ABSTRACT
Remote sensing is, in general, the collecting of information from an object without making direct physical contact with it. The term is usually used in a more restricted sense in which the observation is made from above the object of interest, from a sensor carried on an airborne or spaceborne platform, and the information is carried by electromagnetic radiation, i.e. visible light, infrared or ultraviolet radiation, or radio waves (Rees 2001, 2006). This radiation can occur naturally, in which case the type of remote sensing is said to be passive, or it can be transmitted from the sensor to the object under investigation, in which case the remote sensing is said to be active. Passive remote sensing developed originally from aerial photography, and can be thought of as an extension of the idea of aerial photography to include other parts of the electromagnetic spectrum, other technologies for detecting the radiation and storing the data, and other platforms to carry the sensor. Active remote sensing grew from the military development of radar during the Second World War.
