An RFID (radio frequency identification) reader comprising: a location or movement determination component configured to measure location or acceleration of the reader in three dimensions; at least one RFID radio having a first antenna; at least one data memory component; at least one input/output component configured to prompt a user to move the reader; and at least one processor coupled among the location or movement determination component, the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to: transmit a first RF (radio frequency) query using the RFID radio; characterised in that the processor is further configured to calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna; calculate a trajectory or positions of the moving reader using data from the location or movement determination component; and determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag. a location or movement determination component configured to measure location or acceleration of the reader in three dimensions; at least one RFID radio having a first antenna; at least one data memory component; at least one input/output component configured to prompt a user to move the reader; and at least one processor coupled among the location or movement determination component, the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to: transmit a first RF (radio frequency) query using the RFID radio; characterised in that the processor is further configured to calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna; calculate a trajectory or positions of the moving reader using data from the location or movement determination component; and determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag. transmit a first RF (radio frequency) query using the RFID radio; characterised in that the processor is further configured to calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna; calculate a trajectory or positions of the moving reader using data from the location or movement determination component; and determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag.