An Image Measurement Localization Technique for Deformation Monitoring of Engineering Constructions

In order to prompt the further application of the image measurement technique in the deformation monitoring for engineering constructions, this article proposes a new localization solution for the accurate positioning of an artificial mark center in an image taken outdoors in a long range. Most existing localization algorithms based on image measurement only focus on the subpixel positioning part. Different from that, this article studies the pixel-level localization technique and data quality control mechanism. It first introduces the concept of the maximum gradient projection (MGP) to extract edge pixels instead of using traditional gradient operators. Then, an improved edge thinning algorithm is presented and the curvature is used to obtain an integral and reliable pixel-level edge of an object with less sensitivity to the uncertain interferences. Finally, a data quality control system is designed after the subpixel localization of the mark center to select those meeting the statistical requirement. Localization errors caused by various negative effects can thus be controlled. The experimental results show that the proposed deformation monitoring technique based on the image measurement demonstrates its accurate localization performance when facing different natural environment, background, and photographic ranges. It also has fast processing speed and less requirement for imaging equipment. When using a single lens reflex (SLR) with normal lens, it can achieve less than 3.5-mm localization accuracy within the 200-m photographic range. Therefore, it shows its potential in real deformation monitoring applications.