One of the major achievements of human beings is the ability to record observational data in the form of photographs, a science which dates back to 1826. Humans have always tried to reach greater heights (treetops, mountains, platforms, and so on) to observe phenomenon of interest, to decide on habitable places, farming and such other activities. Curiosity motivates human beings to take photographs of the earth from elevated platforms. In the initial days of photography, balloons, pigeons, and kites were used to capture such photographs. With the invention of the aircraft in 1903, the first aerial photograph on a stable platform was made possible in 1909 [120]. In the 1960s and 1970s, the primary platform that was used to carry remote sensing instruments shifted from aircraft to satellites [120]. It was during this period that the word ‘remote sensing’ replaced the frequently used word ‘aerial photograph’. Satellites can cover wider land space than planes and can monitor areas on a regular basis.

The new era in remote sensing began when the United States launched the first earth observation satellite called earth resources technology satellite (ERTS-1) dedicated primarily for land observation [120]. This was followed by many other satellites like Landsat 1-5, satellite pour l’ observation de la terre (SPOT), Indian remote sensing (IRS), Quickbird, Ikonos, etc. Change in image format from analog to digital was another major step towards the processing and interpretation of remotely sensed data [120]. The digital format made it possible to display and analyze imagery using computers, a technology that was also undergoing rapid change during this period. Due to the advancement of technology and development of new sensors, the capture of the earth's surface through different portions of the electromagnetic spectrum is possible these days. One can now view the same area by acquiring the data as several images in different portions of the spectrum, beyond what the human eye can view. Remote sensing technology has made it possible to see things occurring on the earth's surface which may not be detected by the human eye.

The formal definition of remote sensing can be given as follows [120]: it refers to the sensing of the earth's surface from space by making use of the properties of electromagnetic waves emitted, reflected or diffracted by the sensed objects, for the purpose of improving natural resource management, land use and the protection of the environment.