3_sar application in geology.pdf3_sar application in geology

7/26/2019 3_SAR Application in Geology.pdf3_SAR Application in Geology

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RADARSAT-1

& 2

SAR-

advantage &

Disadvantage

SAR APPLICATION IN

GEOLOGY


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Geological structure mapping

Lineament mapping

Geomorphological mapping

Surficial material assessment

Surficial bedrock mapping

Sedimentology mapping

Landslide hazard assessment

USEFUL IN .


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RADARSAT 1

Radarsat-1 launched in 1995

operates in C-band

synthetic aperture radar (SAR)

operates in 7 beam position modes

able to steer it beams from 10 to 60

incidence angle

resolution from 8 to 100m


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RADARSAT-1

Beam Mode Position

incidence angle)

Resolution m) Area km)

Fine 15 8 50 x 50

Standard 7 25 100 x 100

Wide 4 30 165 x 165

Extended High 6 25 75 x 75

Extended Low 1 35 170 x 170

ScanSAR Narrow 2 50 300 x 300

ScanSar Wide 1 100 500 x 500

Radarsat International. n.d. Radarsat Geology Handbook


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RADARSAT-1


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RADARSAT-1

Standard mode ScanSAR Wide


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LITHOLOGY AND STRUCTURE

The finer siltstone particles produce a darker return, while the coarser

limestone particles produce a brighter backscatter return attributed

to the increased surface roughness (Standard beam).


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GEOMORPHOLOGICAL/LANDFORM/

STRUCTURE MAPPING

The Treetop Geology concept is

illustrated in this RADARSAT image

of a dense tropical forest. An eroded,

sedimentary dome structure is

clearly evident (Fine beam)


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LANDSLIDE HAZARD ASSESSMENT


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CONDITIONS INFLUENCING GEOLOGICAL

MAPPING

Geological

activity

Radar response Beam mode Incidence angle

Geological

structure mapping

topographic relief fine and standard for

detailed mapping

Wide and ScanSAR forbasin wide mapping

shallow angle by

enhancing

topography shadowIntermediate angle

for high relief terrain

Lineament topographic relief fine and standard for

detailed identification

Wide and ScanSAR for

regional identification

shallow angle to

enhance topographic

relief

Geomorphological/

landform

topographic relief fine and standard for




shallow angle to

enhance subtle

terrain through

shadowing


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MAPPING

Geological

activity

Radar response Beam mode Incidence angle

Surficial material

assessment

unique

backscatter in

response to

different soilroughness & soil

moisture

fine and standard for




soil moisture (steep

angle)

soil roughness

(shallow angle)

Surficial bedrock

mapping

unique

backscatter due

to fracture pattern

in different rocks,rock fabric,

texture and

mineral

composition




regional identification Better with low moisture

level (backscatter

correlated closely with

surface rougness)

shallow angle to

maximize the contrast

in backscatter

resulting in varyingsurface roughness


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MAPPING

Geological activity Radar response Beam mode Incidence angle

Sedimentology

mapping

unique

backscatter in

response to

different soil

roughness & soilmoisture

Topographic relief

Erosional pattern





Steep angle (soil

moisture)

Shallow angle (soil

roughness)

Landslide hazard

assessment

Surface roughness

Landslide

deposited area

Change in

vegetation pattern



Shallow angle


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Speckle Filtering

LINEAMENT MAPPING


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Stages in despeckle

LINEAMENT MAPPING (CONT )


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Lineament filter

a) Directional

b) Non-directional



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Lineament

Lineament

Lineament

Important in

Determination of

groundwater source

Landslide

Mineral potential area

Geological structure

studies


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Used for mapping ground changes and infrastructure damages

Calculating the ratio differences in terms of backscatter

intensity based on multitemporal images

The drawback is

significant variability of backscatter that depends on theincidence angle when the image is required. The sensor must

acquire the image at the same incidence angle before the

earthquake happen so that the backscatter intensity can be

quantified.

The concept when assessing damages due to an earthquake

due to side-looking acquisition geometry, urban constructions

often produce distinct signal caused by double bounce

mechnanism, this pattern changes when the buildings are

damaged by an earthquake

EARTHQUAKE STUDIES


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Used for mapping volcanic deformations

Useful in times of eruptions where there is a lot of smoke

obscuring visibility

Technique: calculating a dif ference of intensity images from

before and after the event. For example, lahar and pyroclasticflow

Drawback: certain band (C- & L- bands) are not clearly show

changes of backscatter intensity

VOLCANIC ACTIVITY


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Useful for storm-induce landsliding where cloud cover

impeded the use of optical sensor

However, due to better resolution and capability of multiband

manipulation, optical data is still preferable than SAR

Drawback:

a) layover and shadowing effect in high slopes area.

b) Different viewing position will affect the backscatter

intensity quantification

c) Not much distinct backscatters from the images taken

before and after an event due to the size of landslides and

also if the background is the same with the landslides (bare

ground)

LANDSLIDES


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Ideal sensor for flood studies due to backscatter signature of

water is so distinct compare to the background

Floodwater remain visible for longer time

Delineation of flood boundary can be done due to flood

receding slowly

Water appear darker in SAR image

SAR able to detect flood under canopy area

However, experience researcher is needed to interpret the

backscatter data under the canopy and image before and

after a flood event are needed for comparison

FLOODING

3_sar application in geology.pdf3_sar application in geology

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