3. Energy Interactions with the Atmosphere and Earth’s Surface

The spectral response of a target measured by a remote sensor is determined by the way electromagnetic radiation interacts with the target. This unit will outline the main interactions of electromagnetic radiation with the atmosphere, the environment, and with soils, water and vegetation in particular. Knowledge of the factors controlling radiation interaction can help substantially in the analysis of remotely sensed data and so it is important that the basic principles are understood.

In 3.2, we look at the different sources of electromagnetic radiation used in remote sensing, distinguishing between natural and artificial sources of radiation. We look particularly at how the characteristics of a source – particularly its temperature – influence what we can achieve using remote sensing. We then move on in 3.3 to look at the way that the atmosphere affects incoming and outgoing radiation and how processes such as atmospheric scattering and absorption influence electromagnetic radiation as it passes through the atmosphere. Finally, in 3.4 we move on to look at the Earth’s surface and how radiation interacts with different types of surface, a key concept underpinning all terrestrial applications of remote sensing.

The focus in this unit is on the principles that lie behind modern-day remote sensing, but it is necessary to understand these principles before moving on to look at specific techniques in practice.

Reading

In preparation for the materials that follow, we recommend that you read either Sections 1.2 through 1.4 of Mather and Koch (2011) or Sections 2.5 – 2.7 of Campbell and Wynne (2011):

Campbell, J.B. and Wynne R.H (2011): Introduction to Remote Sensing. 5th Edition. The Guilford Press, New York.

Mather, P.M. and Koch M (2011): Computer processing of remotely sensed images – an introduction.4th Edition. Wiley and Sons, Chichester.