| 摘要 |
PROBLEM TO BE SOLVED: To recognize an area where a communication error is easily caused and to reduce a blind zone by comparing a receivable area which is calculated after reception of a GPS signal with a stored receivable area and notifying the communication obstacle data which are obtained by deciding the change of a peripheral communication environment based on the result of the above comparison. SOLUTION: A GPS receiving part 12 supplies the data to an area calculation means 13 to detect an obstacle, etc., out of the GPS signals received via a GPS antenna 11. The means 13 calculates a receivable area from the GPS signals received from a GPS satellite. An area storage means 14 successively stores the receivable areas which area calculated by the means 13. An area comparison means 15 compares the latest receivable area calculated by the means 13 with that stored in the means 14. A fault decision means 16 decides the presence or absence of a communication fault based on the comparison result of the means 15, decides the change of a peripheral communication environment and outputs the decision result to a notification means 17. |
