| English term or phrase: a mesh unit | For example, when a navigation device requests differential data for updating map information from a map information distribution center, the navigation device transmits a navigation ID which identifies the aforementioned navigation device and a mesh number for updating map information. The aforementioned map information distribution center compares a version of map information of the mesh stored in the navigation device with that of the latest version based on the navigation ID and mesh number received and, when differential data is available, transmits the differential data to the navigation device. Such map information distribution center is disclosed in Japanese Patent Application Publication No . JP-A-2004-125510 (paragraphs 0032 to 0040 and 0046 to 0063, FIGS. 15 to 18 and 20 to 29), for example.
Also for example, when a navigation device requests differential data for updating map information from a map information distribution center, the navigation device transmits a navigation ID which identifies the aforementioned navigation device and a mesh number for updating map information. The aforementioned map information distribution center compares a version of map information of the mesh stored in the navigation device with that of the latest version based on the navigation ID and mesh number received and, when differential data is available, transmits the differential data to the navigation device. Such
map information distribution system is disclosed in Japanese Patent Application Publication No. JP-A-2004-125510 (paragraphs 0032 to 0040 and 0046 to 0063, FIGS. 15 to 18 and 20 to 29), for example.
However, the map information distribution center described in Japanese Patent Application Publication No. JP-A-2004-125510 manages the version of map information stored in a navigation device of all roads regardless of road categories of high standard roads such as national expressways, city expressways and national roads of single or double digit numbers, ordinary roads such as national roads of triple digit numbers or more, principal local roads, prefectural roads and municipal roads, and narrow streets. For this reason, even while a part of the map information relating to national expressways, city expressways and national roads of single or double digit numbers have been updated to that of the latest version, when a
navigation ID and a mesh number for updating map information are received from a navigation device, it is required to transmit the updating information for the whole roads, not extracting and transmitting the bare minimum amount of differential data to the navigation device. Thus, there have been problems in that the amount of communication data between the map information distribution center and the navigation device becomes large.
Also, in the map information distribution system described in Japanese Patent Application Publication No. JP-A-2004-125510, the mesh number for updating map information is transmitted from the navigation device to the map information distribution center. As the mesh number subject to update is transmitted every time, there have been problems of the amount of communication data by the navigation device and the map information distribution center becomes large. In addition, when the navigation device is updated based on the map information recorded on a storage medium, as the map information distribution center not knowing the current version of map information stored in the navigation device, there have been problems of not being able to extract the differential data of the bare minimum amount and to transmit the data to the navigation device.
According to a fourth aspect of the invention, there is provided the map information distribution center according to any one of the first to third aspects, wherein the map information is divided into a mesh unit of a predetermined region, the version information storage stores the version information for each road category in the mesh unit, and the extracting section extracts the differential data for each road category in the mesh unit.
Further, in a map information distribution center, according to a fourth aspect, as map information is divided into a mesh unit of a predefined region and the map information stored in a navigation device is managed with version information for each road category in the aforementioned mesh unit, and as differential data for each road category between the map information stored in the navigation device and the map information of the latest version is extracted in the mesh unit, it makes it possible to accurately manage the update history of version information for each road category of the map information stored in the navigation device in the mesh unit and to accurately manage version information for each road category of the map information currently stored in the navigation device in the mesh unit. |
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