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). 1 Outline • Introduction to 3-D SAR • Holographic SAR Tomography (HoloSAR) • Theory and Imaging Approaches • Experimental Realizations • Conclusions 2 Introduction – 3-D SAR Imaging SAR Interferometry (InSAR) SAR Tomography (SARTom) z B 1 z x 2 1 2. . . N n n r r h y x h y 3 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. 4 Introduction – 3-D SAR Imaging Circular SAR (CSAR) Holographic SAR Tomography (HoloSAR) z z 1 2. . . N n n r r x h y x h y 5 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 6 Introduction – Linear SAR VS Circular SAR Stripmap SAR Circular SAR 7 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 8 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. 9 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. 10 Spectrum of HoloSAR - k space 11 Theory on HoloSAR – Impulse Response Function 1 track 3 tracks, ∆𝐵 = 150 m 19 tracks, ∆𝐵 = 12 m 12 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 . 13 Theory on HoloSAR – Imaging Approaches .. . .. . Compressive Sensing (CS) Beamforming (BF) .. . 1 2 Coherent Addition - Fourier 3 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 . 14 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 7 Max. Baseline [m] 110 m Radius avg. 3800 m Region Vordemwald, CH. 15 Experimental Realizations – HoloSAR at P-band Pauli basis, 𝟐. 𝟔 km diameter, 𝟎. 𝟎𝟔 m by 𝟎. 𝟎𝟔 m sampling 16 Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices Subaperture, Fourier + Incoherent Fourier + Incoherent 17 Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices CS + Incoherent Fourier + Incoherent 18 Forested area - 𝟕 tracks – Span – (𝒙, 𝒚) slices CS + Incoherent Fourier + Incoherent 19 Forested area - 𝟕 tracks – Fourier + Incoherent – (𝒙, 𝒛) slices Lexicographic (red line LIDAR) Span 20 Forested area - 𝟕 tracks – CS + Incoherent – (𝒙, 𝒛) slices Lexicographic (red line LIDAR) Span 21 Forested area - 𝟕 tracks – CS + Incoherent – 3-D View 22 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. 23 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 24 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 27 Forested area - 𝟏𝟗 tracks – Pauli - 2-D slices – 𝒚 = 𝟏𝟎𝟓. 𝟓 m Compressive Sensing + GLRT Compressive Sensing + Incoherent Coherent 28 Forested area – Pauli - 𝟏𝟗 tracks – 2-D slices - 𝒛 = 𝟕𝟕𝟖/𝟖𝟎𝟏 m Compressive Sensing + GLRT Compressive Sensing + Incoherent Coherent 29 Forested area – Pauli - 𝟏𝟗 tracks – 3-D view Compressive Sensing + Incoherent 3027 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 31 L-Band image with 6 cm sampling What are you seeing here? 32 DLR’s airborne SAR – L-Band quad pol 1 2 3 4 1 3 2 4 Pauli basis, 1.8 km diameter, 0.06 m by 0.06 m sampling 33 Thanks for your attention! 34 Back Up Slides 35 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) 43 Spectrum - Target IN the center (x,yz) = (0,0,0) 3 tracks - 9 tracks - 44 Spectrum - Target OFF the center (x,y,z) = (500,500,0) 3 tracks - 9 tracks - 45 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 47 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 48 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 55
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