| 摘要 |
<p>Available-satellite data (302) indicating satellites available for satellite positioning is obtained from a GPS receiver (5), and satellites continuously available for satellite positioning this time and the previous n times are extracted as candidate satellites referring to available-satellite record data (303). Four of the candidate satellites are selected so that the satellites used for satellite positioning the previous time are selected with priority as the satellites to be used for satellite positioning this time, and the selected satellites are set in designated-satellite data (304). The GPS receiver (5) performs three-dimensional positioning using the four satellites designated by the designated-satellite data (304). If the number of extracted candidate satellites is three, these three extracted candidate satellites are selected as the designated satellites and are set in the designated-satellite data (304). The GPS receiver (5) performs two-dimensional positioning using these three designated satellites. If the number of extracted candidate satellites is smaller than three, satellite positioning is not performed.</p> |
