Monitoring Instantaneous Dynamic Displacements of Masonry Walls in Seismic Oscillation Outdoors by Monocular Digital Photography

Figure 3

Schematic diagram of photographing scale transformation: H1 is the focal length of a CCD camera, H2 is the distance between the optical origin (o) and the front end of the CCD camera, D1 on reference plane and D2 on the object plane are the real-world lengths formed by the view field of the CCD camera at photographing distances H3 and H4, respectively, and N is the maximal pixel number in a horizontal scan line of an image plane, which is fixed and known a priori irrelevant to the photographing distances.