Page 17 - RemoteSnsing&GIS by PK Gogoi

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n the above diagram, it has depicted about the of EMR differs. Similarly, within the visible on a camera at dark night can be an example of

Irate of reflection/emission of terrestrial range, such reflectance is low in clean water but active remote sensing. However in active remote
bodies like Water , Soil/Sand, Vegetation to it is different in case of water bodies when sensing, satellite emits raditation towards target

back to the atmosphere and, relationship mixed with sand particles ,mud etc. After and the sensor detects and acquire information
between predominance of wavelengths zone of getting an idea of ‘amount of reflectance ‘ in by obtaining reflected rediation from the

EMR and its rate of reflectance. Obviously, the different wavelength regions of EMR spectrum, target.e.g LIDAR,RADAR,SONAR
reflectance rate of objects from the earth differ now we can able to understand as to why in

greatly in different sections of spectral bands, remote sensing,such wavelengths are used
e.g. the reflectance of clean water is low differently.

meaning all bands of EMR is absorbed and very ASSIVE Vs ACTIVE REMOTE
little amount of reflection is there in the visible PSENSING

section of the EMR. At the same time, whenever
emote Sensing process is always
we see that reflectance of green vegetation is
associated with source of illumination
highest in the NIR region of a spectrum. It
Rin the form of light energy. On the
should be bare in mind that for better
basis of the acquired energy of light directly or
understanding of geographical resources over
indirectly from a source , the remote sensing is
the earth surface, the reflectance bands of
of two distinct types - Passive Remote Sensing
spectrum plays a pivotal rule. The NIR (Near
and Active Remote Sensing. The former one
Infra red ) is taken into considered for a better
,i.e, Passive Remote Sensing is one where the
analysis of vegetative cover on the earth’s
Sun is the source of illumination and the Earth
receives light in the form of EMR .It is called
Passive Remote Sensing as because in this

process source of light is from other source . The

reflected and emitted solar energy from the earth
is received by the Sensors of a remote sensing ,
and digital information are acquired. In this type

of remote sensing process ,Sensors are sensitive

to photo electric energy or sun light in the form
of its EMR. Contrary to that ,in Active Remote
here are three major segments/components .4.1. Remote Sensing Platforms :
Sensing the light or illuminated energy is
Tof Remote sensing - 2Platforms- A platform is the vehicle or
urface as because vegetation has high generated by the instrument itself. In this remote
sreflectance within NIR and MIR section of sensing process ,illuminated energy is generated 1 .Platforms carrier for remote sensing . Platform is a Stage

EMR.Furthermore , such reflection differs from by the satellite itself.As this system is active day Sensors where sensor or camera is mounted to acquire
object to object depending upon the capacity of and night without depending upon other source 2 Orbits information about a target under investigation.

absorption. To understand the fact that from of illumination, therefore it is called active 3 According to Lillesand and Kiefer (2000), a
species to species of vegetation ,the reflectance remote sensing. By taking a photo using ‘flash’ platform is a vehicle, from which a sensor can