver; collecting energy reflected from an identifiable feature in the rail bed as the vehicle moves to determine when each transceiver passes over the identifiable feature; determining the time delay between the forward transceiver passing over a feature and the rearward transceiver passing over the same feature; from the time delay and the fixed distance between the transceivers, calculating the velocity of the vehicle as the vehicle moves over the identifiable feature; repeating this calculation over a given distance for a plurality of identifiable features; plotting a velocity versus time curve over the given distance; and integrating the curve to determine total distance traveled.