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Synthetic Aperture Radar (SAR)
National Disaster Management Institute Ministry of Security and Public Administration
RADAR
• RAdio Detection And Ranging
RADAR • An object-detection system that uses radio waves to determine the range,
altitude, direction, or speed of objects
• It was developed by several nations before and during World War 2. The
term RADAR itself was coined in 1940 by the United Navy
Wavelength
Passive vs. Active Satellite • Passive satellite
- reflect the incident electromagnetic radiation without any modification or
amplification
- It can not generate power they simply reflect the incident power
- Optical satellites (Kompsat-2,3, Landsat, MODIS…)
- Observation time: after sunrise until sunset
- high spatial resolution
• Active satellite
- Satellites which can transmit power
- They can amplify or modify the incident signal for transmission
- SAR satellites (Kompsat-5, ALOS-1, ENVISAT, TerraSAR-X)
- Unlimited observation time
- low spatial resolution
- high expense
Synthetic Aperture Radar (SAR) • SAR is a form of radar whose defining characteristic is its use of
relative motion, between an antenna and its target region, to provide
distinctive long-term coherent-signal variations, that are exploited to
obtain finer spatial resolution that is possible with conventional
beam-scanning means
• Frist citizen SAR satellite: SEASAT (1978, US)
• Resolution↑, Antenna length↑, high frequency ↑, short wavelength ↓
• Interferometry, Polarimetry: Phase
• Ragargrammetry: (Intensity)
Real vs. Synthetic
Real vs. Synthetic
TanDEM-X: TerraSAR-X add-on for
Digital Elevation Measurement
200-500m
COSMO-SkyMed : Constellation of small Satellites form the Mediterranean basin Observation
SRTM (Shuttle Radar Topography Mission, JPL, NASA)
60m mast
3 arc second data 90*90m, Global
1 arc second data 30*30, USA
Antenna type
Pi-SAR2 (Airborne)
TerraSAR-L (11m*2.9m)
Radarsat-2 (15m*1.5m)
SAR observation mode
Type of Mode
1. Spotlight
2. Stripmap
3. Scansar
SAR principle
Side-looking system Difference between SAR and Optical imagery
Radar reflection pattern
SAR distortion
Interferometry SAR imagery is recoded the pixel information by complex value
Optical imagery is recoded the reflected power from ground object
Complex
Number
intensity
phase
Radar reflection from Object
Distance between senor and object
Interferometry
noiatmdefotopoflat
is the interferometric phase
flat is the flat earth phase
topo is the topographic phase
defo is the deformation phase
atm is the atmospheric delay phase
noi is the noise.
Interferometric SAR
Interferometry
InSAR (IfSAR) : Interferometric Synthetic Aperture Radar
DInSAR : Differential Interferometric Synthetic Aperture Radar
PSI (PSInSAR) : Persistent Scatterer Interferometric SAR
SqeeSAR
SBSA (Small baseline)
PolSAR : Polarimetric SAR
noiatmdefotopoflat
Different reflection due to wavelength
Signal reflection
Smooth
Specular
Intermediate
Specular and Diffuse
Rough
Diffuse
DEM generated by different band
L-band elevation model X-band elevation model
Polarimetry
Polarimetric AIRSAR
San francisco, USA
PSI (PSInSAR)
Sydney, Australia
Ground subsidence at
underground mining area
2011-01-11
CSK image, Brisbane, Queensland,
Australia
2011-01-12
CSK image, Brisbane, Queensland,
Australia
Flooding at Queensland, Australia Intensity image analysis
Coherence analysis and Vegetation analysis
Flood at Queensland, Australia
CSK, Rockhampton, Queensland, Australia
BBC international internet.
Flood at Queensland, Australia
Flood Queensland, AU
2011-01-04 2010-12-14
MODIS Aqua imagery
Flood in Germany
2013-06-06 2013-05-05
MODIS Terra imagery
Flood map in Germany (Optical image)
Flood map in Czech Republic (RADARSAT-2)
Earthquake detection
Sichuan Earthquake, China, 2008
Christchurch Earthquake, NZ,2011
SAR Intensity image analysis
China earthquake
Barrier lake due to earthquake
DEM generation
Oil spill disaster
ERS-1 data ENVISAT data
X-,C-band (3, 5cm)
Oil spill disaster in Korea, 2007
ENVISAT ASAR, ESA
2007-12-11
PSI result in Busan
Bushfire monitoring (Multispectral image)