| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To reduce an amount of data and make a retrieving speed higher by improving altitude data used for two-dimensional positioning operations. <P>SOLUTION: In a positioning calculation based on a GPS satellite signal, at first a three-dimensional positioning operation is carried out, and if the three-dimensional positioning operation fails, a two-dimensional positioning operation is carried out based on an altitude obtained by retrieving an altitude table. The altitude table is a data table defining altitude values respectively for a plurality of regions 50 being set in a geological formation. An altitude defined table in which the altitude value such as "100 m" is defined, and a non-altitude table in which the altitude value is not defined, are used therefor. Each of the regions 50 is in a rectangle shape capable of being arbitrarily set in size, and the plurality of regions 50 are allowed to be overlapped with another (i.e., overlapping is allowed). Priorities are set so as to correspond to descending order of altitude values defined in respective altitude tables, and storing is carried out according to the priorities, and the retrieving of the altitude table is carried out in the order of the storing, i.e., in the descending order of the altitude values. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
