Literature Review
“Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with object, area or phenomenon under investigation”(Lillesand and Kiefer, 2000). Even in our daily life when we see/hear/read something, we are using the principles of remote sensing. But here we are to deal with only electromagnetic energy sensors that are operated from airborne and space borne platforms to assist in inventorying, mapping and monitoring earth resources. Remote sensing involves two major tasks. These are data acquisition and data analysis. The main elements of data acquisition process are:
- energy sources and its propagation through atmosphere, and
- energy interactions with the earth surfaces and features.
Sensors usually record variations in the way earth surface features reflect or emit electromagnetic energy.
Based on how the sensors and electromagnetic energy interact with earth surface features, remote sensing systems are broadly classified in to two categories:
- passive remote sensing system; and
- active remote sensing system (Swain and Davis, 1978).
Passive remote sensing systems record the reflected electromagnetic energy from the features. Here, incident energy is always natural and never from the sensor itself. These sensors use optical part of the electromagnetic spectrum, which extends from approximately 0.3 to 14 μm.