Image positioning method and image positioning device for using the same

An image positioning device, which installed in a vehicle that is driving on a road, and a plurality of signs is sequentially arranged on the road in a direction that the vehicle moves, and the image positioning device comprising:

• an image retriever sequentially retrieving an n-th positioning image and an (n+1)-th positioning image of the signs closest to the vehicle, and n is a natural number, and the image retriever generates driving signals when the image retriever retrieves the n-th positioning image and the (n+1)-th positioning image;
• a storage storing an electronic map, and the electronic map has a plurality of paths, a plurality reference images, and characteristic positions of the plurality of paths and the plurality reference images, and the characteristic positions of the plurality of reference images correspond to the characteristic positions of the plurality of paths;
• a displacement detector electrically connected to the image retriever and receiving the driving signals, and the displacement detector detects a displacement that the vehicle moves within a period between two time points when the displacement detector receives the driving signals;
• and
• a processor electrically connected to the image retriever, the storage, and displacement detector, and the processor searches the reference images identical to the n-th positioning image on the electronic map, uses the reference images identical to the n-th positioning image as n-th characteristic images, searches the reference images identical to the (n+1)-th positioning image on the electronic map according to the electronic map, the displacement, and the characteristic positions of the n-th characteristic images, uses the reference images identical to the (n+1)-th positioning image as (n+1)-th characteristic images, orders all the characteristic images corresponding to each other according to their searched time to establish characteristic image sequences, and orders all the positioning images according to their retrieved time to establish a positioning image sequence, and when number of the characteristic image sequences that correspond to the positioning image sequence is one, the processor estimates a position of the vehicle according to the displacement, the electronic map, the path corresponding to the positioning image sequence, and the characteristic positions of the n-th characteristic image and the (n+1)-th characteristic image, wherein the characteristic image sequence includes the n-th characteristic image and the (n+1)-th characteristic image, the n-th characteristic image and the (n+1)-th characteristic image of the characteristic image sequence are sorted in order of time of searching the n-th characteristic image and the (n+1)-th characteristic image, the positioning image sequence includes the n-th positioning image and the (n+1)-th positioning image, and the n-th positioning image and the (n+1)-th positioning image of the positioning image sequence are sorted in order of time of retrieving the n-th positioning image and the (n+1)-th positioning image.