Patent ID: 8224795

Claim:
A computer-implemented method utilizing a computer processor for processing map data in a map data processing apparatus, the method comprising steps of: confirming that a recording medium is loaded at the map data processing apparatus, the recording medium having stored thereon the map data divided into a plurality of divisions and map data management information indicating specific storage positions of the plurality of map data divisions in the recording medium; storing identification information, which bears an initial value indicating that the map data management information used in the map data processing apparatus is stored in the recording medium, into a first nonvolatile memory; storing update data obtained to update part of the map data in units of individual divisions into a second nonvolatile memory, obtaining the map data management information from the recording medium, altering part of the management information corresponding to the update data so as to indicate a storage position of the update data in the second nonvolatile memory, storing the management information into a third nonvolatile memory, and altering the identification information stored in the first nonvolatile memory to indicate that the map data management information is stored in the third nonvolatile memory; obtaining the identification information to ascertain whether the map data management information is stored in the recording medium or in the third nonvolatile memory by accessing the first nonvolatile memory when accessing the map data; obtaining the map data management information from the recording medium when the map data management information is determined as being stored in the recording medium; obtaining the map data management information from the third nonvolatile memory when the map data management information is determined as being stored in the third nonvolatile memory; and accessing the map data based upon the obtained map data management information.