| 摘要 |
A GPS receiver calculates a position with as high accuracy as possible by appropriately setting a threshold of a reception level of the signal from each GPS satellite and a DOP threshold based on an interrelation between the satellites. A positioning calculator performs predetermined positioning calculation using a reception signal from each satellite. When the reception level of the satellites are below a threshold set by a reception-level-threshold setting section, and thus a positioning-calculation determination section determines that the positioning cannot be performed, a threshold change processor gradually relaxes the threshold. Once relaxing the threshold enables the positioning calculation, a DOP value is determined from a constellation of the satellites used for the positioning calculation, and then is compared with a DOP threshold set by a DOP threshold setting section. If a DOP value determination section determines that the DOP threshold is not satisfied, the DOP threshold is relaxed.
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