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Remote Sens. 2017, 9(3), 219; doi:10.3390/rs9030219

Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images

1,2,3
,
4,* , 1,2,* , 1,2,3
and
1,2,3
1
National Key Laboratory of Science and Technology on Microwave Imaging, Beijing 100190, China
2
Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China
3
School of Electronics, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
4
Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
*
Authors to whom correspondence should be addressed.
Academic Editors: Xiaofeng Yang, Xiaofeng Li, Ferdinando Nunziata, Alexis Mouche and Prasad S. Thenkabail
Received: 6 December 2016 / Revised: 24 February 2017 / Accepted: 25 February 2017 / Published: 28 February 2017
(This article belongs to the Special Issue Ocean Remote Sensing with Synthetic Aperture Radar)
View Full-Text   |   Download PDF [4769 KB, uploaded 28 February 2017]   |  

Abstract

The image intensities of low-backscattering areas in synthetic aperture radar (SAR) images are often seriously contaminated by the system noise floor and azimuthal ambiguity signal from adjacent high-backscattering areas. Hence, the image intensity of low-backscattering areas does not correctly reflect the backscattering intensity, which causes confusion in subsequent image processing or interpretation. In this paper, a method is proposed to estimate the normalized radar cross-section (NRCS) of low-backscattering area by utilizing the differences between noise, azimuthal ambiguity, and signal in the Doppler frequency domain of single-look SAR images; the aim is to eliminate the effect of system noise and azimuthal ambiguity. Analysis shows that, for a spaceborne SAR with a noise equivalent sigma zero (NESZ) of −25 dB and a single-look pixel of 8 m × 5 m, the NRCS-estimation precision of this method can reach −38 dB at a resolution of 96 m × 100 m. Three examples are given to validate the advantages of this method in estimating the low NRCS and the filtering of the azimuthal ambiguity. View Full-Text
Keywords: SAR; ocean; NRCS; Doppler spectrum; azimuthal ambiguity SAR; ocean; NRCS; Doppler spectrum; azimuthal ambiguity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Meng, H.; Wang, X.; Chong, J.; Wei, X.; Kong, W. Doppler Spectrum-Based NRCS Estimation Method for Low-Scattering Areas in Ocean SAR Images. Remote Sens. 2017, 9, 219.

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