Page 18 - RemoteSnsing&GIS by PK Gogoi

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be operated. For remote sensing applications,
sensors should be mounted on suitable stable
platforms. These platforms can be ground based,
air borne or space borne based.
As the platform height increases the
observational area increases. Thus, higher the
sensor is mounted; larger synoptic view is
obtained. The types or characteristics of
platform depend on the type of sensor being
attached and its necessity of researcher.
Depending on task, platform can vary from
ladder to satellite. Following are the three types
of platform
.4.1.1 Ground based platform
Ground platforms are used to record
2detail information about the surface very
closely. Some example of ground based
platform are
I ground vehicle (Mobile Hydraulic Platform) :
Sensor is fixed at a height of 15 meter above the
ground with a hydraulic platform.
2 tower : At the cell phone tower, sensor is fixed
and aerial data are received.
3 air balloon : Altitude range is 22 to 40 Km. It
is used for collection of data related to
monitor weather phenomenon,
pollution etc Balloons Balloons are
used for remote sensing observation
(aerial photography) and nature
conservation studies. Balloon floats
at a constant height of about 30 km.
t consists of a rigid circular base plate
for supporting the entire sensor system which
is protected by an insulating and shock proof
light casing.
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The height of ground based platform is
from a few meters to 50 Km or in the other
words we can say that the ground based
platforms are found bellow 50 Km from the
Earth surface.
2.4.1.2 Air borne plattform :
irborne platforms are used to atellites are man made objects that revolve
Acollect very detailed images and Saround the earth and sensors installed
features. The collection of data over any portion onboard captures data of the earth's surface
of Earth's surface at any time but it is very covering areas of more than hundreds of square
expensive platform as compared to ground based kilometers. Because of their orbits, satellites
platforms .There are some examples of airborne permit repetitive coverage of the earth's surface
platform on a continuing basis. There are two types of
.Drones /UAV : Drone is a miniature well recognized satellite platforms: which are
1remotely piloted aircraft. It is designed to ‘Manned Satellite Platforms’ like Space
fulfill requirements for a low cost platform, with Shuttles, Space crafts, International Space
long endurance, moderate payload capacity and Stations etc. and ‘Unmanned Satellite Platforms’
capability to operate without a runway or small like Landsat series, SPOT series and IRS series
runway. Drone includes equipment of of remote sensing satellite NOAA series of
photography, infrared detection, radar meteorological satellites, the entire constellation
observation and TV surveillance. It uses of the GPS satellites and the GOES and INSAT
satellite communication link. An onboard series of geostationary environmental are
computer controls the payload and stores data examples of unmanned satellite category.
from different sensors and instruments. .4.1.3.a Space Borne Platforms (On the
2basis of orbital height )
. Rockets as Platforms : Prior to use of
2airplanes, aerial photographs were obtained n highlighting the satellite sensors placed at
by rocketing a camera nto the sky and then Idifferent heights ,especially in space ,and
retrieving the camera and film. The high altitude used for satellite remote sensing for acquiring
sounding rocket is fired from a mobile launcher. optical image , it is to be mentioned that on the
During the flight it takes snapshot from above
the earth and decend down in a capsule.
. Aeroplane : High spatial resolution 20 cm
3or less can be obtained by sensors from the
aircraft. Analog photography is possible. It is
cost effective and nedds continues fly.
.4.1.3 Space Borne Platforms : Space
2borne remote sensing is carried out from the
outer space or at an altitude higher than the
earth's atmosphere and utilizes space shuttle or
more commonly satellites as platforms.. Space-
borne imaging ranges from altitude 250 km to
36000 km.