Synthetic Aperture Radar for Rapid Flood Extent...
Transcript of Synthetic Aperture Radar for Rapid Flood Extent...
National Aeronautics and Space Administration
www.nasa.gov
ARSET Applied Remote Sensing Training http://arset.gsfc.nasa.gov @NASAARSET
Synthetic Aperture Radar for Rapid Flood Extent Mapping
Sang-Ho Yun
ARIA Team Jet Propulsion Laboratory California Institute of Technology
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Atmospheric Windows & Current SAR Missions
TerraSAR-X COSMO-SkyMed Radarsat-2 Sentinel-1A ALOS-2
X-band (3 cm)
C-band (6 cm)
L-band (24 cm)
S-band (12 cm)
γ-rays, x-rays infrared microwave
visible
KOMPSAT-5
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Earth is Mostly Cloudy
Average cloudiness over Earth in April 2015 seen from Aqua Satellite. At any given time, around 70% of the Earth is covered by clouds.
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And Half Dark
At any given time, 50% of the earth is dark.
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Radiation Pattern
θx
θy
Antenna
Radiation pattern
U
x
y
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Some Imaging Radar Jargon SAR antenna
-3dB
footprint
swath look angle
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Real Aperture Radar Synthetic Aperture Radar
…
Synthetic Aperture Radar (SAR)
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Real Aperture Radar
Synthetic Aperture Radar
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Synthetic Aperture Radar (SAR)
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SAR image (amplitude)
SAR processing
Raw data (complex)
Amplitude Phase
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Microwave Scattering (Smooth)
h < λ/2 Dark
λ
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Bright
Microwave Scattering (Rough)
h < λ/2
λ
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Darker
Floods Form Smooth Surface
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Brighter
Floods with Tall Vegetation
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Brighter
Floods with Artificial Structure
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SAR Image (Before)
©ALOS-2 Operation and Data Distribution Consortium, Original Data
provided by JAXA
ALOS-2 2015-09-30
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SAR Image (After)
©ALOS-2 Operation and Data Distribution Consortium, Original Data
provided by JAXA
ALOS-2 2016-01-06
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Flood Extent Maps
• DerivedfromALOS-2SARData• 2016-01-06datacomparedto2015-09-30
• ProcessingLevel:1.5• Coverage:70kmx240km• ResoluIon:~12m• AreaofpotenIalfloods:Blue+Red
• Bluepolygons:Floodswithsmoothsurface
• Redpolygons:FloodswithtallvegetaIon OriginaldataprovidedbyJAXA
• Productformats• KMZ(Polygons)• KMZ(PNGimage)• GeoTiff• Shapefile
• Availabletodownloadath_p://aria-share.jpl.nasa.gov/events/20160111-US_Midwest_Floods/
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Google Earth NASA Flood Map
Flood Extent Map
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JAXA Flood Map NASA Flood Map
Flood Extent Map
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SAR Data Acquisition Latency
1993 1998 2004 2009 2015 20200
1
2
3
4
5
6
7
8
TerraSAR−X (X/11)TanDEM−X (X/11)
PAZ (X/11)TerraSAR−X Next Gen. (X/11)
HRWS (X/11)KOMPSAT−5 (X/28)
KOMPSAT−6 (X/28)COSMO−SkyMed 1 (X/16)
COSMO−SkyMed 2 (X/16)COSMO−SkyMed 3 (X/16)
COSMO−SkyMed 4 (X/16)COSMO−SkyMed Sec. Gen. 1 (X/16)
COSMO−SkyMed Sec. Gen. 2 (X/16)ERS−1 (C/35)
ERS−2 (C/35)Envisat (C/35)
Envisat−ext (C/30)Sentinel−1A (C/12)
Sentinel−1B (C/12)Sentinel−1C (C/12)
Sentinel−1D (C/12)RADARSAT−1 (C/24)
RADARSAT−2 (C/24)RADARSAT Constellation 1 (C/12)RADARSAT Constellation 2 (C/12)RADARSAT Constellation 3 (C/12)
NISAR (LS/12)ALOS−1 (L/46)
ALOS−2 (L/14)ALOS−3 (L/14)
SAOCOM−1A (L/16)SAOCOM−1B (L/16)
Tandem−L 1 (L/8)Tandem−L 2 (L/8)
Year
Day
s
L - band C - bandX - bandS - band
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Summary
• Radar sensors see through clouds day and night.
• Synthetic Aperture Radar achieves high resolution (3 – 20 m) over a wide swath (50 – 250 km).
• SAR amplitude is sensitive to floods, with pixel values becoming either darker or brighter.
• Achievable SAR data acquisition latency is already less than a day
Copyright 2016 California Institute of Technology. Government sponsorship acknowledged.
Copyright 2016 California Institute of Technology. Government sponsorship acknowledged.