A Dual-marker Crack Monitoring System Based On Image Processing

Cracks are an important reference indicator in structural health monitoring,and their development degree and development trend are of great significance in the identification and structural repair of dangerous buildings.This paper combines digital image processing technology with traditional crack marker measurement technology,studies the marker image detection algorithm for building crack measurement,marker-based camera calibration method and marker-based tilt photography correction method,through indoor simulation experiments and The field test proves the effectiveness and practicability of the research algorithm in this paper,and realizes the establishment of an online crack change measurement website service system,which will provide a new measurement method and reference data for the health monitoring and evaluation of various buildings.The main research results of this paper are as follows:(1)A new type of crack measurement marker combination was designed according to the commonly used principle of crack measurement markers for white iron sheets.The markers are checkerboard type and QR code type,because both have easy-to-identify corners.Point model and graphic characteristics,so it can be accurately separated from the complex crack image by digital image technology.(2)Use the improved growth-based checkerboard recognition algorithm to extract the corners of the checkerboard markers,calculate the response values of the checkerboard image pixels according to the corner model and non-maximum suppression algorithm,and draw the checkerboard corners by the response values The approximate position of the point is calculated and sub-pixel level calculation and chessboard growth are performed,and features such as the area and perimeter of the chessboard are screened to avoid background interference and liquidation,and the precise position of the corner points of the chessboard is finally determined.(3)A method of calculating the crack change based on the change of the corner of the marker is proposed.This method regards the plane where the crack is located as a rigid body,uses the image to establish a plane coordinate system,and finally analyzes the change of the corner based on the multiple images taken before and after.For horizontal translation,longitudinal translation and rotation,the development of cracks is calculated according to the coordinate changes.(4)Developed a set of online system for crack change measurement and management.The system uses WEB technology to embed all the algorithms in this article on the server.Users can easily measure and manage crack changes according to system prompts,which provides information for crack change measurement a brand new technical means.