Abstract: A GPS surveying system uses at least four GPS satellites which travel on satellite orbits and a GPS surveying system having a first receiving apparatus for receiving radio waves to be transmitted from each of the GPS satellites and a second receiving apparatus for receiving radio waves to be transmitted from each of the GPS satellites. The first receiving apparatus is disposed in a known point and the second receiving apparatus is disposed in an unknown point. An integrated carrier phase of the radio waves to be received by each of the receiving apparatuses is measured. The integrated carrier phase is recorded at every predetermined interval of time. Three-dimensional coordinate values of the unknown point are obtained based on the recorded integrated carrier phase. When interruption of receiving of the radio waves to be transmitted from the GPS satellites has occurred during the measuring and the recording step, the interruption of receiving is detected.