Patent ID: 7170820

Claim:
An object tracking system comprising: four or more sensors at different sites, each sensor being capable of detecting a signal from an object; a control device for repeatedly, in response to the outputs of the sensors, selecting a sub-set of the sensors and determining the amount by which the times at which the sensors of the sub-set receive the signal are delayed with respect to each other to enable calculation of the current location of the object; a processing device for processing an output from a first sensor of said sub-set in accordance with a signal representing the time at which predetermined events occur within an output from a second sensor of said sub-set, in order to determine the delay between the receipt of the signal by the first and second sensors; and a device for forming a combination of segments of said output of said first sensor, the segments being staggered with respect to each other by intervals corresponding to the delays between the events in the output of the second sensor, and a determination device for determining said time delay from the position of a feature within said combination.