| 摘要 |
Map data is divided into meshes of a prescribed size. Treating four meshes as one group, mesh numbers are assigned to the meshes following an N pattern. After numbers are assigned to the four meshes, these four meshes are collected as one, and numbers are assigned to respective meshes following an N pattern. The map data storage medium stores the map data according to mesh number. As a result, data portions for areas located in close proximity are positioned in close proximity in the map database (storage medium), to thereby improve access efficiency.
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