By extracting checkerboard corners with Harris algorithm

a symmetry algorithm was proposed to identify the all inner-corners and eliminate outercorners and false corners of the checkerboard form primal corners muster. The method based on gray gradient was adopted for accurately extracting checkerboard corners. To distinguish the outer loop corners and automatic locate the corners form the corners muster of the checkerboard

a new method based on convex hull was presented

which can loop by loop recognize and sort all the corners. As a result

the image dots can be automatically matched with its corresponding physical dots

thus

parameters of camera were automatically and accurately calibrated. Experiments shows the method has high precision and preferable robust

and is especially adapted for the automatic online camera calibration.