A Review of Temperature and Emissivity Retrieval Methods: Applications and Restrictions

Remote data coming from the Thermal InfraRed (TIR) region of electromagnetic spectrum has several applications in geology, climatology, energy balance, biological and geophysical process analysis, disaster assessment and change detection analysis. In the TIR region, the emission of the targets is dominant when compared with reflection. This radiation is a function of two unknowns – the emissivity and the temperature of the target. To study TIR, a precise retrieval of the temperature and/or emissivity from the measured radiation is necessary. This process is usually difficult due to a non-linear relationship between these two unknowns and the measured radiation. In the last 40 years, several researchers have developed approaches to generate reliable results. However, all these methods have constraints in their applications. This paper reviews the advantages and disadvantages of the main methods of temperature and emissivity separation in order to create a summary that allows the researchers to choose the most suitable method in their own application.