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
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