Method of making update information of map data and differential data of map data updating system

A method of generating update information of map data for a differential update system comprising an electrical device including a storage medium for storing map data containing plural graphic data sets, each of the graphic data sets being generated as a shape point coordinate train graphic data, and the map data being generated from an original map database, the method comprising:

• generating a first original map database including graphic data so that permanent identification information is associated with each graphic data set, the identification information being unique to each graphic data set and permanent;
• manipulating the first original map database to generate a first map data, and recording the first map data into the storage medium, wherein a first administration information including the identification information being unique to each graphic data set and permanent;
• generating second original map database based on the first original map database so that the same permanent identification information are associated with graphic data located at the same position between the first original map database and the second original map database;
• manipulating the second original map database to generate a second map data, and recording the second map data into a storage medium, wherein a second administration information including the identification information of the graphic data set in the storage medium is generated, the identification information and the storage position is associated with each other in the second administration information;
• comparing the first original map database with the second original map database, and generating differential data indicating which of the graphic data sets are being updated and how the graphic data sets are being updated, the graphic data sets being identified by the identification information;
• and
• generating update information for the first map data generated by manipulating the first original map database, the update information being generated based on the administration data and the administration information generated when the first map data is generated by manipulating the first original map database, the update information indicating which graphic data sets in the storage medium arc being updated and how the graphic data sets are updated, and the graphic data sets being identified by the storage position in the storage medium.

A method of generating graphic data update information included in map data stored in a map storage medium, comprising steps of:

• assigning an identification number unchanging between new original map data and old original map data to graphic data included in original map data that is used as a basis of the map data stored in the map storage medium;
• generating administration information that correlates storage position information of the graphic data in the map storage medium and the unchanging identification number, when generating the map data from the original map data;
• and
• generating the update information for the graphic data included in the map data stored in the map data storage medium by using the administration information and differential information between the new original map data and the old original map data.