Navigation system equipped with portable sub-navigation unit

A navigation method comprising the steps of:

• performing a first route search to produce map information to guide a first movable member carrying a navigation apparatus from a current position to a destination and to produce first-movable-member map information formed by laying route information on the map information;
• and
• performing a second route search to produce further map information to guide a second movable member carrying a portable sub-navigation unit from a further current position to the destination and to produce second-movable-member map information formed by laying further route information on the further map information, the further current position being an instantaneous position at which the second route search is performed.

A program readable by a computer incorporated in a navigation system provides the functions of:

• performing a first route search to produce map information to guide a first movable member carrying a navigation apparatus from a current position to a destination and to produce first-movable-member map information formed by laying route information on the map information;
• and
• performing a second route search to produce further map information to guide a second movable member carrying a portable sub-navigation unit from a further current position to the destination and to produce second-movable-member map information formed by laying further route information on the further map information, the further current position being an instantaneous position at which the second route search is performed.

A navigation system, comprising:

• a navigation apparatus for providing a first movable member with a route guide by showing a route from a current position to a destination;
• and
• a portable sub-navigation unit for providing a second movable member with a further route guide by showing a further route from a further current position to the destination, after the route guide performed by the navigation apparatus.