Radiometric Correction of Landsat TM Data

Typically, when one acquires remotely-sensed data for academic or commercial purposes it is unsuitable for immediate use. That is, several types of corrections must be applied. One set of corrections that is crucial to the use of remotely-sensed data, particularly in quantitative geography, is known as radiometric correction. Though there are many classes of radiometric corrections, this paper will focus on the following three: sensor related corrections, earth-sun distance correction and solar zenith angle corrections, and atmospheric corrections. Sensor related effects refer to sensor-specific changes in the data when a remote sensor converts the incoming radiance to digital numbers. Earth-sun distance corrections account for differences in illumination due to the varying distance of the earth from the sun. Similarly, solar zenith angle corrections account for illumination differences due to variations in the apparent position of the sun relative to the earth. Finally, atmospheric corrections adjust the attenuating and/or scattering effects of the earth's atmosphere on electromagnetic radiation. We will see through example exactly what these corrections do and why they are necessary vis-à-vis their application to remotely-sensed data of the city of Ottawa, Canada.…