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강원대학교 자원개발연구소 세미나 – 2004 년 4 월 8 일. S ynthetic ? A perture ? R adar !. Systems and Signal Processing. 이 훈 열 강원대학교 지구물리학과. Synthetic Aperture Radar – Systems and Signal Processing. Radarrr rr rrr r rr r . Radio Detection and Ranging WW II, England. Military use

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s ynthetic a perture r adar

강원대학교 자원개발연구소 세미나 – 2004년 4월 8일

Synthetic?Aperture?Radar!

Systems and Signal Processing

이 훈 열

강원대학교

지구물리학과

radarrr rr rrr r rr r

Synthetic Aperture Radar – Systems and Signal Processing

Radarrr rr rrr r rr r
  • Radio Detection and Ranging
  • WW II, England. Military use
  • measure backscattered amplitude and distance to target
  • High power, sharp pulse -> low power, FM-CW chirp signal
  • Navigation radar
  • Weather radar
  • Ground Penetrating Radar
  • Imaging radar
  • cf) LIDAR (Light detection and Ranging)
imaging radar

Synthetic Aperture Radar – Systems and Signal Processing

Imaging Radar

Different Eyes

microwave, UHF, VHF

surface roughness and dielectric constant

Microwave Ranging

All-weather

Cloud-free

Side-looking

Active System

Day and night imaging

independent of solar illumination

aperture

Synthetic Aperture Radar – Systems and Signal Processing

Aperture

Optics : Diameter of the lens or mirror. The larger the aperture, the more light a telescope collects. Greater detail and image clarity will be apparent as aperture increases.

2.4m Hubble Space Telescope

10m Keck, Hawaii

16.4m VLT (Very Large Telescope), Chile

50m Euro50

100m OWL (OverWhelmingly Large T.)

real aperture vs synthetic aperture

Synthetic Aperture Radar – Systems and Signal Processing

Real Aperture vs. Synthetic Aperture
  • Real Aperture :
  • resolution ~ Rλ/L
  • Synthetic Aperture:
  • resolution ~ L/2
  • Irrespective of R
  • Smaller, better?!
  • - Carl Wiley (1951)
image acquisition

Synthetic Aperture Radar – Systems and Signal Processing

Image Acquisition

ERS–1/2 SAR

L: 10 m, D: 1 m

Altitude: 785 km, sun-synchronous orbit

Ground Velocity: 6.6 km/s

Look Angle: Right 17-23 (20.355 mid-swath)

Slant Range: 845 km (mid-swath) Frequency: C- Band (5.3GHz, 5.6 cm)

Footprint : 100 km x 5 km

Incidence Angle: 19  – 26  (23  mid-swath)

Sampling Rate: 18.96 MHz

Pulse duration: 37.1 s

Range gate: ~ 6000 s

Sampling Duration: ~ 300 s (5616 samples)

Inter-pulse period: ~ 600 s ( upto 10 pulses)

Pulse Repetition Frequency: 1700 Hz

Data Rate: 105 Mb/s (5 bits/sample)

sar systems

Synthetic Aperture Radar – Systems and Signal Processing

SAR Systems

Spaceborne SAR

SEASAT-A (USA, 1978), SIR-A (USA, 1981), SIR-B (USA, 1984), SIR-C/X-SAR (USA, Germany, Italy, 1994), ALMAZ-1 (Russia, 1991-1993), ERS-1(EU, 1991-2000), ERS-2 (EU, 1995-), JERS-1 (Japan, 1992-1998), Radarsat-1 (Canada, 1995-), SRTM (USA/Germany, 2000), ENVISAT (EU, 2002),

RADARSAT-2 (Canada, 2005), PALSAR (Japan, 2004), LightSAR (US)*, TerraSAR (Germany)*, MicroSAR(EU)*

Airborne SAR

TOPSAR (JPL, USA), IFSARE(ERIM/Intermap, USA), DO-SAR(Donier,Germany), E-SAR(DLR, Germany), AeS-1(Aerosensing, Germany), AER-II (FGAN, Germany), C/X-SAR (CCRS, Canada), EMISAR (Denmark), Ramses (ONERA, France), ESR (DERA, UK)

Planetary SAR

Magellan (US, 1990-1994), Titan Radar Mapper (US, 2004), Arecibo Antenna, Goldstone antenna

* Under development

sar system modes

Synthetic Aperture Radar – Systems and Signal Processing

SAR System Modes
  • Target – the Earth or planets
  • Vehicle – stationary, airborne, satellite, or spaceship
  • Mode – monostatic and/or bistatic
  • Carrier frequency – X, C, S, L, and/or P bands
  • Polarisation – HH, VV, VH, HV (single-pol, dual-pol, full-pol)
  • Imaging geometry – strip, scan, spot
  • <examples>
  • SIR-C/X-SAR: space shuttle, mono, L/C/X, full-pol.
  • ERS-1/2, Envisat: Earth satellite, mono, C, VV.
  • SRTM: space shuttle, mono/bistatic, C/X, HH/VV.
  • Arecibo Antenna: planetary, stationary, mono/bi, multi-bands, multi-pol.
  • Magellan, Cassini SAR: Venus and Titan, mono, S, HH.
  • AIRSAR/TOPSAR: airborne, mono/bi, L/C/P, full-pol
envisat

