REMOTE SENSING

Remote sensing can be defined as science and art of collecting information regarding objects, area or phenomenon without having physical contact with it. Commonly, Photographs and Eye sight are instance of remote sensing in which from electricity sunlight or artificial light energy is made to strike the object. Light energy which is consists of electromagnetic waves of all length and intensity. When electromagnetic wave falls on the object, it can partly divided

1. absorbed           

2. scattered

3. transmitted      

4. reflected.

Different objects are having different properties of scattering, absorbing, reflecting and transmitting the energy. It is possible to identify the objects by capturing reflected waves with sensors. However this remote sensing has its own restriction in terms of distance and coverage of area at a time. Photographic surveys, in which photographs taken from aircrafts are utilized for making map, fall under this category of remote sensing. This basic remote sensing technique is extended to identifying and quantifying various objects on the earth by using electronic equipments, by observing them from longer distances from the space. Geostationary satellites are launched in the space, for this purpose, which rotate around the earth at the same speed as earth. Therefore the relative velocity is zero and they appear stationary when observed on the earth from any point. The electromagnetic waves sent from the satellite reflected energy is different depending upon the property of the object. The reflected waves by sensors mounted on satellite in the bandwidth of thermal infrared, infrared and micro waves are picked up.

Since each feature on the earth has different reflection property, it is possible with satellite pictures to recognize the features on the earth. Data obtained from satellites are transferred to ground stations through RADARS where user analyses to determine the type of object and the extent of it. This is known image processing. computers are used for quantifying the objects. India has its own remote sensing satellites such as INSAT series, IRS-series, and PSLV series.