In addition, when there are at least four groups of the moving traces MT, the computing device can perform the method of obtaining the boundary line BL disclosed in FIG. 3(b), which is obtaining two boundary lines BL based on the four groups of the moving traces MT, and then using the area enclosed by the two boundary lines BL and two reference lines L1 and L2 as the detection zone DZ.

According to the methods of obtaining the boundary line disclosed in FIGS. 3(a) and 3(b), the computing device can then obtain the detection zone DZ based on the boundary lines BL. As for the example shown in FIG. 1, the detection zone DZ is in the car lane in which vehicles are traveling, and the boundary lines BL are the lines that overlapping or adjacent to the car lane line.

After obtaining the detection zone DZ, the method of obtaining the detection zone DZ continues to step S07 to display the detection zone DZ and another image by a display device, with said another image different from the plurality of images and associated with the image acquiring scene, wherein said another image is preferably a real-time image with the detection zone DZ applied. The display device is, for example, a display screen provided in a monitoring center, the present disclosure is not limited thereto.