Airborne Holographic SAR Tomography
at L- and P-band
O. Ponce, A. Reigber and A. Moreira.
Microwaves and Radar Institute (HR),
German Aerospace Center (DLR).
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Outline
• Introduction to 3-D SAR
• Holographic SAR Tomography (HoloSAR)
• Theory and Imaging Approaches
• Experimental Realizations
• Conclusions
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Introduction – 3-D SAR Imaging
SAR Interferometry (InSAR)
SAR Tomography (SARTom)
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Introduction – 3-D SAR Imaging
SAR Interferometry (InSAR)
SAR Tomography (SARTom)
Retrieved Information:
Retrieved Information:
• Height
• Complex reflectivity
• Single aspect angle
• Resolution in 𝑛
• Single aspect angle
Digital Elevation Model (DEM) of Iceland, 2011.
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Introduction – 3-D SAR Imaging
Circular SAR (CSAR)
Holographic SAR Tomography (HoloSAR)
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Introduction – 3-D SAR Imaging
Circular SAR (CSAR)
Holographic SAR Tomography (HoloSAR)
Retrieved Information:
Retrieved Information:
• Complex reflectivity
• Complex reflectivity
• Resolution in 𝑧
• Resolution in 𝑧
• Multiple aspect angles
• Multiple aspect angles
• Sub-𝜆 resolution in (𝑥, 𝑦)
• Sub-𝜆 resolution in (𝑥, 𝑦)
• Low resolution in 𝑛
• High resolution in 𝑛
Impulse Response Function - Luneburg Lens
Impulse Response Function - Luneburg Lens
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Introduction – Linear SAR VS Circular SAR
Stripmap SAR
Circular SAR
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Experimental Realizations - Circular SAR – L-band
Circular SAR
Stripmap SAR
Pauli basis, Coherent imaging, 500 m x 500 m, 0.06 m by 0.06 m sampling
E-SAR L-Band, bandwidth 95MHz
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Theory on HoloSAR – Impulse Response Function
• Ambiguities
• Resolution
Gatelli, et al, The wavenumber shift in SAR interferometry, IEEE TGRS, 1994.
Reigber, et al, First demonstration of Airborne SAR Tomography using Multi-baseline L-band data, IEEE TGRS, 2000.
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Theory on HoloSAR – Impulse Response Function
• (𝑥, 𝑦) IRF
• 𝑧 IRF
• Bandwidth enhancement
F. Gatelli, et al, The wavenumber shift in SAR interferometry, IEEE TGRS, 1994.
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Spectrum of HoloSAR - k space
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Theory on HoloSAR – Impulse Response Function
1 track
3 tracks, ∆𝐵 = 150 m
19 tracks, ∆𝐵 = 12 m
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Theory on HoloSAR – Imaging Approaches
1
2
3
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2014, in press.
O. Ponce, et al, Analysis and optimisation of multi-circular SAR for fully polarimetric holographic tomography over forested areas, IGARSS 2013.
O. Ponce, et al, Polarimetric 3-D Reconstruction from Multi-Circular SAR at P-band, GRSL 2014 .
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Theory on HoloSAR – Imaging Approaches
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Compressive Sensing (CS)
Beamforming (BF)
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Coherent Addition - Fourier
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Generalized Likelihood Ratio (GLRT)
Incoherent Addition
Holographic SAR Tomogram
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2014, in press.
O. Ponce, et al, Analysis and optimisation of multi-circular SAR for fully polarimetric holographic tomography over forested areas, IGARSS 2013.
O. Ponce, et al, Polarimetric 3-D Reconstruction from Multi-Circular SAR at P-band, GRSL 2014 .
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Experimental Realizations – HoloSAR at P-band
F-SAR System
3-D HoloSAR Tracks
Campaign
Polarisations
HH, HV, VH, VV
Central Frequency
P-Band
Chirp Bandwidth
20 MHz
PRF
500 Hz
Circular passes
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Max. Baseline [m]
110 m
Radius avg.
3800 m
Region
Vordemwald, CH.
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Experimental Realizations – HoloSAR at P-band
Pauli basis, 𝟐. 𝟔 km diameter, 𝟎. 𝟎𝟔 m by 𝟎. 𝟎𝟔 m sampling
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Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices
Subaperture, Fourier + Incoherent
Fourier + Incoherent
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Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices
CS + Incoherent
Fourier + Incoherent
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Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices
CS + Incoherent
Fourier + Incoherent
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Forested area - 𝟕 tracks – Fourier + Incoherent – (𝒙, 𝒛) slices
Lexicographic (red line LIDAR)
Span
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Forested area - 𝟕 tracks – CS + Incoherent – (𝒙, 𝒛) slices
Lexicographic (red line LIDAR)
Span
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Forested area - 𝟕 tracks – CS + Incoherent – 3-D View
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Experimental Realizations – HoloSAR at L-band
F-SAR System
3-D HoloSAR Tracks
Campaign
Polarisations
HH, HV, VH, VV
Central Frequency
L-Band
Chirp Bandwidth
50 MHz
PRF
500 Hz
Circular passes
19
Max. Baseline [m]
285 m
Radius avg.
