Abstract: The present invention provides a GPS device for measuring the wave height and current direction and speed, which is capable of accurately measuring the wave height (height of the waves) and current direction and speed (tidal current) in any point on the sea, ocean, lake, or marsh, and to a system using such a device. The GPS receiver 2 of the GPS device 1 for measuring the wave height and current direction and speed processes the GPS signals received with the GPS antenna 3 and measures the three-dimensional position of antenna 3. The three-dimensional position data are recorded by the data recording unit 4 connected to the GPS receiver 2. When the floating body 5 having those devices 2-4 installed thereon floats on the sea or ocean, it moves together with the waves and tidal current in the present location.

Abstract: The present invention provides a GPS device for measuring the wave height and current direction and speed, which is capable of accurately measuring the wave height (height of the waves) and current direction and speed (tidal current) in any point on the sea, ocean, lake, or marsh, and to a system using such a device. The GPS receiver 2 of the GPS device 1 for measuring the wave height and current direction and speed processes the GPS signals received with the GPS antenna 3 and measures the three-dimensional position of antenna 3. The three-dimensional position data are recorded by the data recording unit 4 connected to the GPS receiver 2. When the floating body 5 having those devices 2-4 installed thereon floats on the sea or ocean, it moves together with the waves and tidal current in the present location.

Abstract: The object of this invention is to prevent GPS time monitor errors from effecting the distance-measuring accuracy. To achieve the object, a monitor GPS receiver receives GPS signals from each GPS satellite via a receiving antenna, senses satellite data, and obtains observation data on the basis of user clock pulses synchronized with a reference clock from a reference oscillator. A data processing unit computes a pseudo range error value from the satellite data and observation data obtained at the monitor GPS receiver on the basis of the user clock pulses, and formats these data items to generate transmission data. A transmitter combines PN codes with the transmission data on the basis of the user clock pulses to generate a pseudo GPS signal, modulates a carrier signal synchronized with the reference clock, and power-amplifies the modulated output. A transmitting antenna is directed toward a specific stationary satellite and transmits a pseudo GPS signal to a user GPS receiver via the stationary satellite.

Abstract: A clock test apparatus connected to a GPS receiver mounted in a moving body has a frequency counter which counts clocks output from a clock generator incorporated in the GPS receiver for a predetermined period of time. In this manner, a clock frequency is detected and supplied to a clock error identification section. The clock error identification section calculates a short-term stability from the clock frequency, and further calculates a clock error on the basis of the short-term stability. The clock error data is supplied to a dynamics simulator. The dynamics simulator simulates circuit dynamics of the GPS receiver, and models error in the velocity of the moving body relative to a satellite, which results from the clock error, on the basis of the clock error data, thereby analyzing the performance of the GPS receiver.

Abstract: A star sensor compares predetermined star information stored in a memory and actual star information corresponding to star image signals from an imaging device. A processing device generates an attitude signal corresponding to the attitude of a base with respect to the star when the predetermined and the actual star information substantially coincide. A correcting device corrects the predetermined star information when the predetermined star information and the actual star information are not substantially the same.