WE3.L09 - RAIN EFFECT ON POLARIMETRIC SAR OBSERVATION
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WE3.L09 - RAIN EFFECT ON POLARIMETRIC SAR OBSERVATION

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WE3.L09 - RAIN EFFECT ON POLARIMETRIC SAR OBSERVATION WE3.L09 - RAIN EFFECT ON POLARIMETRIC SAR OBSERVATION Presentation Transcript

  • RAIN EFFECT ON POLARIMETRIC SAR OBSERVATION Hiroaki Yasuma and Hajime Fukuchi Tokyo Metropolitan University Dept. of Aerospace Engineering July 28, 2010
  • INTRODUCTION (1) Distortions in the SAR observational data come from various factors. Absorption by the atmosphere ( oxygen, water vapor, and so on. ) Scattering by the weather particle ( Rain, snow, fog, and hail, etc. ) It is essential to know the radio propagation characteristics. Faraday Rotation (FR) ( Phenomenon of polarization rotation ) Observation Frequency Example of SAR Meteorological Particle FR X-Band TerraSAR-X (9.65 GHz) Important Negligible Negligible Important C-Band RADARSAT-2 (5.405GHz) L-Band PALSAR (1.27GHz)
  • INTRODUCTION (2)
    • High-frequency and high-resolution SAR such as TerraSAR-X (9.65GHz, 1m resolution) is successful
    • these days.
    • As frequency increases,
    • the rain effects cannot be ignored.
    • Quantitative evaluations of these effects are scarce and thus needed.
    TerraSAR-X. © EADS Astrium
  • IN CASE OF TerraSAR-X
    • Excerpt from “On The Impact of Precipitation on Space-borne SAR Imaging: Recent Measurement with TerraSAR-X”, Andreas Danklmayer, Madhukar Chandra.
    • Give the POLSAR observation model and estimate the effects at several conditions:
    PURPOSE OF RESEARCH Evaluate the effects of rain quantitatively ・ Observation frequency ・ Rainfall rate ・ Incident angle ・ Canting angle of rain drops ・ Rain area length
  • POLSAR OBSERVATION MODEL The scattering matrix S sequentially receives turbulence in the propagation route. Ice Layer P: Ice Distortion Matrix Ionosphere F: Faraday Rotation Receive Antenna R Transmit Antenna T Rainfall Q: Rain Distortion Matrix Land Surface S: Scattering Matrix When rainfall is the only error source If Q is computable with already known S , M can be obtained
  • THE RAIN EFFECT AREA
    • The radio wave is absorbed and scattered by rain drops in area A .
    SAR Rainfall Area A Rain drops Rainfall SAR Area B
    • Rain drops in area B promote the additional backscatter as well.
  • THE MAJOR THREE EFFECTS BY RAIN
    • Attenuation: | Q HH |
      • Because of the scattering and absorption by the rain drops
    • Attenuation Ratio: | Q VV / Q HH |
      • Because of the non-spherical rain drop shape
    • Depolarization: | Q HV / Q HH |
      • Because of the non-spherical rain drop shape and
      • the canting angle of the rain drop
  • ATTENUATION RATIO
    • The horizontal polarization (H) is attenuated more greatly than the vertical one (V) because of the non-spherical rain drop shape.
    • Attenuation ratio between H and V: | Q VV / Q HH |
    Incident waves Attenuated waves H passes through the rain drop more than V. Rain drop
  • DEPOLARIZATION
    • The depolarization occurs because of the non-spherical rain drop shape and the canting angle of the rain drop.
    • | Q HV / Q HH | represents the amount of this depolarization.
    Canting angle Incident wave Attenuated wave
  • ESTIMATE THE RAIN DISTORTION MATRIX (Q)
    • Calculation Condition:
    Derivation of Q : Oguchi’s method* Rain Shape: Pruppacher-and-Pitter Drop Size Distribution: Marshall-and-Palmer Rain Area Length: 5 km Incident Angle: 40° Canting Angle: 0 ° or 45 ° Scattering Matrix : (Plate or Trihedral) * Tomohiro Oguchi, “Scattering properties of Pruppacher-and-Pitter form rain drops and cross polarization due to rain: Calculation at 11, 13, 19.3 and 34.8GHz,” Radio Science , vol. 12, no. 1, pp. 41-51, 1977.       1 0 0 1
  • ESTIMATION RESULTS: RAIN-INDUCED ATTENUATION
    • | Q HH | represents the amount of the rain-induced attenuation.
    Canting angle: 0° Rain Attenuation [dB/km]
  • ESTIMATION RESULTS: ATTENUATION RATIO Canting angle: 0°
    • | Q VV / Q HH | represents the attenuation ratio between H and V.
  • ESTIMATION RESULTS: DEPOLARIZATION Canting angle: 45°
    • | Q HV / Q HH | represents the amount of the depolarization.
  • ESTIMATION RESULTS: POLARIZATION SIGNATURE
    • Calculation Condition:
    Rain rate: 50 [mm/h] Canting Angle: 22.5° Derivation of Q : Oguchi’s method Rain Shape: Pruppacher-and-Pitter Drop Size Distribution: Marshall-and-Palmer Rain Area Length: 5 km Incident Angle: 40° Scattering Matrix : (Plate or Trihedral)       1 0 0 1
  • Trihedral (or Plate) Reflector: S= Co-pol. Cross pol. Ideal
  • Trihedral (or Plate) Reflector: S= 5.405 [GHz] Co-pol. Cross pol.
  • Trihedral (or Plate) Reflector: S= Co-pol. Cross pol. 9.65 [GHz]
  • Trihedral (or Plate) Reflector: S= Co-pol. Cross pol. 13.9 [GHz]
  • CONCLUSIONS
    • The rain effect on POLSAR observation was quantitatively evaluated using the SAR observation model in non-spherical rain drop environments.
    • The results show that the rain attenuation, the attenuation ratio and the depolarization increase as the frequency and rainfall rate increase , and that they also depend on the rain drop canting angle .
  • REFERENCES
    • Andreas Danklmayer, Madhukar Chandra, “On The Impact of Precipitation on Space-borne SAR Imaging: Recent Measurement with TerraSAR-X”
    • Andreas Danklmayer, Bjorn J. Doring, Marco Schwerdt, and Madhu Chandra, “Assessment of Atmospheric Propagation Effects in SAR Images,” IEEE Trans. Geosci. Remote Sensing , vol. 47, pp. 3507-3518, 2009.
    • Tomohiro Oguchi, “Scattering properties of Pruppacher-and-Pitter form rain drops and cross polarization due to rain: Calculation at 11, 13, 19.3 and 34.8GHz,” Radio Science , vol. 12, no. 1, pp. 41-51, 1977.