## 3 Results
### Studies Implementing Vision Systems (VSS)
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Author** & **Target** & **SHM** & **Study Objectives** & **Methods** & **Camera Features** & **Test Scenarios** & **Main Results** \\ \hline
2021 [51] & & & A systematic procedure to estimate building vibration & & & & In the experimental setup, the frequency and amplitude of vibrations were & \\  & & & (amplitude and frequency) by & Single-camera: & & estimated and \\  & & & frequency) by & Hikvision & Experimental: & compared with ground shaking table & truth (infrared sensor), \\ [PERSON] et al., & & & combining cameras and edge computing devices, using & & (features not available), & (indoor) & obtaining an error of \\ [PERSON] et al., & & & & & & In-field: & 0.01 Hz (accuracy: \\ [PERSON] et al., 2022b [48] & Buildings & Displacement estimation (vibration) & & & & & \\  & & & computer vision & mounted on & & building roof & and 12 mm in vibrations were \\  & & & & & & & 93\%). The calculation \\  & & & & vibration signal & & & time was reduced by \\  & & & extraction. & & & & 83.73\%. No results \\  & & & & & & & were provided for \\  & & & & & & & in-field tests. \\ \hline  & & & A solution for & & & & \\  & & displacement estimation based on & & & & & The estimated \\  & & computer vision & & & & displacements agreed \\  & & techniques (template & & & & well with those \\  & & matching and & & iPhone 7 plus & Experimental: & measured by the laser \\  & & & circular Hough & (1920\(\times\)1080 px, 60 & aluminum & transducer system in \\  & & & transform), artificial & & (ps), mounted on a & alloy cantilever & the time domain. The \\  & & & circular targets, and & & tripod 1.5 mm away & plate (indoor) & estimated first and \\  & & & refinement procedure & & from targets. & & second vibration \\  & & & of subpixel & & & frequencies were also \\  & & & localization to & & & & consistent. \\  & & & improve estimation & & & & \\  & & accuracy. & & & & & \\ \hline  & & & & & & The maximum error in displacement was 3 \\ [PERSON] et al., & & & & & Single-camera: & & mm (8.45\%) in static \\
2021 [50] & Bridges & Vibration estimation (from displacement) & System to measure structural displacement using multi-targets data. & CV and active LEDs & DAHUA camera & Experimental: & loading and 5.5 mm \\  & & & & active & (2688 \(\times\) 1520 px, 25 & 2.90\%) in dynamic \\  & & & displacement using displacement using multi-targets data. & LEDs & Hz), mounted on tripod 24 m away & (indoor) & loading tests vs. LVDT. \\  & & & & & tripod 24 m away from the bridge. & & The maximum relative error in vibration frequency was 1.82\% vs. accelerometers. \\ \hline  & & & A contactless approach for indirectly estimating loading forces using a vision-based system with targets. & Single-camera: & & Pearson correlation with loading forces was \\  & & & & & Phantom V9 & beam with & between 0.65 and 0.82 \\  & & & & loading forces using a vision-based system with targets. & (1632 \(\times\) 800 px, 1000 Hz). & (indoor) & using the vision-based system, which was \\  & & & & & (1632 \(\times\) 800 px, 1000 Hz). & (indoor) & lower than that using \\  & & & & & &  accelerometers (0.95) \\ \hline  & & & Damage detection & & Single-camera: & & \\  & & using a UAV-based system on concrete dams through 3D reconstruction and appropriate distribution of ground control points. & & & & \\  & & & & & & \\ \hline  & & & & & & \\ \end{tabular}
\end{table}