The invention provides a measuring method for performing monitoring measurement on two or more objects. The method includes a step of scanning a predetermined range so as to include two or more objects to be measured, a step of acquiring digital images at a predetermined time interval so that there are two or more images which include the same object to be measured while scanning, a step of detecting an image of the object to be measured in the digital image and of setting up a minimal rectangle surrounding the image of the object to be measured, and a step of overlapping the minimal rectangles obtained in two or more digital images and of carrying out integrated processing to obtain positions of the objects to be measured in the image. The composite directional angle of each object to be measured is obtained based on the results of the integrated processing.