Pixel Measurement for Cracks in Concrete Construction

In this paper a new measurement method is developed to measure the length and width of the cracks in concrete construction. The new method is based on the optical measurement and image processing techniques. Firstly original images are preprocessed for calculation. Then calibration of pixel on the basis of the theory of correlation of digital speckle is to get the real size of one pixel. The length of crack is searched and calculated in pixel accuracy and width in sub-pixel accuracy. Finally texting experiments and field experiment are conducted to verify that the precision of the method meets the engineering requirements. It is an accurate, automatic and noncontact measurement method.