561
26.4 Application of RS and GIS
26.4.1 Remote Sensing (RS)
RS is the technique of deriving information about
objects on the surface of the earth without physically coming into contact with them. This process
involves making observations using sensors
(cameras, scanners, radiometer, radar, etc.)
mounted on platforms (aircraft and satellites),
which are at a considerable height from the earth’s
surface and recording the observations on a suitable medium (on photographic fi lms and videotapes or digital data on magnetic tapes). When
EMR falls upon a surface, some amount of its
energy is absorbed, some amount is transmitted
through the surface and the rest is refl ected. It is
these refl ected and emitted radiations which are
recorded on either the photographic fi lm or digital
sensor. Since the intensity and wavelengths of this
radiation are a function of the surface in question,
each surface is described as processing a characteristic ‘spectral signature’. If an instrument can
identify and distinguish between different spectral signatures, then it will be possible to map the
extent of surfaces using RS. Satellite RS is widely
used as a tool in many parts of the world for the
management of the resources and activities.
26.4.1.1 RS Data
The wetlands are mapped often by using IRS P6
LISS III data. They provide data in 4 spectral
bands: green, red, near-infrared (NIR) and shortwave infrared (SWIR), with 23.5-m spatial resolution and 24-day repeat cycle. The spatial
resolution is suitable for 1:50,000 scale mapping.
The state of Assam, for example, is covered in 17
IRS LISS III scene.
26.4.1.2 Ground Truth Data
Some amount of fi eld observations, called
‘ground truth’, are required in RS techniques in
order to convert into meaningful information.
Such work involves visiting a number of test
sites, usually taking the satellite images. The
location of the features is recorded using the
GPS. As per the NWIA manual, the standard pro
forma is generally used to record the fi eld data.
Field photographs are also usually taken to record
the water quality (subjective), status of aquatic
vegetation and water spread.
26.4.1.3 Other Data
Standard Survey of India (SOI) topographical
maps are generally used for reference purpose.
Lineage data of National Wetland Maps at
1:250,000 scale are used for reference.
26.4.1.4 Satellites and Sensors
The mode can be geostationary, permitting continuous sensing of a portion of the earth or sun‐synchronous with polar orbit covering the entire earth
at the same equator crossing time. The Landsat
series of satellites have a repeat period ranging from
16 to 18 days, whereas in the case of IRS, it is 22
days. Satellites cover the same area and provide
continuous coverage of a fi xed area. The sun‐synchronous satellites have a synoptic coverage. The
ground area covered by the satellite’s passes can be
obtained by referring to its path and row. Sensors
are devices used for making observations. They
consist of mechanisms, usually sophisticated lenses
with fi lter coatings, to focus the area observed onto
a plane in which detectors are placed. These detectors are sensitive to a particular region in which the
sensor is designed to operate and produce outputs,
which are either representative of the observed area,
as in the case of the camera; or produce electrical
signals proportionate to radiation intensity.
26.4.2 Geographical Information
Systems (GIS)
A GIS is a system of software and procedures to
facilitate the management, manipulation, analysis,
modeling, representation and display of geo‐referenced data to solve complex problems regarding
planning and management of resources.
A function of an information system is to
improve one’s ability to make decisions. An
26.4 Application of RS and GIS
26.4 Application of RS and GIS
26.4.1 Remote Sensing (RS)
RS is the technique of deriving information about
objects on the surface of the earth without physically coming into contact with them. This process
involves making observations using sensors
(cameras, scanners, radiometer, radar, etc.)
mounted on platforms (aircraft and satellites),
which are at a considerable height from the earth’s
surface and recording the observations on a suitable medium (on photographic fi lms and videotapes or digital data on magnetic tapes). When
EMR falls upon a surface, some amount of its
energy is absorbed, some amount is transmitted
through the surface and the rest is refl ected. It is
these refl ected and emitted radiations which are
recorded on either the photographic fi lm or digital
sensor. Since the intensity and wavelengths of this
radiation are a function of the surface in question,
each surface is described as processing a characteristic ‘spectral signature’. If an instrument can
identify and distinguish between different spectral signatures, then it will be possible to map the
extent of surfaces using RS. Satellite RS is widely
used as a tool in many parts of the world for the
management of the resources and activities.
26.4.1.1 RS Data
The wetlands are mapped often by using IRS P6
LISS III data. They provide data in 4 spectral
bands: green, red, near-infrared (NIR) and shortwave infrared (SWIR), with 23.5-m spatial resolution and 24-day repeat cycle. The spatial
resolution is suitable for 1:50,000 scale mapping.
The state of Assam, for example, is covered in 17
IRS LISS III scene.
26.4.1.2 Ground Truth Data
Some amount of fi eld observations, called
‘ground truth’, are required in RS techniques in
order to convert into meaningful information.
Such work involves visiting a number of test
sites, usually taking the satellite images. The
location of the features is recorded using the
GPS. As per the NWIA manual, the standard pro
forma is generally used to record the fi eld data.
Field photographs are also usually taken to record
the water quality (subjective), status of aquatic
vegetation and water spread.
26.4.1.3 Other Data
Standard Survey of India (SOI) topographical
maps are generally used for reference purpose.
Lineage data of National Wetland Maps at
1:250,000 scale are used for reference.
26.4.1.4 Satellites and Sensors
The mode can be geostationary, permitting continuous sensing of a portion of the earth or sun‐synchronous with polar orbit covering the entire earth
at the same equator crossing time. The Landsat
series of satellites have a repeat period ranging from
16 to 18 days, whereas in the case of IRS, it is 22
days. Satellites cover the same area and provide
continuous coverage of a fi xed area. The sun‐synchronous satellites have a synoptic coverage. The
ground area covered by the satellite’s passes can be
obtained by referring to its path and row. Sensors
are devices used for making observations. They
consist of mechanisms, usually sophisticated lenses
with fi lter coatings, to focus the area observed onto
a plane in which detectors are placed. These detectors are sensitive to a particular region in which the
sensor is designed to operate and produce outputs,
which are either representative of the observed area,
as in the case of the camera; or produce electrical
signals proportionate to radiation intensity.
26.4.2 Geographical Information
Systems (GIS)
A GIS is a system of software and procedures to
facilitate the management, manipulation, analysis,
modeling, representation and display of geo‐referenced data to solve complex problems regarding
planning and management of resources.
A function of an information system is to
improve one’s ability to make decisions. An
26.4 Application of RS and GIS