Patent ID: 7746275

Claim:
A position detecting system, comprising: an RFID terminal configured to transmit an identification information signal by radio; a plurality of receiving devices configured to receive the identification information signal; and a position detecting server configured to receive a reception notification of the identification information signal from each of the receiving devices; wherein the RFID terminal includes a part configured to perform radio transmission of a plurality of identification information signals having different radio strengths, at designated time intervals; the receiving devices are configured to report, when receiving each identification information signal, the reception notification of the received identification information signal to the position detecting server; and the position detecting server includes a part configured to calculate the center of gravity of positions of receiving devices reporting the reception notifications, of each time interval, configured to determine that the RFID terminal has performed the radio transmission of a predetermined one of the identification information signals at a current time interval, depending on the number of receiving devices reporting the reception notifications of the predetermined identification information signal, and configured to estimate a position of the RFID terminal based on a calculation result of the center of gravity of the current time interval where a weighting factor is applied and a calculation result of the center of gravity of a previous time interval.