## 3 Results
### Systematic Content Review Results for Sensors Monitoring Mine Tailings Storage Facilities
#### 3.3.1 Content-Based Data Perspective Analysis
\begin{table}
**Sensor Name** & **Sensor Typology** & **Data Obtained/ Variable Measured** & **Monitoring Results** & **Monitoring Frequency** & **Real-Time Monitoring** \\ \hline Visual inspection by miners & & Dam performance & Interior/exterior, medium reliability, low cost & 1/week & No \\ \hline Visual inspection by EoR & & Dam performance & Interior/exterior, medium reliability, low cost & 1/month & No \\ \hline DSR inspection & Photographic inspection & Dam performance & Interior/exterior, high reliability, high cost & 1/year & No \\ \hline ITRB inspection & (observational method) & Dam performance & Interior/exterior, high reliability, high cost & 1/3 years & No \\ \hline Closed-circuit television camera (CCTV) & & Dam performance & Interior/exterior, high reliability, low cost & Every minute & Yes \\ \hline Meteorological station & & Rain/wind/ evaporation/solar radiation & Interior/exterior, high reliability, low cost & Every minute & Yes \\ \hline Accelerometer & & 1D/2D/3D seismic accelerations & Interior/exterior, point, high reliability, medium cost & On event & Yes \\ \hline Slope indicator/inclinometer & & 1D/2D displacement/slope & Interior/exterior, point, high displacement/slope & 4/month & Yes \\ \hline Extensometer & & 1D displacement & Interior/exterior, point, high reliability, low cost & 4/month & Yes \\ \hline Casagrande piezometer & & Hydraulic head/pore water pressure & Interior, point, high reliability, low cost & 1/week 1/month & No \\ \hline Vibrating wire piezometer & Geotechnical instrumentation & Hydraulic head/pore water pressure & Interior, point, high reliability, medium cost & Real time & Yes \\ \hline Tiltmeter & & 2D displacement & Interior/exterior, point, high reliability, low cost & 4/month & Yes \\ \hline Settlement cell & & 1D displacement (vertical) & Interior/exterior, point, high reliability, low cost & 2/month & Yes \\ \hline Distributed optical fiber strain sensors & & 1D displacement (strain), acoustics & Interior/exterior, feature, high initial cost for permanent monitoring, achievable accuracy: 10–5 mm/m & & \\ \hline Distributed optical fiber temperature sensors & & 1D temperature & Interior/exterior, leak and seepage detection/localization & & \\ \hline Monitoring wells & & & & \\ \hline Seepage with weir or flume & Hydraulic instrumentation & Seepage flow & Seepage condition & Real time & Yes \\ \hline Water quality & & Metals content & Leak and seepage detection/localization & 4/month & Yes \\ \hline Surveying (optical) & & 3D displacement & Exterior, point/ feature, e.g., level profile surveys, labor-intensive & 6/year & No \\ \hline Automated total stations (ATS) & & & & \\ \hline \
\begin{tabular}{p{113.8 pt} p{113.8 pt}} Automated total stations (ATS) &
\begin{tabular}{p{113.8 pt}} Topographical/ bathymetrical/ geodetic devices (remote sensing) \\ (GPS)/Global navigation satellite system (GNSS) \\ \end{tabular} & 3D displacement & Exterior, point/ feature, high accuracy, low labor costs, sub-cm accuracy for distances \textless{1 km} & 12/year & No \\ \hline Global positioning system (GPS)/Global navigation satellite system (GNSS) & & & & \\ \hline Secondary surveillance radar (SSR) & & & & \\ \hline \end{tabular}
\end{table} 
Table 6: Comparison of different monitoring technologies for structural health and safety management monitoring in TSFs. The sensor instrumentation reviewed in Table 6 is classified as either invasive instrumentation, which breaks into a location and destroys or modifies the measured object, or non-invasive instrumentation, which does not break into a location and, therefore, does not destroy or modify the measured object. Figure 23 shows an example of the typical location and installation of invasive sensor instrumentation in a TSF dam. Due to their extensive application and the availability of information, the details of the most traditional invasive instrumentation types are not presented in this review, as they are already described in other articles in the literature.