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)