| 摘要 |
PURPOSE:To enable a satellite to be quickly re-captured when a state is returned to a receivable state again by switching a reception mode so that only the satellite at a position with the maximum angle of elevation predicated at a time when the reception of a satellite wave is disabled can be captured. CONSTITUTION:When a vehicle progresses to a tunnel, etc., and a state where no satellite can be captured is continued for a prescribed time, the capturing operations of the satellites S1-S4 are interrupted. Simultaneously, it is calculated which satellite is the one at the position with the maximum angle of elevation predicted at that time. Assuming that the satellite at the position with the maximum angle of elevation is the satellite S3, a GPS receiver switches the reception mode so as to capture only the satellite S3 at the position with the maximum angle of elevation, and performs the capturing operation of only the satellite S3. When the satellite S3 at the position with the maximum angle of elevation is captured, a re-captured satellite S3 and another three satellites obtained from the almanac information of the satellite S3 and most suitable for a three-dimensional measuring position at that time are selected, and the ordinary sequential multiplex reception of those four satellites are started, and when the capture of the satellite is disabled, the satellite at the position with high angle of elevation is re-calculated, and after that, the re-capture is repeated. |
