An interrogator system to determine the relative positions of a plurality of passive wireless transponders, the interrogator system comprising: a transceiver to provide an interrogation carrier wave; and a processor communicably coupled to the transceiver, characterized in that the interrogator system further comprises: a processor-readable nontransitory storage medium including machine executable instructions that when executed by the processor, cause the processor to: receive information from each of a plurality of passive wireless transponders that each comprises at least one unique identifier and each identifies at least one neighboring passive wireless transponder that is spatially proximate the respective passive wireless transponder from which the information is received, wherein at least one said neighboring passive wireless transponder identifies another of the plurality of passive wireless transponders which is spatially proximate to the at least one said neighboring passive wireless transponder; and determine a relative position of each of the passive wireless transponders with respect to one another based at least in part on the information received from each passive wireless transponders. a transceiver to provide an interrogation carrier wave; and a processor communicably coupled to the transceiver, characterized in that the interrogator system further comprises: a processor-readable nontransitory storage medium including machine executable instructions that when executed by the processor, cause the processor to: receive information from each of a plurality of passive wireless transponders that each comprises at least one unique identifier and each identifies at least one neighboring passive wireless transponder that is spatially proximate the respective passive wireless transponder from which the information is received, wherein at least one said neighboring passive wireless transponder identifies another of the plurality of passive wireless transponders which is spatially proximate to the at least one said neighboring passive wireless transponder; and determine a relative position of each of the passive wireless transponders with respect to one another based at least in part on the information received from each passive wireless transponders. a processor-readable nontransitory storage medium including machine executable instructions that when executed by the processor, cause the processor to: receive information from each of a plurality of passive wireless transponders that each comprises at least one unique identifier and each identifies at least one neighboring passive wireless transponder that is spatially proximate the respective passive wireless transponder from which the information is received, wherein at least one said neighboring passive wireless transponder identifies another of the plurality of passive wireless transponders which is spatially proximate to the at least one said neighboring passive wireless transponder; and determine a relative position of each of the passive wireless transponders with respect to one another based at least in part on the information received from each passive wireless transponders. receive information from each of a plurality of passive wireless transponders that each comprises at least one unique identifier and each identifies at least one neighboring passive wireless transponder that is spatially proximate the respective passive wireless transponder from which the information is received, wherein at least one said neighboring passive wireless transponder identifies another of the plurality of passive wireless transponders which is spatially proximate to the at least one said neighboring passive wireless transponder; and determine a relative position of each of the passive wireless transponders with respect to one another based at least in part on the information received from each passive wireless transponders.