Method of using road signs to augment global positioning system (GPS) coordinate data for calculating a current position of a personal navigation device

1. A method of using road signs to augment Global Positioning System (GPS) coordinate data for calculating a current position of a personal navigation device, the method comprising:

obtaining recent GPS coordinate data with the personal navigation device;

obtaining a real-time image from a camera of the personal navigation device while the personal navigation device is changing its current position, the real-time image showing areas surrounding a road on which the personal navigation device is traveling;

recognizing a road sign in the real-time image by performing image processing on the real-time image; and

using a known position of the road sign to augment the recent GPS coordinate data in order to more precisely determine the current position of the personal navigation device.

2. The method of claim 1 , wherein the road sign is listed in a sign database, the sign database comprising a list of road signs along with corresponding locations and properties of the road signs.

3. The method of claim 2 , wherein the road sign is recognized by comparing a shape of the road sign to shapes of road signs in the sign database.

4. The method of claim 2 , wherein the road sign is recognized by comparing a color of the road sign to colors of road signs in the sign database.

5. The method of claim 2 , wherein the road sign is recognized by comparing text present on the road sign to text of road signs in the sign database.

6. The method of claim 2 , wherein the road sign is recognized by comparing arrows present on the road sign to arrows of road signs in the sign database.

7. The method of claim 2 , wherein the road sign is recognized by comparing an approximate location of the personal navigation device as provided by the recent GPS coordinate data to locations of road signs in the sign database.

8. The method of claim 1 , wherein the known position of the road sign is used in conjunction with a predicted location of the personal navigation device to determine the current position of the personal navigation device when more than one predicted location is calculated by the personal navigation device.

9. The method of claim 1 , wherein the known position of the road sign is used to perform a dead reckoning position calculation when no GPS signals are received by the personal navigation device.

10. The method of claim 1 , wherein the camera is a video camera for continuously obtaining real-time images.

11. A personal navigation device calculating a current position of the personal navigation device using road signs to augment received Global Positioning System (GPS) coordinate data, the personal navigation device comprising:

a GPS receiver for obtaining recent GPS coordinate data;

a camera for obtaining a real-time image while the personal navigation device is changing its current position, the real-time image showing areas surrounding a road on which the personal navigation device is traveling; and

a processor for recognizing a road sign in the real-time image by performing image processing on the real-time image, and using a known position of the road sign to augment the recent GPS coordinate data in order to more precisely determine the current position of the personal navigation device.

12. The personal navigation device of claim 11 , further comprising a sign database, the sign database comprising a list of road signs along with corresponding locations and properties of the road signs.

13. The personal navigation device of claim 12 , wherein the processor recognizes the road sign by comparing a shape of the road sign to shapes of road signs in the sign database.

14. The personal navigation device of claim 12 , wherein the processor recognizes the road sign by comparing a color of the road sign to colors of road signs in the sign database.

15. The personal navigation device of claim 12 , wherein the processor recognizes the road sign by comparing text present on the road sign to text of road signs in the sign database.

16. The personal navigation device of claim 12 , wherein the processor recognizes the road sign by comparing arrows present on the road sign to arrows of road signs in the sign database.

17. The personal navigation device of claim 12 , wherein the processor recognizes the road sign by comparing an approximate location of the personal navigation device as provided by the recent GPS coordinate data to locations of road signs in the sign database.

18. The personal navigation device of claim 11 , wherein the processor uses the known position of the road sign in conjunction with a predicted location of the personal navigation device to determine the current position of the personal navigation device when more than one predicted location is calculated by the processor using the recent GPS coordinate data.

19. The personal navigation device of claim 11 , wherein the processor uses the known position of the road sign to perform a dead reckoning position calculation when the GPS receiver receives no GPS signals.

20. The personal navigation device of claim 11 , wherein the camera is a video camera for continuously obtaining real-time images.