A method includes constructing a WTG structure including a first wall and a second wall, the first and second walls defining a walk though pass way between an entrance and an exit, positioning at least one sensor at the entrance and the exit of a cavity defined by the walk though pass way, positioning at least one first antenna facing toward an inside region of the WTG structure, positioning at least one second antenna facing away from the inside region of the WTG structure, connecting an RFID reader to the at least one first and second antennas, and, judging, via a judgement module, if an RFID tag is located inside or outside the walk though gate structure.