Apparatus for passively measuring the velocity of a ferrous vehicle along a path of travel

摘要

A passive velocity measuring system which includes first and second biaxial fluxgate magnetometers separated by a known distance and oriented precisely with respect to one another and with respect to the path of travel of a ferrous vehicle whose velocity is to be determined. An indication of the velocity of the vehicle is obtained from the ratio of the time derivative of the magnitude of the vehicle's magnetic induction to the negative of the spatial derivative of this same quantity.