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SAR image simulation in the time domain for moving ocean surfaces.

Yoshida T, Rheem CK - Sensors (Basel) (2013)

Bottom Line: In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves.The simulation results are in good agreement with the theory.These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Ocean Technology, Policy and Environment, The University of Tokyo, Tokyo, Japan. tyoshida@iis.u-tokyo.ac.jp

ABSTRACT
This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces. We have designed the simulation based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images. The time domain simulation is able to obtain time series of microwave backscattering modulated by the orbital motions of ocean waves. Physical optics approximation is applied to calculate microwave backscattering. The computational grids are smaller than transmit microwave to demonstrate accurate interaction between electromagnetic waves and ocean surface waves. In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves. The SAR images of stationary and moving targets are simulated to confirm SAR signal processing and motion induced modulation. Furthermore, the azimuth signals from the regular wave traveling to the azimuth direction also show the azimuthal shifts due to the orbital motions. In addition, incident angle dependence is simulated for irregular wind waves to compare with Bragg scattering theory. The simulation results are in good agreement with the theory. These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.

No MeSH data available.


Related in: MedlinePlus

Influence Bragg resonant wave on microwave backscattering (Bragg resonant condition of 42 degrees). (a) Real part of SAR raw signal; (b) SAR intensity.
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f14-sensors-13-04450: Influence Bragg resonant wave on microwave backscattering (Bragg resonant condition of 42 degrees). (a) Real part of SAR raw signal; (b) SAR intensity.

Mentions: To examine the influence of Bragg scattering, the simulation is carried out in the case of the regular waves whose wavelengths are satisfied with the Bragg resonant condition as described in Equation (9). The SAR raw signals in the range direction are simulated for the regular Bragg resonant waves traveling to the range direction (see Figure 11). The simulation conditions are as follows. The incident angles are 36 to 44 degrees. The radar wavelength is 0.235 m. The wavelengths of the regular ocean waves are 0.191, 0.183, 0.176 m, which are the Bragg resonant waves of 38, 40, 42 degrees, respectively. The amplitude is 0.001 m in these three cases. The calculation area in the azimuth direction is 4.7 m. The other conditions of the simulation are the same as Table 1. The SAR raw signals and their compressed signals are shown in Figures 12, 13 and 14.


SAR image simulation in the time domain for moving ocean surfaces.

Yoshida T, Rheem CK - Sensors (Basel) (2013)

Influence Bragg resonant wave on microwave backscattering (Bragg resonant condition of 42 degrees). (a) Real part of SAR raw signal; (b) SAR intensity.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3673093&req=5

f14-sensors-13-04450: Influence Bragg resonant wave on microwave backscattering (Bragg resonant condition of 42 degrees). (a) Real part of SAR raw signal; (b) SAR intensity.
Mentions: To examine the influence of Bragg scattering, the simulation is carried out in the case of the regular waves whose wavelengths are satisfied with the Bragg resonant condition as described in Equation (9). The SAR raw signals in the range direction are simulated for the regular Bragg resonant waves traveling to the range direction (see Figure 11). The simulation conditions are as follows. The incident angles are 36 to 44 degrees. The radar wavelength is 0.235 m. The wavelengths of the regular ocean waves are 0.191, 0.183, 0.176 m, which are the Bragg resonant waves of 38, 40, 42 degrees, respectively. The amplitude is 0.001 m in these three cases. The calculation area in the azimuth direction is 4.7 m. The other conditions of the simulation are the same as Table 1. The SAR raw signals and their compressed signals are shown in Figures 12, 13 and 14.

Bottom Line: In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves.The simulation results are in good agreement with the theory.These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Ocean Technology, Policy and Environment, The University of Tokyo, Tokyo, Japan. tyoshida@iis.u-tokyo.ac.jp

ABSTRACT
This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces. We have designed the simulation based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images. The time domain simulation is able to obtain time series of microwave backscattering modulated by the orbital motions of ocean waves. Physical optics approximation is applied to calculate microwave backscattering. The computational grids are smaller than transmit microwave to demonstrate accurate interaction between electromagnetic waves and ocean surface waves. In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves. The SAR images of stationary and moving targets are simulated to confirm SAR signal processing and motion induced modulation. Furthermore, the azimuth signals from the regular wave traveling to the azimuth direction also show the azimuthal shifts due to the orbital motions. In addition, incident angle dependence is simulated for irregular wind waves to compare with Bragg scattering theory. The simulation results are in good agreement with the theory. These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.

No MeSH data available.


Related in: MedlinePlus