radar remote sensing by falah fakhri post-doctoral scholar [email protected]
TRANSCRIPT
Radar Remote Sensing
By
Falah Fakhri
Post-doctoral Scholar
https://www.researchgate.net/profile/Falah_Fakhri
https://falahfakhri.wordpress.com
https://twitter.com/FALAHFAKHRI
Department of Geography and Geology
MAANTIETEEN JA GEOLOGIAN LAITOSTuesday 26/08/2014 Time: 14:00 – 15:00
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Seminar’s outline
• Passive and active Remote Sensing
• Concept of Radar
• Concept of SAR
• Optical Image Format and Characteristics
• SAR Image Format and Characteristics Amplitude Phase
• Images acquisitions
• Software's are used in SAR (Radar Images Processing)
Passive and active Remote Sensing 1/1 Passive vs. Active Sensors
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Concept of Radar (1/10)
Echolocation
is the use of
sound waves and
echoes to determine
where objects are in space. Bats use echolocation to navigate and find food in the dark.
To echolocate, bats send out sound waves from their mouth or nose. When the sound waves hit an object they produce echoes. The echo bounces off the object and returns to the bats ears. Bats listen to the echoes to figure out where the object is, how big it is, and its shape.
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Concept of Radar (2/10)
Imagine you are in the Grand Valley and you shout. The cliffs
will reflect the sound wave. After some time you will hear an
echo, which is not exactly the same compared to what you
shouted. This is the “principle” of a radar!
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Concept of Radar (3/10)
RADAR stands for Radio Detection and Ranging … so what is
a Radar?
A: (Imaging) Radar is an active system that uses a transmitter
to illuminate a scene. The pulses sent are microwaves, i.e. a
wave with an amplitude and a phase, having a certain frequency
and polarization.
The radar then records the echo or
(backscatters)
scattered back from the objects/targets
B: Non imaging
Concept of Radar (4/10)
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Concept of Radar (5/10)
radars illuminate the target
so that they
• can operate day and night.
• Microwave frequencies
Electromagnetic
waves penetrate to
Some extent through media.
• At most frequencies clouds are
transparent!
• Complex interaction with medium or
target:
a “Radar image” is not a photo!
Concept of Radar (6/10)
Passive Remote sensing Active Remote Sensing
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Concept of Radar (7/10)
interaction with medium or targets
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The transmitted pulse interacts with the Earth surface and only a portion of it is backscattered to the receiving antenna
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Concept of Radar (8/10)
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Concept of Radar (9/10)
• Surface Roughness:
Back-scattering increases with roughness
• Moisture content :
Back-scatteringincreases with moisture
• Topography :
Viewing geometry affects the signal
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Concept of Radar (10/10)
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Concept of SAR (1/1) Synthetic Aperture Radar (SAR)
• It has cloud-penetrating capabilities
because it uses imaging system (Microwave frequencies
Electromagnetic) waves.
•It has day and night and weather-independent
operational capabilities because it is an active system.
•Finally, its ‘interferometric configuration’
Optical Image Format and Characteristics (1/1)
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Characteristics of Image
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SAR Image Format and Characteristics (1/6)
Detected SAR image,Single Look Complex, (SLC)
Raw data
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SAR Image Format and Characteristics (2/6)
Amplitude
The detected SAR image contains
a measurement of the Amplitude
(Intensity) of the radiation
backscattered toward the radar by
the objects (scatterers) contained in each SAR resolution
cell.
Typically, exposed rocks and urban areas show strong
amplitude ( bright pixel) whereas smooth flat surface, like quiet water basins show low amplitude (dark pixels) since the
Backscatters (radiation) is mainly measured away from the radar.
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SAR Image Format and Characteristics (3/6)
Phase
The pulses (radiation) transmitted
from the radar has to reach the
scatterers on the ground and then
to comeback to the radar in order
to form the SAR image.
Scatterers at different distance from the radar introduce a different delay between transmission and reception of the radiation.
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SAR Image Format and Characteristics (4/6)
Ascending
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SAR Image Format and Characteristics (5/6)
Descending
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SAR Image Format and Characteristics (6/6)
Satellite Radar Systems available now and into the future
Software's are used in SAR (Radar Images Processing) (1/6)
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https://earth.esa.int/web/guest/home
Software's are used in SAR (Radar Images Processing) (2/6)
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https://earth.esa.int/web/guest/home
Software's are used in SAR (Radar Images Processing) (3/6)
NEST (NEW ESA SATELLITE TOOL BOX)
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Software's are used in SAR (Radar Images Processing)(4/6)
NEST (NEW ESA SATELLITE TOOL BOX)
Software's are used in SAR (Radar Images Processing)(5/6)
NEST (NEW ESA SATELLITE TOOL BOX)
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Software's are used in SAR (Radar Images Processing)(6/6)
GAMMA Remote sensing
Software's are used in SAR (Radar Images Processing)(6/6) ERDAS, 2014
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