Synthetic Aperture Radar – Systems and Signal Processing

ENVISAT

Launched 2002.2.28

C-band, Multpol, multi-mode

Data : Envisat Announcement of Opportunity

image domain

Synthetic Aperture Radar – Systems and Signal Processing

Image Domain

Range (R)

5616 pixels, 100 km

Azimuth (s)

28,000 lines, 106 km

range compression

Synthetic Aperture Radar – Systems and Signal Processing

Range Compression

Linear Chirp Signal

Chirp autocorrelation Function

Matched Filtering

For ERS-1/2,

Pulse duration (T): 37.1 s

Bandwidth : 15.5 MHz

Half power width of autocorrelation function: 0.065 s

Pulse Compression Ratio: 575 (ERS-1/2)

Ground Range Resolution: 12.5 m

Input

Range FFT

Range Matched Filtering

Range iFFT

range migration

Synthetic Aperture Radar – Systems and Signal Processing

Flight Path

Point Target

Range Migration

Quadratic

(Range Curvature)

Linear

(Range Walk)

Azimuth FFT

range migration compensation

Synthetic Aperture Radar – Systems and Signal Processing

Range Migration Compensation

Range (R)

Azimuth (s)

After Range Walk Compensation

Range Migration

azimuth compression

Synthetic Aperture Radar – Systems and Signal Processing

Azimuth Compression

Synthetic Aperture

Real Aperture

Doppler Shift (Linear Chirp Pulse)

: wavelength

L: Antenna length

For ERS-1/2,

Coherent Integration Time (S): 600 ms (5 km footprint)

Bandwidth: 1260 Hz

Half power width of autocorrelation function: 0.8 ms

Pulse Compression Ratio: 756 (ERS-1/2)

Azimuth Resolution: 5 m

Azimuth footprint width:

5 km (ERS-1/2)

Matched Filtering

Azimuth Matched Filtering

Output

sar focusing point target
SAR Focusing – Point Target

azimuth

range

original

After range compression

After migration

After azimuth compression

slide17

Synthetic Aperture Radar – Systems and Signal Processing

Southeast Cost of Spain

ERS-2 (13km x 13km)

Descending,

Right Looking

rule of thumb in sar images

Synthetic Aperture Radar – Systems and Signal Processing

Rule of Thumb in SAR images
  • Backscattering Coefficient
  • Smooth – Black
  • Rough surface – white
  • Calm water surface – black
  • Water in windy day – white
  • Hills and other large-scale surface variations tend to appear bright on one side and dim on the other.
  • Human-made objects - bright spots (corner reflector)
  • Strong corner reflector- Bright spotty cross (strong sidelobes)
slide23

Synthetic Aperture Radar – Systems and Signal Processing

Ship Wakes over the Bering Sea The Calving of Iceberg A-38

(ERS-1 46 km x 28km)

slide24

Synthetic Aperture Radar – Systems and Signal Processing

대청호 ERS-1/2 SAR

Calm Water

Rough Water

slide25

Synthetic Aperture Radar – Systems and Signal Processing

Ronne Ice Shelf, Antarctica The Calving of Iceberg A-38

(Radarsat ScanSAR 150km x 150km)

sar advanced techniques

Synthetic Aperture Radar – Systems and Signal Processing

SAR Advanced Techniques
  • Radarclinometry: DEM from Shape-from-shading (experimental)
  • Radargrammetry: DEM from stereo SAR image matching (m)
  • InSAR:
    • Interferogram: DEM (cm)
    • Coherence: statistical measurement of temporal and spatial decorrelation (cm)
  • DInSAR: surface displacement, penetration depth (mm).
  • Pol-SAR: Classification, segmentation
  • Pol-InSAR: measurement of scattering structure
  • SAR Tomography: 3D target distribution
insar coherence imagery random change detection
InSAR Coherence Imagery Random Change Detection

InSAR Coherence Image

Optical Image

sar applications for peace

Synthetic Aperture Radar – Systems and Signal Processing

SAR Applications for Peace
  • reconnaissance, survelliance and targetting
  • target detection and recognition
  • moving target detection
  • navigation and guidence

- Sandia National Lab. 4-inch SAR

sar peaceful applications

Synthetic Aperture Radar – Systems and Signal Processing

SAR Peaceful Applications
  • Cartography – DEM, DTM
  • Geology – Geological Mapping
  • Seismology – Co-seismic displacement field
  • Volcanology – Prediction of volcano eruption
  • Forestry – Forest classification, deforest monitoring
  • Soil Science – Soil moisture
  • Glaciology – Glacier motion
  • Oceanography – Ocean wave, wind, circulation, bathymetry
  • Agriculture – Crop monitoring
  • Hydrology – Wetland assessment
  • Environment – Oil spill, hazard monitoring
  • Archaeology – Sub-surface mapping