ABSTRACT
Optical methods have an important role in remote sensing technology. These techniques can be divided into active and passive methods, depending on whether or not the person making the measurement first transmits a signal as part of the measurement process. To a certain extent, any activity in which a telescope or a camera or even just the human eye is used to view some object at a distance can be considered to be a form of passive remote sensing. If a variety of physical parameters can be determined by measuring spectral information about radiation coming from the object. It is possible to obtain global information of this kind by using aeroplanes or satellites.
