Infrared thermography monitoring of rock faces – Potential and pitfalls

Slope-Scale Remote Mapping of Rock Mass Fracturing by Modeling Cooling Trends Derived from Infrared Thermography

“…Using the software Research IR-Max™, we measured the average temperatures of the black tape (T TAPE ) and the rock material (T ROCK ) within circular areas to avoid sample edge effects. Finally, we set the emissivity of the black tape to 0.97 and tuned the rock emissivity until it reached the same recorded temperature (T TAPE = T ROCK = 68.3 • C; Figure 6b) to estimate rock emissivity (ε rock = 0.95); these values were fully consistent with values reported in the literature for rocks with similar composition [71,72,74]. To investigate and incorporate possible effects of topography on the sky radiation contribution (Figure 4) of the reflected temperature component [74], we designed and carried out ad hoc field experiments (Figure 7).…”

“…Finally, we set the emissivity of the black tape to 0.97 and tuned the rock emissivity until it reached the same recorded temperature (T TAPE = T ROCK = 68.3 • C; Figure 6b) to estimate rock emissivity (ε rock = 0.95); these values were fully consistent with values reported in the literature for rocks with similar composition [71,72,74]. To investigate and incorporate possible effects of topography on the sky radiation contribution (Figure 4) of the reflected temperature component [74], we designed and carried out ad hoc field experiments (Figure 7). We wrapped a plastic sphere (diameter of 1 m) in rough aluminum foil, working as an almost perfect infrared reflector (emissivity, ε = 0.03).…”

“…Different contributions are modulated by the target material emissivity [69,72] and the atmospheric transmittance [45,59]. Several authors suggested that the temperature recorded with thermal cameras depends on topography [58,69,73] in outdoor conditions, where significant amounts of energy radiated by the sky and surrounding ground are reflected by the target [74]. In particular, T REFL is mostly influenced by the radiation contribution of the cold sky (Figure 4), characterized by temperature values between −65 • C and −55 • C on clear days [60,75].…”

“…In particular, T REFL is mostly influenced by the radiation contribution of the cold sky (Figure 4), characterized by temperature values between −65 • C and −55 • C on clear days [60,75]. This contribution appears to be stronger in flat topography, resulting in a cooler apparent temperature [74].…”

“…As the Sky IR radiation is vertical (Figure 4), we can consider the local sphere surface inclination as representing the topographic slope (α = 0: horizontal topography). For each To investigate and incorporate possible effects of topography on the sky radiation contribution (Figure 4) of the reflected temperature component [74], we designed and carried out ad hoc field experiments (Figure 7). We wrapped a plastic sphere (diameter of 1 m) in rough aluminum foil, working as an almost perfect infrared reflector (emissivity, ε = 0.03).…”