3700 m
Region
Kaufbeuren, DE.
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Experimental Realizations – HoloSAR at L-band
Pauli basis, 𝟏. 𝟐 km diameter, 𝟎. 𝟎𝟔 m by 𝟎. 𝟎𝟔 m sampling
1) 15 x 15 x 50 m, 2) 300 x 300 x 50 m
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Experimental Realizations – HoloSAR at L-band
Single Tree – Pauli basis – 15 x 15 x 50 m
1 track
3 tracks, ∆𝐵 = 150 m
19 tracks, ∆𝐵 = 12 m
2521
Experimental Realizations – HoloSAR at L-band
Forested Area – 𝟏𝟗 Tracks - Pauli basis
Compressive Sensing + GLRT
Compressive Sensing + Incoherent
Coherent
2621
Forested area - 𝟏𝟗 tracks – Pauli - 2-D slices – 𝒚 = 𝟐𝟎𝟓. 𝟓 m
Compressive Sensing + GLRT
Compressive Sensing + Incoherent
Coherent
* red line  LIDAR
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Forested area - 𝟏𝟗 tracks – Pauli - 2-D slices – 𝒚 = 𝟏𝟎𝟓. 𝟓 m
Compressive Sensing + GLRT
Compressive Sensing + Incoherent
Coherent
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Forested area – Pauli - 𝟏𝟗 tracks – 2-D slices - 𝒛 = 𝟕𝟕𝟖/𝟖𝟎𝟏 m
Compressive Sensing + GLRT Compressive Sensing + Incoherent
Coherent
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Forested area – Pauli - 𝟏𝟗 tracks – 3-D view
Compressive Sensing + Incoherent
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Conclusions
• HoloSAR offers unique means to get the full 3-D backscattering over 360°.
• Improvement of the effective BW by taking into account the several circular
passes with vertical or horizontal separation
• Theory is validated with Airborne acquisitions at L- and P-band over forests.
• HoloSAR can be used as a powerful tool to measure biophisical parameters,
and to reduce uncertainties of conventional 3-D SAR modes
• Potential for Future Earth Observation Space Missions
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L-Band image with 6 cm sampling
What are you seeing here?
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DLR’s airborne SAR – L-Band quad pol
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Pauli basis, 1.8 km diameter, 0.06 m by 0.06 m sampling
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Thanks for your attention!
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Back Up Slides
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References
M. Soumekh, Synthetic Aperture Radar Signal Processing: with MATLAB Algorithms, John Wiley & Sons, 1999.
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2013, in press.
L. J. Moore, et al, An analytical expression for the three-dimensional response of a point scatterer for CSAR, SPIE, 2010.
D. C. Munson, et al, A tomographic formulation of spotlight-mode synthetic aperture radar, Proc. of IEEE, 1983.
H. E. Knutsson, et al, Ectomography a new radiographic reconstruction method, IEEE Trans. Biomed. Engi., 1980.
P. Ferraro, et al, Coherent Light Microscopy: Imaging and Quantitative Phase Analysis, Springer-Verlag, 2011.
S. Guillaso, et al, Range Resolution improvement of Airborne SAR Images, IEE GRSL, 2006.
O. Ponce, et al, Polarimetric 3-D Reconstruction from Multi-Circular SAR at P-band, GRSL 2014.
E. Ertin, et al, GOTCHA experience report: 3-D SAR imaging with complete circular apertures, SPIE, 2007.
Reigber, et al, First demonstration of Airborne SAR Tomography using Multi-baseline L-band data, IEEE TGRS, 2000.
F. Gatelli, et al, The wavenumber shift in SAR interferometry, IEEE TGRS, 1994.
G. Groh, Holographic tomography using a circular synthetic aperture, Applied optics, vol.10,no.11,1971.
J. K. Glanzer, et al, A comparison between Holographic SAR (HSAR) and Conventional Narrow Angle SAR,
EARSeL, 2013.
O. Ponce, et al, First demonstration of 3-D holographic tomography with fully polarimetric multi-circular SAR at L-band,
IGARSS 2013.
O. Ponce, et al, Analysis and optimization of multi-circular SAR for fully polarimetric holographic tomography over forested
areas , IGARSS 2013.
36
Spectrum of HoloSAR for different wavelengths
Band
Indicator
P (350 MHz)
Small blue
L (1.3 GHz)
Small black
S (3.25 GHz)
Red
C (5.3 GHz)
Blue
X (9.6 GHz)
Black
Parameter
Value
Height
2000 m
Radius
4000 m
Sys. Bandwidth 50 MHz
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2013, in press.
