Using a mesh of radio frequency identification tags for tracking entities at a site

A method for tracking entities, to determine at least a relative location of the entities at a site, comprising the steps of:

• (a) creating a mesh network at the site that is formed of a plurality of portable radio frequency identification (RFID) tags, and a plurality of fixed RFID tags, all of which transmit and receive radio signals, the portable RFID tags each being associated with a different entity from a plurality of different types of entities that can move around at the site, each portable RFID tag being physically coupled or attached to the entity with which it is associated, wherein a portable RFID tag that has not moved from a previous known location comprises a static RFID tag;
• (b) repetitively causing each RFID tag to transmit a signal that conveys an identification of the RFID tag that is transmitting the signal, the signal that is transmitted being received by any other RFID tag disposed within a receiving range of the signal that was transmitted, wherein the RFID tags that are receiving the signal include one or more of the fixed RFID tags or static RFID tags, each fixed or static RFID tag having a known position on the site;
• (c) each RFID tag that receives the signal being transmitted determining a location indicative parameter and saving the location indicative parameter in connection with the identification of the RFID tag that transmitted the signal;
• (d) forwarding data comprising the location indicative parameter and identification of the RFID tag for each of the signals that was received by an RFID tag, to a processor, along with an identification of the RFID tag that is forwarding the data;
• and
• (e) using collaborative multi-lateration for processing location indicative parameters in relation to the known positions of the fixed or static RFID tags and the identification of the RFID tags forwarding the data, as well as the identification of the portable and fixed or static RFID tags originally transmitting signals, for determining at least relative positions of the entities at the site.