Patent ID: 8912953

Claim:
A GPS receiver, comprising: a navigation signal receiving unit receiving a plurality of navigation signals from a plurality of respective satellites, including a first navigation signal from a first satellite, and wherein a first communication path from the first satellite to the receiving unit is unobstructed; a navigation signal processing unit acquiring position information of each respective satellite from the received navigation signals and measuring respective pseudo-ranges from the respective satellites to the receiving unit, including a first pseudo-range of the first satellite; and a pseudo-range estimating unit determining an abnormal state of a second navigation signal from the first satellite to the receiving unit, wherein the second navigation signal is transmitted a time after the first navigation signal was transmitted and, upon determining the abnormal state, estimating a current location of the receiving unit and calculating a current position of the first satellite based upon first satellite position information previously stored in a memory before the abnormal state was determined, and estimating a second pseudo-range of the first satellite based upon the calculated current position of the first satellite and the estimated current location of the receiving unit, wherein the abnormal state of the second navigation signal is determined based on a change according to time of a pseudo-range or a cater phase which is a measured value acquired from a navigation signal.