37
Impulse Response Function (IRF) – HoloSAR
• Back Projection Equation
data acquisition
processing
• (x,y) IRF for a target in p=(0,0,0)
:
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2013, in press.
L. J. Moore, et al, An analytical expression for the three-dimensional response of a point scatterer for CSAR, SPIE, 2010.
38
Impulse Response Function (IRF) – HoloSAR
• Back Projection Equation
data acquisition
processing
• (x,y) IRF for a target in p=(0,0,0)
• z IRF for a target in p=(0,0,0)
:
O. Ponce, et al, Fully-Polarimetric High-Resolution 3-D imaging with CSAR at L-band, TGRS, 2013, in press.
L. J. Moore, et al, An analytical expression for the three-dimensional response of a point scatterer for CSAR, SPIE, 2010.
39
Spectrum of HoloSAR - k space
40
Spectrum of HoloSAR
• (x,y) IRF
• z IRF
• Bandwidth improvement
F. Gatelli, et al, The wavenumber shift in SAR interferometry,, IEEE TGRS, 1994.
41
Spectrum of HoloSAR
• Ambiguities
• Resolution
F. Gatelli, et al, The wavenumber shift in SAR interferometry, IEEE TGRS, 1994.
Reigber, et al, First demonstration of Airborne SAR Tomography using Multi-baseline L-band data,
IEEE TGRS, 2000.
42
Spectrum of HoloSAR - Simulation Geometry
Parameter
Value
Height
2000 m
Radius
4000 m
Sys. Bandwidth 50 MHz
∆𝐵 critical
358 m
Band
L (0.24 m)
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Spectrum - Target IN the center (x,yz) = (0,0,0)
3 tracks -
9 tracks -
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Spectrum - Target OFF the center (x,y,z) = (500,500,0)
3 tracks -
9 tracks -
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Impulse Response Function – HoloSAR
Time domain
Spectrum
Parameter
Value
No. tracks
1
Sidelobe Pwr
-13 dB
Effective BW
50 MHz
ΔB
----
Luneburg lens
46
Impulse Response Function – HoloSAR
Time domain
Spectrum
Parameter
Value
No. tracks
3
Sidelobe Pwr
-13 dB
Effective BW
125 MHz
ΔB
150 m
Luneburg lens
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Impulse Response Function – HoloSAR
Time domain
Spectrum
Parameter
Value
No. tracks
19
Sidelobe Pwr
-25 dB
Effective BW
125 MHz
ΔB
12 m
Luneburg lens
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Holographic Tomography (HT) with Multi-Circular SAR
(MCSAR)
MCSAR Geometry
Similarities with optical HT
• Imaging of the internal structure of the scene.
• Acquisition geometry with 2 synthetic
apertures.
• Resolution enhancement by both synthetic
apertures.
• Every measurement corresponds to a
microwave hologram, since it contains
information of the image as a whole.
• Imaging through the projection-slice theorem*.
*
K. K. Knael, et al, Radar tomography for the generation of three-dimensional images, IEEE Proc.-Rad. Son.Navi.,1995.
P. Ferraro, et al, Coherent Light Microscopy: Imaging and Quantitative Phase Analysis, Springer-Verlag, 2011.
G. Groh, Holographic tomography using a circular synthetic aperture, Applied optics, vol.10,no.11,1971.
49
Computed Axial Tomography (CAT)
2-D Geometry
3-D Geometry
D. C. Munson, et al, A tomographic formulation of spotlight-mode synthetic aperture radar, Proc. of IEEE, 1983.
50
Ectomography – Single Rotation / Acquisition
Geometry
Spectrum
Impulse Response Function (IRF)
H. E. Knutsson, et al, Ectomography a new radiographic reconstruction method, IEEE Trans. Biomed. Engi., 1980.
51
Circular SAR (CSAR) – Single Rotation / Acquisition
Geometry
Spectrum
Impulse Response Function (IRF)
K. K. Knael, et al, Radar tomography for the generation of three-dimensional images, IEEE Proc.-Rad. Son.Navi.,1995.
52
Holographic Tomography – Multiple Rotation
Spectrum Single
Spectrum Multiple
P. Ferraro, et al, Coherent Light Microscopy: Imaging and Quantitative Phase Analysis, Springer-Verlag, 2011.
G. Groh, Holographic tomography using a circular synthetic aperture, Applied optics, vol.10,no.11,1971.
53
Holographic Tomography with
Multi-Circular SAR (SAR)
CSAR
MCSAR
K. K. Knael, et al, Radar tomography for the generation of three-dimensional images, IEEE Proc.-Rad. Son.Navi.,1995.
54
Holographic Tomography with MCSAR
IRF CSAR
IRF MCSAR
Spectrum
Spectrum
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