Navigation Device, Navigation Method and Navigation System

摘要

A navigation device receives a differential map data from a map delivery server via a communication line. The map delivery server checks whether there is a new intersection on a navigation route searched by the navigation device after updating a map data. The navigation device acquires a differential map data containing the intersection from the map delivery server. Then, an update map data selection section determines whether the intersection can be updated in time. An update order determination section updates the differential map data which can be updated in time in ascending order of time required to reach the intersection.