IGARSS11_FFBP_CSAR_v3.ppt

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IGARSS11_FFBP_CSAR_v3.ppt

  1. 1. Octavio Ponce, Pau Prats , Marc Rodriguez-Cassola, Rolf Scheiber, Andreas Reigber Microwave and Radar Institute (HR) German Aerospace Center Processing of Circular SAR Trajectories with Fast Factorized Back-Projection
  2. 2. Outline <ul><li>Circular SAR (CSAR) </li></ul><ul><li>Fast Factorized Back Projection (FFBP) </li></ul><ul><li>FFBP for Circular SAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Conclusions </li></ul>
  3. 3. Acquisition Geometry .
  4. 4. Resolution – Stripmap 2D IRF 2D Sinc Time Domain Frequency Domain y x
  5. 5. Resolution – CSAR 2D IRF Time Domain Frequency Domain Soumekh et al, IEEE TIP, 1996 y x
  6. 6. Resolution – CSAR 1D IRF CSAR L-Band Stripmap L-Band
  7. 7. Tomography CSAR <ul><li>Similar to Computer-aided Tomography 360° </li></ul><ul><li>Resolves altitude ambiguities </li></ul><ul><li>Shadow “removal” </li></ul>Terrain y x z
  8. 8. Tomography CSAR– Simulated 3D IRF 3D 2D Slice Surface – 2D Slice Ishimaru, IEEE TGRS, 1998 y x y x z
  9. 9. Outline <ul><li>Circular SAR (CSAR) </li></ul><ul><li>Fast Factorized Back Projection (FFBP) </li></ul><ul><li>FFBP for Circular SAR </li></ul><ul><li>Experimental Setup and Results </li></ul><ul><li>Conclusions </li></ul>
  10. 10. Challenges of CSAR Processing <ul><li>Topography accommodation </li></ul><ul><li>Real Track </li></ul><ul><li>Time efficient algorithm </li></ul><ul><li>High accuracy in amplitude and phase </li></ul>
  11. 11. Fast Factorized Back Projection (FFBP) <ul><li>Key points of FFBP (L. Ulander et al. , IEEE TAES 2003): </li></ul><ul><li>Recursive division of the synthetic aperture (no cost) </li></ul><ul><li>After the division, the smallest sub-apertures are back-projected on a polar grid centred on each sub-aperture (~N 3 /2 k ) </li></ul><ul><li>Recursive addition of the sub-apertures by means of interpolations between polar grids (quality-dependent) </li></ul>
  12. 12. Fast Factorized Back Projection (FFBP) Ulander et al, IEEE TAES, 2003 L/8 L/8 L/8 L/8 L/8 L/8 L/4 L/4 L/2 L/4 L/4 L/2 L/8 L/8 L FOCUSED IMAGE Lm BP P2P P2P P2P P2Final Grid k=1 k=2 k=3
  13. 13. Why Polar Coordinates? Spatial Domain (small sub-aperture) Frequency Domain Polar to Cartesian 2D FFT 2D FFT
  14. 14. x … FFBP for Spotlight/Stripmap – P2P y x z
  15. 15. Outline <ul><li>Circular SAR (CSAR) </li></ul><ul><li>Fast Factorized Back Projection (FFBP) </li></ul><ul><li>FFBP for Circular SAR </li></ul><ul><li>Experimental Setup and Results </li></ul><ul><li>Conclusions </li></ul>
  16. 16. Modifications of FFBP for CSAR <ul><li>The orientation of the polar grid for each sub-aperture changes following the circular trajectory. </li></ul><ul><li>The polar-to-polar interpolation needs to project first to ground coordinates and then back to the new polar centre. </li></ul><ul><li>The DEM must be generated (interpolated) for each polar centre. </li></ul>
  17. 17. FFBP for CSAR - Geometry Top View x y
  18. 18. FFBP for CSAR - Geometry Top View x y
  19. 19. FFBP CSAR - P2P Interpolation Zoom Top View to Ground range Project Translate Rotate Get and
  20. 20. FFBP for CSAR - Geometry Top View .
  21. 21. Outline <ul><li>Circular SAR (CSAR) </li></ul><ul><li>Fast Factorized Back Projection (FFBP) </li></ul><ul><li>FFBP for Circular SAR </li></ul><ul><li>Experimental Results </li></ul><ul><li>Conclusions </li></ul>
  22. 22. FFBP CSAR - Simulation . 700m Terrain 4000m Height 4500m Radius 94MHz BW L Band 400Hz PRF
  23. 23. FFBP CSAR - Simulation *Interpolator  Knab Pulse of 21 points BP vs FFBP Knab, IEEE TIT, 1979
  24. 24. FFBP CSAR - Performance Speed Up System, Geometry, Hardware, Interpolator BP CPU  ~238days 25000 x 25000 pixels ~3 hrs FFBP GPU ~11 hrs FFBP CPU ~3 days BP GPU Speed up factor
