1. A portable encoded information reading (EIR) terminal comprising: a microprocessor; a memory; an RFID reading device; a display; wherein said portable EIR terminal is configured, responsive to successfully reading a plurality of RFID tags attached to a plurality of items sustained by a physical structure, to group said plurality of read RFID tags into zero or more clusters, by correlating quantities of RFID tags read within several time periods to spatial positions of coverage shapes of RF signals transmitted by said RFID reading device during said several time periods, said spatial positions of said coverage shapes of said RFID signals determined based on spatial positions and orientations of said portable EIR terminal during said several time periods; wherein said portable EIR terminal is further configured to display a quantity of RFID tags within each cluster overlaid over an image of said physical structure, with a visual reference to a fragment of said physical structure corresponding to spatial positions of one or more RFID tags comprised by each cluster.