Importance

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Abstract

A GPS receiver includes a power supplying status detector for deriving a power-on or power-off signal by detecting a power supplying status of the GPS receiver, a clock for measuring time, a memory controller for controlling a nonvolatile memory upon receiving the power-off signal to store a time measured by the clock when the power is turned off or a time when the last ephemeris data is obtained and the last ephemeris data, and a position calculating circuitry for calculating the position of the user station upon receiving the power-on signal. A time duration is calculated from the time measured by the clock and the time stored in the nonvolatile memory. If it is determined that the measured time duration is shorter than a predetermined period of time, the positioning is performed based on the respective ephemeris data stored in the nonvolatile memory, whereas if it is determined that the measured time duration is no less than the predetermined period of time, the positioning is performed based on ephemeris data newly collected from the respective GPS satellites.

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First Claim