Patent ID: 8199055

Claim:
A method of locating an object placed on a surface, the method comprising the steps of: providing a plurality of elements including a plurality of wireless transmitters and a plurality of wireless receivers, in such a configuration as to form a plurality of pairs of a transmitter and a receiver able to detect a signal from the transmitter in the absence of the object, each such pair defining one of a plurality of normally clear lines of sight, at least some of which are at an angle to each other; providing a further object that comprises at least one element of the plurality of pairs of a transmitter and a receiver; activating at least some of the wireless transmitters in the presence of the object; and identifying normally clear lines of sight blocked by the object by evaluating responses of the receivers of at least some of the pairs of a transmitter and a receiver able to detect a signal from the transmitter, wherein identifying normally clear lines of sight blocked by the object further comprises (i) evaluating responses of the receivers of the at least one element of one of the pairs included in said further object, and (ii) partitioning the surface into regions of variable extent by moving said further object across the surface, wherein the further object simplifies determination of a position of the object to be located by cutting out signals crossing a region other than that in which the object to located is present.