| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and a device for obtaining availability as an index indicating the probability that a service complying with a demand of a navigation system defined by ICAO can be provided, i.e., the operation rate of a system. SOLUTION: Momentary availability Ai (R, ti), represented as the probability that the request of the navigation system at an observation position at time ti be found from the possibility that (i) satellites going out of order at sampling time ti of uneven intervals obtained by finding the rising and setting timesγi of all GPS satellites on one sidereal day at a prescribed mask angle at a certain observation position and merging the rising and setting timesγi with sampling time of equal intervalsΔh, the number complying with the current request of the navigation system, and the total number of combinations wherein (i) satellites goes out of order. Consequently, the sampling number can be decreased, so that the arithmetic time can be shortened greatly.
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