If the term is broken down into syllables, then you can get two words– first one is ‘remote’ which means ‘distance’ (here distant object or phenomenon), and the second one is ‘sensing’ that means to sense or acquisition of information. Hence, by analyzing the above definitions it can be said that, the term ‘Remote Sensing’ refers to the acquisition of information about an distant object or phenomenon without coming into physical contact with the object. It refers to satellite based sensing technology that helps to analyse and interpret as well as to gather information about concerned object or phenomenon.


Basic principles of remote sensing

Remote sensing always follows some basic principles that consequence to the completion of the process. Eight such principles can be mentioned.

1. Energy source

There must be a source of energy. Basically sun is the major natural source of energy that illuminates the object of interest. But this energy or electromagnetic radiation can also be generated artificially through flashguns or other devices.

2. Transmission of radiation from source to object surface

The radiating energy from the source, whether it is natural or artificial, transmits to the surface of the object (e.g., Earth surface). This energy is the electromagnetic radiation or EMR, that varies in its wavelengths. There are called Electromagnetic Spectrum, each of which has its own characteristics and application.

3. Reciprocal interaction between radiation and object

After the radiation transmits to the object surface from its source, then the reciprocal interaction occurs between them. As each object varies in its structural elements, thenceforth each object reacts differently to the interaction of electromagnetic radiation. As a consequence, the EMR might be absorbed, or reflected, or transmitted by the objects. For instance, if we consider the visible portion of the electromagnetic spectrum, then it is seen that feculent water body reflects the green (G) and blue (B) region of the visible spectrum than that of any fresh water body.


4. Backscattering of radiation from object

The reflected radiation from the object surface then backscatters towards the satellite sensor, through the Earth's atmosphere. But it is important to mention that, sometimes the reflected radiation might be scattered due to the presence of atmospheric constituents, such as dust, water and gaseous molecules etc.


5. Capturing of the propagated radiation by satellite sensor

The most important component of remote sensing is the satellite sensor. That sensors which are placed into the satellites, detect and record the reflected or emitted energy (in the form of electromagnetic radiation) from the objects of the Earth surface. These satellites are placed in Polar Sun-synchronous, or Geostationary, or Geo-synchronous orbits around the Earth.

6. Transformation of the recorded radiation into digital datasets

The onboard sensors then transform the recorded radiation into the digital form of datasets. These are the images that consists of different digital numbers. Thereafter the converted digital datasets propagate to the ground based receiving station on the Earth surface by the satellite sensors.

7. Eduction of informations from datasets

After all these are done, the electronic datasets are then processed to extract the digital imagery. Then all the errors are eliminated, and finally the eduction of informations is performed by applying digital image processing techniques, or visual interpretation method.

8. Application of the information in mapping and other purposes

Lastly all the collected informations are applied in mapping of the considered object, or sometimes qualitative or quantitative measures are taken into account to study any particular phenomena, or to solve any problem, or in many other purposes.

Thus a complete remote sensing process follows all of the aforementioned principles in proper way, and helps us to explore or to study any objects or phenomenons on the Earth surface.

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