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.

Abstract: A tripod lock device for locking a tripod having three identical legs each composed of a fixed leg and a movable leg slidably disposed between a pair of parallel spaced leg members of the fixed leg for adjusting the length of the leg in a telescopic manner. The tripod lock device is composed of three identical leg lock units each associated with one of the three legs of the tripod. Each of the leg lock units includes a frame, an eccentric cam and an engagement portion. The frame has a through-hole in which the leg members of the fixed leg and the movable leg are disposed, with one of the leg members secured to the frame. The engagement portion comprises a rod disposed on the frame at a position adjacent to said one leg member. The eccentric cam includes a presser portion and a hook.