Electronic navigation system and method

1. A method for providing improved navigation services to a plurality of mobile units, the method comprising:

from the mobile unit, transmitting a request for a route between an origin and a destination to a base unit;

on the mobile unit, receiving said route from the base unit;

on the mobile unit, comparing the received route with on-board map information stored on the mobile unit;

if a portion of the route is not covered by the on-board map information, from the mobile unit, transmitting a request for a strip map for a geographic area corresponding to the portion of the route not covered by the on-board map information to said base unit, said strip map includes data representing roads, side roads, intersections and points of interest in said geographic area corresponding to the portion of the route not covered by the on-board map information; and

in said mobile unit, receiving said strip map.

2. The method of claim 1 wherein said portion of the route not covered by the on-board map information is in terms of a geographic scope.

3. The method of claim 1 wherein said portion of the route not covered by the on-board map information is in terms of a geographic bound.

4. The method of claim 1 wherein said portion of the route not covered by the on-board map information is in terms of a level of detail.

5. The method of claim 1 wherein said portion of the route not covered by the on-board map information is in terms of a level of content.

6. A system for providing geographic information comprising:

a mobile unit having a first geographic database containing first map data representing roads, intersections and points of interest in a geographic area;

a base unit having a second geographic database containing more up-to-date map data representing roads, intersections and points of interest in the geographic area than said first geographic database, wherein said base unit is located remote from said mobile unit; and

a communications link to transmit a request from the mobile unit to the base unit and to transmit a response from the base unit to the mobile unit;

wherein said mobile unit

transmits a request for a route to a base unit,

receives the route from the base unit,

compares the route with first map data stored on the mobile unit;

if a portion of the route is not covered by the first map data, transmits a request for a map update for a geographic area corresponding to the portion of the route not covered by the first map data to said base unit, said map update includes data representing roads, side roads, intersections and points of interest in said geographic area corresponding to the portion of the route not covered by the first map data.

7. The system of claim 6 wherein said communications link is a cellular telephone system.

8. The system of claim 6 wherein said map update response comprises a strip map.

9. The system of claim 6 wherein said mobile unit includes a navigation application program that determines whether updated map data is required to provide a navigation function.

10. The system of claim 9 wherein said navigation function comprises calculation of a route between an origin and a destination.

11. The system of claim 9 wherein said navigation function comprises obtaining a requested point of interest.

12. The system of claim 9 wherein said navigation function comprises route guidance between an origin and a destination.

13. The system of claim 9 wherein said navigation function comprises a map display.

14. The system of claim 9 wherein said mobile unit receives said map update response and uses said up-to-date map data representing roads, intersections and points of interest in the portion of the geographic area to provide said navigation function.