Page 8 - RemoteSnsing&GIS by PK Gogoi

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. Transmission, Reception, and objects in the nature and obviously we see different colours . Just n electromagnetic radiation, two
think for a while and thank God for giving us Sensors of special
5Processing (E) - the energy recorded by Icharacteristics are particularly important for
kinds-Eyes,Nose,Ears
the sensor has to be transmitted, in binary form
Fig 2 : Remote Sensing Process
of digital numbers, usually 0 to 9. These
receiving and processing stations processe the

digital information to pictorial form or in o far we have discussed about the very
image. Sbasic concept and terminology of

I I) Data Analysis Remote Sensing. Every element of remote
sensing process is essential . These elements
. Interpretation and Analysis (F) - The
play a pivotal role in receiving information
6processed image is interpreted, visually
from the earth in order to survey specific area or
and/or digitally or electronically, to extract
field of interest on the subject matter of Fig 2: Radiation of sunlight with
information about the target which was
physical ,topography,soil,climate,hydrology EMR spectra.
illuminated. This procedure is known as image
………etc. Following are the conceptual basis
processing or image classification he EMR consists of wavelength and
of understanding of the remote sensing
. Application (G) - The final element of Tfrequency. The wavelength is the length of
processes.
7the remote sensing process is achieved one wave cycle, which can be measured as the
. Energy Source or Illumination and distance between successive wave crests.
when we apply the information we have been
1Radiation principles (A) : Wavelength is usually represented by the Greek
able to extract from the imagery about the
Electromagnetic Radiation(EMR). First and letter lambda (λ). Wavelength is measured in
target in order to better understand it, reveal
foremost,there has to be radiant energy source meters (m) or some factor of meters such as
some new information, or assist in solving a
for remote sensing to illuminate the target . In a nanometres (nm, 10-9_meters), micrometers
particular problem. In the figure, it has depicted
Passive Remote Sensing, the source is the Sun (µm, 10-6 meters) or centimeters (cm, 10-2
the process of Remote sensing in which
and have its light energy radiating from the Sun meters). Frequency refers to the number of
information of the earth is received by sensors
to the Earth in the form of shortwave solar cycles of a wave passing a fixed point per unit
following a sequential and detailed procedure.
radiation. This shortwave incoming solar of time. Frequency is normally measured in
n the next chapter a detailed explanation of
energy is in the form of electromagnetic hertz (Hz), equivalent to one cycle per second,
Ithese essential processes one by one will
radiation. All electromagnetic radiation is a and various multiples of hertz. In the wave
definitely help us to understand the subject in a
combination of electric wave, symbolised as theory it denotes c= fλ , where c = speed of light
lucid manner .
the word ‘E’ and magnetic waves as ‘M’. (3x 10-8 mt/sec) ; f (nu)= number of waves in
Following the basic rule of wave theory, both unit time ,usually expresses in Hz(hertz) ; λ
Remote Sensing is a process of getting information without
the waves bisects each wave at right angles and (lamda) is wavelength(nm).It is now apparent
any direct contact with any object or things. Viewing anything over
the earth by us is an example of remote sensing because the travels(propagates)forward at the speed of that wavelength of radiation is inversely
beautiful nature being looked at by us through our eyes is nothing light(c).The diagrammatic view of the proportional to the frequency, meaning lower
but the reflection of light from objects. Whenever we see some
electromagnetic wave is shown in the figure to the wavelength, higher will be the frequency
colour (say, white) it means all part of visible rays consisting of
seven colours is reflected ,hence nothing is absorbed by the object understand better. It is denoted as EMR for and( molecular) energy and vice versa. As has
and we can see it white. Similarly, within the visible range of colour, Electromagnetic Radiation. been mentioned that earth’s resources always
there are different shades of colour being reflected by the different
Image/Diagram courtesy : Google image search engine