Remote sensing (RS) technology has been developed well
ahead of GIS technology. RS acquires information about
material objects from measurements made at a distance,
without coming into physical contact with the object. Usually
an aircraft or satellite does the process. Remote sensing
technology may be divided into three phases: (i) data
collection from a sensor mounted on a platform eg. a satellite;
(ii) data handling; (iii) data interpretation which end up in
generating some thematic maps of the investigated surfaces. A
remote sensing system using electromagnetic radiation has
four components - a source, interactions with the earth's
surface, interaction with the atmosphere and a sensor. The
source of electromagnetic radiation may be natural, like the
sun's reflected light or the earth's emitted heat, or man-made
microwave radar. Earth's surface interaction, that is the
amount and characteristics of radiation emitted or reflected
from the earth's surface, is dependent upon the characteristics
of the objects. Electromagnetic energy passing through the
atmosphere is distorted and scattered, treated as atmospheric
interaction, and the electromagnetic radiation that has
interacted with the atmosphere and the surface of the earth is
recorded by a sensor, such as a radiometer or camera.