| 摘要 |
In a road map data generation apparatus, existing primary road map data is subjected to a deletion process according to a deletion rule to delete a portion of the data. Thus, reduced road map data is generated for a storage medium such as a memory card having a data volume smaller than the primary road map data. A navigation apparatus using the reduced road map data stored in the memory card records a restoration rule pairing with the deletion rule. Based on the restoration rule, the reduced road map data can be restored to the primary road map data. Thus, the deletion rule can decrease the data volume of the primary data to thereby generate the reduced data, whereas the restoration rule can restore the reduced data to the primary data in the navigation apparatus. This helps prevent worsening of the quality of the road map data and lowering of the user's satisfaction.
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