Definitions of Remote Sensing

Geographical techniques involve numerous aspects in it, and among these, one of the most important technique is Remote Sensing. The definitions of Remote Sensing are as under.

Eminent scholars Ralph W. Kiefer and Thomas M. Lillesand defined remote sensing as
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 the object, area or phenomenon under investigation.


India's National Remote Sensing Agency, which is now renamed as National Remote Sensing Centre or NRSC gave the definition (in 1995) of remote sensing as follows
Remote sensing is the technique of deriving information about objects on the surface of the earth without physically coming into contact with them.

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 art of science to acquire information about any distant object or any phenomenon without establishing physical contact with it.

In geographical context, remote sensing denotes the use of man-made satellites or various spacecrafts to study various objects of the Earth, whether on the Earth's surface or atmosphere, depending on the propagation of electromagnetic radiation.

Basic Concept of Remote Sensing

Electromagnetic radiation or EMR is a key component in the process of remote sensing. Remote sensing works depending on about four types of radiating features of EMR– absorption, transmission, reflection, and emission. While electromagnetic radiation falls upon any object surface, it might be absorbed by the object or transmitted, reflected, or sometimes the object emit might radiation from itself (such as in the form of heat).

Satellites or spacecrafts always consists of various sensors which, therefore, capture and record that emitted or reflected radiation. But the wavelengths of EMR always vary based on the nature of distant objects, and thus creates different spectral signatures.

Remote sensing sensors play important roles to identify these spectral signatures. The recorded radiation (or datasets) are then used to analyse the object (e.g., features of Earth’s surface) and for mapping purposes.

The Components of Remote Sensing


Remote sensing is a process which involves a certain number of components in it. Therefore total four components can be included in it which collectively develops the framework of remote sensing. These four major components of remote sensing are mentioned below.

1. Source of energy and Object or Phenomenon

Remote sensing process always needs a source of energy to illuminate the considered object through electromagnetic radiation.


2. Electromagnetic Radiation and Atmosphere

As it is mentioned before that the electromagnetic radiation or EMR is the key component of remote sensing process. This radiation illuminates the object of interest passing through the atmosphere, and one more time the radiation interacts with atmosphere while coming back to the remote sensing satellite sensor.

3. Sensor or Satellite Sensor

Remote sensing satellite sensors play a significant role in this process. A sensor is the necessary component in remote sensing. It detects or captures the electromagnetic radiation which reflects or emits from the distant object. After recording the radiation or data, sensor then transmit it to the ground or receiving station.

4. Ground based receiving station

From the satellite sensors, the data (in electronic form) are received and then processed to develop imagery. The imagery then analyzed and interpreted to extract information about that object under investigation. Thus the utmost component of the remote sensing process is completed through the application of the analyzed imagery in proper way, whether by finding the new informations or solving problems.

Thus the basic framework of remote sensing develops based on the aforementioned components.

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