# Analysis of Mining Waste Dump Site Stability Based on Multiple Remote Sensing Technologies
## 3 Methodology
### Infrared Thermography  
Infrared thermography (IRT) is a science dedicated to the acquisition and processing of thermal information from no-contact measurement devices [49]. According to the electromagnetic radiation theory, any object at a temperature above absolute zero (T > 0 K) emits infrared radiation [50]. Similar to a common camera which forms an image using visible light, a thermographic camera is able to collect infrared radiation and translate it into digital signals with very high temperature resolution in real time [51]. Then, the digital signal is processed based on the thermal contrast between various targets, which by their temperature and emissivity form a thermal image. IRT has been widely used in many applications, such as medicine, building inspection, and nondestructive testing [51; 52; 53; 54]. As well as in the detection of heat distribution, IRT can be used in moisture detection [55].  
Instead of physical temperature, the radiant temperature of an object was obtained by IRT technology. Generally, it is complicated to detect the physical temperature of an object using IRT. Fortunately, knowing the physical temperature of the object is not always necessary. It is sometimes enough to monitor the status of an object merely using the radiant temperature. A thermographic  
Figure 5: The components of the LOS displacements of Point A.  
camera first collected the total radiation energy of the whole illuminated area. Then, the total radiation energy was used to calculate the radiant temperature of the object according to a function model. In fact, aside from collecting the radiation of the object, radiation from the background environment and atmosphere were also collected by the thermographic camera. Therefore, the radiation components from the surrounding environment and atmosphere had to be calibrated. The function model of the total radiation energy, collected by a thermographic camera with the radiant temperature of the object, is expressed by the following equation:  
\[I_{mea}=I(T_{obj})\times\tau\times\varepsilon+I(T_{sur})\times(1-\varepsilon) \times\tau+I(T_{atm})\times(1-\tau) \tag{7}\]  
where \(I_{mea}\) is the total radiation energy collected by a thermographic camera, \(I(T)\) is the radiation energy of a black body when the temperature is T, \(T_{obj}\) is the temperature of the object, \(T_{sur}\) is the surrounding temperature, \(T_{atm}\) is the temperature of the atmosphere between the object and a thermographic camera, \(\varepsilon\) is the average emissivity in the spectrum of a thermographic camera, and \(\tau\) is the average penetration rate of the thermographic camera in the spectrum [56]. Before collecting heat images, parameters such as emissivity, distance between the sensor and object, temperature of the atmosphere, relative humidity and temperature of the surrounding environment had to be inputted into the thermographic camera by the operator [57]. After that, the thermographic camera automatically translated the collected total radiation energy into the radiant temperature of the object according to the above mentioned function model.