The only systems currently available that can locate tags in three dimensions are RFID systems that use phased array antennas. These systems focus an RFID reader antenna in a narrow beam that is swept across the read zone. With two such interrogators covering the same area, a system can locate a tag in 3D within one foot or so.
There has also been some work conducted on handhelds that shine a laser on a tagged object when one looks for that specific object. This could be helpful in a large warehouse where there are many boxes if one needs to locate a single box. To my knowledge, however, no system using this technology is yet on the market.
—Mark Roberti, Editor, RFID Journal
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