  25. 25. <ul><li>DLR’s (German Aerospace Center) E-SAR System </li></ul><ul><li>Lidar DEM available </li></ul><ul><li>Kaufbeuren, Germany (2008) </li></ul><ul><li>Fully Polarimetric: HH - HV - VV </li></ul><ul><li>Carrier Frequency: 1.3GHz (L-Band) </li></ul><ul><li>Bandwidth: 94MHz </li></ul><ul><li>Height Mean: ~3,200m </li></ul><ul><li>Circle Radius: ~4,500m </li></ul><ul><li>Roll Angle: ~10° </li></ul><ul><li>Depression Angle: ~30° </li></ul>Experimental Setup
  26. 26. Experimental Results - BP vs FFBP Optical Image CSAR Image 150 x 150 m; Δφ =360°
  27. 27. Experimental Results - BP vs FFBP 1.0 0.99 10° -10° 0° Coherence Interferogram 0.000599 Coh. Std. Dev. 1.7 ° Phase Std. Dev.
  28. 28. Polarimetric Results - Subapertures Pauli 1240 x 1240 m; Δφ =10°
  29. 29. CSAR vs Strimap SAR 1500 x 1500 m E-SAR L-band, 94MHz bandwidth
  30. 30. CSAR vs Strimap SAR E-SAR L-band, 94MHz bandwidth
  31. 31. E-SAR L-band, 94MHz bandwidth CSAR vs Strimap SAR
  32. 32. E-SAR L-band, 94MHz bandwidth CSAR vs Strimap SAR 180 x 180 m
  33. 33. E-SAR L-band, 94MHz bandwidth Circular SAR vs Strimap SAR 180 x 180 m
  34. 34. DEM + 0m Tomography CSAR DEM + 2m DEM + 3m DEM + 4m E-SAR L-band, 94MHz bandwidth
  35. 35. Luneberg Lens 1500 x 1500 m
  36. 36. Tree E-SAR L-band, 94MHz bandwidth Tomography CSAR -5m < H < 15m 300 x 300 m
  37. 37. <ul><li>FFBP adapted to CSAR successfully: </li></ul><ul><ul><li>Topography accommodation </li></ul></ul><ul><ul><li>Real track </li></ul></ul><ul><ul><li>High improvement in the Speed-up Factor </li></ul></ul><ul><ul><li>High accuracy </li></ul></ul><ul><li>Implementation in a graphic processor unit (GPU) </li></ul><ul><li>Experimental results with DLR’s E-SAR data have been used to validate the algorithm </li></ul><ul><li>Currently processing new “multi-circular” F-SAR campaign </li></ul>Conclusions
  38. 38. Thanks for your attention! <ul><li>Octavio Ponce: [email_address] </li></ul><ul><li>Pau Prats: [email_address] </li></ul><ul><li>DLR (German Aerospace Center) </li></ul><ul><li>HR (Microwaves and Radar Institute) </li></ul>
  39. 39. References <ul><li>H. Oriot, H. Cantalloube, “Circular SAR imagery for urban remote sensing” , EUSAR 2008. </li></ul><ul><li>A. Ishimaru, Chan, Kuga, “An Imaging Technique Using Confocal Circular Synthetic Aperture Radar”, IEEE Transactions on Geoscience and Remote Sensing, Vol. 36, No.5, Septemper 1998. </li></ul><ul><li>M. Soumekh, “Synthetic Aperture Radar Signal Processing with Matlab Algorithms”, John Wiley & Sons, Inc. </li></ul><ul><li>M. Pinheiro, P. Prats, R. Scheiber, M. Nannini, and A. Reigber, “Tomographic 3D reconstruction from airborne circular SAR,” in Geoscience and Remote Sensing Symposium, 2009 IEEE International, IGARSS 2009, 2009, vol. 3, pp. III–21 – III–24. </li></ul><ul><li>Lars M. H. Ulander and et. al., “Synthetic-Aperture Radar Processing Using Fast Factorized Back-Projection,” IEEE Transactions on Aerospace and Electronic Systems, vol. 39, no. 3, pp. 760–776, July 2003. </li></ul><ul><li>M. Rodriguez-Cassola, P. Prats, G. Krieger, and A. Moreira, “Efficient Time-Domain Focussing for General Bistatic SAR Configurations: Bistatic Fast Factorised Backprojection,” in European Conference on Synthetic Aperture Radar (EUSAR), Jun 2010. </li></ul>
  40. 40. FFBP for CSAR – Computational Load
  41. 41. Knab Pulse Band-Limited Interpolation Knab, IEEE TIT, 1979
  42. 42. Hardware CC 2.0 1.15GHz 2.4GHz Clock 488 8 Cores 6GB 24GB RAM Tesla® C2070 Intel® Xeon® Processor GPU CPU
  43. 43. Acquisition Geometry Integrated reflectivity = reflectivity function * transmitted radar signal
  44. 44. Experimental Results Illumination Flight Track -60dB 0dB -6000 [m] 0 6000 -6000 0 6000 [m]
  45. 45. FFBP for CSAR – 2D Spectrum Polar 0.70° 1.40° 2.81° 5.62° 11.25° 22.5° 45° 90° 180°
  46. 46. FFBP for CSAR – Flow diagram

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