A comprehensive alleviation technique for optical‐turbulence‐induced errors in vision‐based displacement measurement

Structural Control and Health MonitoringVolume 27, Issue 3 e2496 RESEARCH ARTICLE A comprehensive alleviation technique for optical-turbulence-induced errors in vision-based displacement measurement Longxi Luo, Corresponding Author Longxi Luo longxi.luo@gmail.com orcid.org/0000-0003-2661-4177 Department of Civil Engineering, Tsinghua University, Beijing, China Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York Correspondence Longxi Luo and Jianping Wu, Department of Civil Engineering, Tsinghua University, Beijing 100084, China. Email: longxi.luo@gmail.com; jianpingwu@tsinghua.eduSearch for more papers by this authorMaria Q. Feng, Maria Q. Feng Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New YorkSearch for more papers by this authorJianping Wu, Corresponding Author Jianping Wu jianpingwu@tsinghua.edu Department of Civil Engineering, Tsinghua University, Beijing, China Correspondence Longxi Luo and Jianping Wu, Department of Civil Engineering, Tsinghua University, Beijing 100084, China. Email: longxi.luo@gmail.com; jianpingwu@tsinghua.eduSearch for more papers by this author Longxi Luo, Corresponding Author Longxi Luo longxi.luo@gmail.com orcid.org/0000-0003-2661-4177 Department of Civil Engineering, Tsinghua University, Beijing, China Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York Correspondence Longxi Luo and Jianping Wu, Department of Civil Engineering, Tsinghua University, Beijing 100084, China. Email: longxi.luo@gmail.com; jianpingwu@tsinghua.eduSearch for more papers by this authorMaria Q. Feng, Maria Q. Feng Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New YorkSearch for more papers by this authorJianping Wu, Corresponding Author Jianping Wu jianpingwu@tsinghua.edu Department of Civil Engineering, Tsinghua University, Beijing, China Correspondence Longxi Luo and Jianping Wu, Department of Civil Engineering, Tsinghua University, Beijing 100084, China. Email: longxi.luo@gmail.com; jianpingwu@tsinghua.eduSearch for more papers by this author First published: 15 December 2019 https://doi.org/10.1002/stc.2496Citations: 8Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Summary Computer vision-based displacement measurement techniques can be affected by the optical turbulence in the field in hot weather. The optical turbulence can be observed naturally when viewing a thick layer of heated air. The nonuniform density distribution of the air due to heat creates spatial variations in refraction indexes, resulting in distortions in video images and measurement errors in displacements obtained from distorted videos. The effect of optical turbulence on vision-based displacement sensing is first illustrated in the field test conducted in hot weather. Then, the statistical characteristics of the optical-turbulence-induced measurement errors are analyzed and confirmed. And a comprehensive optical-turbulence error alleviation technique, which has two steps, is designed based on the statistical studies. A previously developed high-performance multitarget vision-based displacement measurement technique is utilized in the first step to track multiple targets. Distortions of multiple targets are estimated simultaneously continuously. Targets with the least distortions in each frame are identified and their displacements are extracted as the primary displacement. To further alleviate errors in the primary displacement, an adaptive optical-turbulence error filter is formulated in the second step based on the statistical characteristics of the optical-turbulence errors. Validations of the optical-turbulence error alleviation technique are performed in both laboratory and field tests. Field tests are conducted on the Williamsburg Bridge in the natural environment. After alleviating optical-turbulence and camera vibration errors, frequency domain analyses are conducted on vibrational displacements of the Williamsburg Bridge in response to train passing. Citing Literature Volume27, Issue3March 2020e2496 RelatedInformation