A method of eliminating user position biases caused by satellite constellation changes or differential signal gain/loss is provided. The method comprises: (A) substantially continuously determining an unbiased user's position by using a radio receiver”; (B) detecting a “detectable event” by using the radio receiver; (C) measuring a bias caused by the detectable event; (D) performing an update process by accumulating each bias caused by at least one detectable event to generate an accumulated bias; and (E) eliminating the accumulated bias at each Epoch by using a correction process.