Radar Remote Sensing By Falah Fakhri Post-doctoral Scholar falah.fakhri@utu.fi

Radar Remote Sensing

By

Falah Fakhri

Post-doctoral Scholar

falah.fakhri@utu.fi

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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