# Image-Based Structural Health Monitoring: A Systematic Review
## 2 Materials and Methods  
Systematic literature reviews (SLR) can reveal gaps in the literature, highlight notions that are widely accepted but lack empirical evidence, and aid in assessing the quality of research being conducted on a certain issue [26]. Hence, all relevant study questions or topic areas in the available literature must be rationally identified, examined, and interpreted [27]. This paper uses the 2020 Preferred Reporting Items for Systematic Reviews (PRISMA 2020) methodology [28].  
A research question should be developed as a starting point [29], which must be theoretical, empirical, nomothetic, probabilistic, and causal [30]. Three research questions (RQs) were developed for this study and are provided as follows:RQ1: \"What are the thematic purposes and implementation of image-based SHM and how to successfully employ them?\"  
RQ2 \"If image-based SHM systems and devices are tailored to fit the requirements set before their implementation, what are its distinct and frontline features?\"  
RQ3: \"What are the innovations that solve difficulties expected in image-based monitoring?\"  
Popular databases and criteria for searching studies must be decided. The current methodology considered the exploration and investigation of studies in Scopus and ScienceDirect from Elsevier, Google Scholar, MDPI, Springer, Wiley Online and ASCE Library, IOP Science, IEEE, and other databases with a reliable peer review process. Articles, conference papers, reviews, book chapters, and conference reviews are used as primary sources of information. The PICOC (Population, Intervention, Comparison, Outcome, and Context) criteria were then utilized to guide the selection of keywords to be used to query all databases [31]. The keywords that were selected are listed below.  
\"SHM\" OR \"Image Monitoring\" OR \"Structural Monitoring\" OR \"Structural Health Monitoring\" AND \"Technology\" AND \"DEVICE\" AND \"Implementation\" OR \"Applications\" OR \"INNOVATIONS\" OR \"Computer Vision\"  
The next step is to filter the identified papers for further investigation by defining the inclusion and exclusion criteria before conducting the review to prevent bias [31]. The following are the inclusion and exclusion criteria developed and specified for this study.  
1. Period (Inclusion: 2001-2023; Exclusion: Documents before 2001)
2. Language must be English (Inclusion: translated version is available; Exclusion: translated version is not available)
3. Type of document or literature (Inclusion: Articles, Conference Papers, Reviews, Book Chapters, Conference Reviews; Exclusion: Otherwise)
4. Accessibility (Inclusion: Full-text available (In cases where access to the included journal is unavailable, the copy of the manuscript is requested directly from the authors); Exclusion: Otherwise)
5. Relevance to RQs (Exclusion: Not relevant to at least two RQs)  
The Zotero reference management software was then used to automatically identify and reject items that appeared in more than one database. A total of one-hundred and nine (109) papers were selected for data extraction, assessment, and synthesis. Figure 1 depicts a thorough illustration of the methodology employed in this paper.  
Figure 1: Identification, Screening, and Inclusion Process.