A data reading system (10, 100) for tracking positions of a plurality of tagged items (46,146), comprising: an RFID data reader (50, 150) having a read region (13, 113); a conveyor of a conveyor system (30, 32) configured to transport items (46, 146) through the read region (13, 113) of the RFID data reader (50, 150); a processor in operative communication with the RFID data reader (50, 150); wherein the RFID data reader (50, 150) is for each item (46, 146) configured to: (a) obtain data from an RFID item tag (52, 152) being passed through the read region (13, 113); (b) obtain a first reading of the RFID item tag (52, 152) at a first time; (c) obtain a second reading of the RFID item tag (52, 152) at a second time; and the processor is configured to estimate an initial position of each RFID item tag (52, 152) based at least on the first and second readings, and to determine a sequential order at which each item (46, 146) of the plurality of tagged items reaches a reference position on the conveyor of the conveyor system (30, 32), said reference position being assumed later in time than the initial position; characterized in that the RFID item tag (52, 152) further includes a tag antenna configured to transmit an identifier code, and wherein the RFID data reader (50, 150) includes an antenna positioned over the conveyor of the conveyor system (30, 32) at a suitable height (H ant) depending on the expected size of the items (46, 146) being processed, and configured to receive the identifier code from the tag antenna; and the processor is further configured to assign the respective identifier code to each item (46, 146) carrying the respective RFID item tag (52, 152) based on the determined order at which the item (46, 146) reaches the reference position, wherein the processor is configured to calculate the time at which the respective items reaches the reference position by the following formula: T k ref2 = T S0 + x _ ref 2 − x _ est /v i; wherein T k is the time at which the respective item reaches the reference position; T S0 is the timestamp associated to the first reading; x_est is the estimated initial position of the respective item (46, 146) at the timestamp T S0 associated to the first reading; x_ref 2 is the reference position; and v i is the speed of the conveyor. an RFID data reader (50, 150) having a read region (13, 113); a conveyor of a conveyor system (30, 32) configured to transport items (46, 146) through the read region (13, 113) of the RFID data reader (50, 150); a processor in operative communication with the RFID data reader (50, 150); wherein the RFID data reader (50, 150) is for each item (46, 146) configured to: (a) obtain data from an RFID item tag (52, 152) being passed through the read region (13, 113); (b) obtain a first reading of the RFID item tag (52, 152) at a first time; (c) obtain a second reading of the RFID item tag (52, 152) at a second time; and the processor is configured to estimate an initial position of each RFID item tag (52, 152) based at least on the first and second readings, and to determine a sequential order at which each item (46, 146) of the plurality of tagged items reaches a reference position on the conveyor of the conveyor system (30, 32), said reference position being assumed later in time than the initial position; characterized in that the RFID item tag (52, 152) further includes a tag antenna configured to transmit an identifier code, and wherein the RFID data reader (50, 150) includes an antenna positioned over the conveyor of the conveyor system (30, 32) at a suitable height (H ant) depending on the expected size of the items (46, 146) being processed, and configured to receive the identifier code from the tag antenna; and the processor is further configured to assign the respective identifier code to each item (46, 146) carrying the respective RFID item tag (52, 152) based on the determined order at which the item (46, 146) reaches the reference position, wherein the processor is configured to calculate the time at which the respective items reaches the reference position by the following formula: T k ref2 = T S0 + x _ ref 2 − x _ est /v i; wherein T k is the time at which the respective item reaches the reference position; T S0 is the timestamp associated to the first reading; x_est is the estimated initial position of the respective item (46, 146) at the timestamp T S0 associated to the first reading; x_ref 2 is the reference position; and v i is the speed of the conveyor. T k is the time at which the respective item reaches the reference position; T S0 is the timestamp associated to the first reading; x_est is the estimated initial position of the respective item (46, 146) at the timestamp T S0 associated to the first reading; x_ref 2 is the reference position; and v i is the speed of the conveyor.