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THERMAL REMOTE SENSING: CONCEPTS, ISSUES AND APPLICATIONS 
Anupma PRAKASH 
ITC, Geological Survey Division 
prakash@itc.nl 
Working Group WG VII / 3 
KEY WORDS: Thermal infrared, radiant temperature, emissivity, black body, volcanoes, fires. 
ABSTRACT 
In the last few decades remote sensing has reached from an experimental to an operational level. The increase in the 
number of earth observation satellites, the advancement in tools and processing techniques, and the use of data for new 
applications has been phenomenal. However, the major part of the efforts were directed in the past towards the use of 
optical data and now also to the use of microwave data. The available literature underlines the fact that the use of data 
acquired in the thermal infrared region has been relatively limited within the scientific and application community. The 
limited use of thermal data is linked to several facts such as the limitation of the sensor capabilities, the nature of data 
itself, and the reluctance of many to explore the potentials of thermal remote sensing. This paper deals with the concepts 
and issues of thermal remote sensing and presents a variety of applications where thermal data finds its way. The 
benefits and limitations of thermal data are discussed and the potential of thermal remote sensing, specially in light of 
future high resolution satellites, is highlighted. The paper concludes with the author's views on the importance of these 
aspects specially in the standard remote sensing educational programmes. 
1 INTRODUCTION 
Thermal remote sensing is the branch of remote sensing that deals with the acquisition, processing and interpretation of 
data acquired primarily in the thermal infrared (TIR) region of the electromagnetic (EM) spectrum. In thermal remote 
sensing we measure the radiations 'emitted' from the surface of the target, as opposed to optical remote sensing where 
we measure the radiations 'reflected' by the target under consideration. Useful reviews on thermal remote sensing are 
given by Kahle (1980), Sabins (1996) and Gupta (1991) 
It is a well known fact that all natural targets reflect as well as emit radiations. In the TIR region of the EM spectrum, 
the radiations emitted by the earth due to its thermal state are far more intense than the solar reflected radiations and 
therefore, sensors operating in this wavelength region primarily detect thermal radiative properties of the ground 
material. However, as also discussed later in this article, very high temperature bodies also emit substantial radiations at 
shorter wavelengths. As thermal remote sensing deals with the measurement of emitted radiations, for high temperature 
phenomenon, the realm of thermal remote sensing broadens to encompass not only the TIR but also the short wave 
infrared (SWIR), near infrared (NIR) and in extreme cases even the visible region of the EM spectrum. 
Thermal remote sensing, in principle, is different from remote sensing in the optical and microwave region. In practice, 
thermal data prove to be complementary to other remote sensing data. Thus, though still not fully explored, thermal 
remote sensing reserves potentials for a variety of applications. The next sections discuss the main concepts and issues 
of thermal remote sensing and continue to present a brief overview of the application of thermal data. The article 
concludes with the advantages and limitations of thermal remote sensing and the need for including this topic in remote 
sensing educational programmes. 
2 CONCEPTS 
In thermal remote sensing, radiations emitted by ground objects are measured for temperature estimation. These 
measurements give the radiant temperature of a body which depends on two factors - kinetic temperature and 
emissivity. Figure 1 presents the various factors affecting the radiant temperature and these are further discussed in 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 239