RFID location systems and methods

Systems and methods for locating radiofrequency identification (RFID) tags are described. In one embodiment, radiofrequency (RF) signals are transmitted from one or more RFID readers, and in accordance therewith, backscattered signals are received from a tag to be located. A plurality of measured position parameters are used to determine a location of the tag. In one embodiment, one reader may transmit and three readers may receive signals to determine the position of a tag. In other embodiments, multiple readers may transmit and receive. In another embodiment, one reader may transmit from different positions to locate a tag. Embodiments of the invention may be used to track a moving tag. A reader's position may be determined using GPS, reference tags, or the reader may be positioned in a known location. A map may be provided to a user to display the location or movement of a tag or a corresponding item.