| 1. |
- Ramos, Lucas P., et al.
(author)
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A wavelength-resolution sar change detection method based on image stack through robust principal component analysis
- 2021
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In: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:5, s. 1-16
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Journal article (peer-reviewed)abstract
- Recently, it was demonstrated that low-frequency wavelength-resolution synthetic aperture radar (SAR) images could be considered to follow an additive mixing model due to their backscatter characteristics. This simplification allows for the use of source separation methods, such as robust principal component analysis (RPCA) via principal component pursuit (PCP), for detecting changes in those images. In this manuscript, a change detection method for wavelength-resolution SAR images based on image stack through RPCA is proposed. The method aims to explore both the temporal and flight heading diversity of a set of wavelength-resolution multitemporal SAR images in order to detect concealed targets in forestry areas. A heuristic based on three rules for better exploring the RPCA results is introduced, and a new configurable parameter for false alarm reduction based on the analysis of image windows is proposed. The method is evaluated using real data obtained from measurements of the ultrawideband (UWB) very high-frequency (VHF) SAR system CARABAS-II. Experiments for stacks of four and seven reference images are conducted, and the use of reference images acquired with different flight headings is explored. The results indicate that a gain in performance can be achieved by using large image stacks containing, at least, one image of each possible flight heading of the data set, which can result in a probability of detection (PD) above 99% for a false alarm rate (FAR) as low as one false alarm per three square kilometers. Furthermore, it is demonstrated that high PD and low FAR can be achieved, also considering images from similar flight headings as reference images. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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| 2. |
- Voigt, Gustavo H. M., et al.
(author)
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Change detection method for intensity VHF wavelength-resolution SAR images
- 2021
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510645684
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Conference paper (peer-reviewed)abstract
- This paper presents the proposal of a new change detection method for intensity VHF wavelength-resolution images. High-Amplitude pixels are related to the presence of strong scatterers, resulting in high detection probability performance. However, the number of false alarms tends to be high too. In this initial study, difference images are considered to reduce the influence of the strong scatterers that are not related to targets, i.e., present in both surveillance and reference images. The proposed change detection method is based on a likelihood-ratio test, where the tested hypothesis is the bivariate exponential distribution. The derivation of the proposed likelihood test is presented. Finally, the proposed change detection method is assessed considering data measured with the CARABAS II VHF UWB SAR system. Preliminary results show that the proposed method is efficient in detecting positive changes. © 2021 SPIE.
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| 3. |
- Vu, Viet Thuy, 1977-, et al.
(author)
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Changing flight heading during pass to enhance SAR change detection performance
- 2021
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In: IET radar, sonar & navigation. - : John Wiley and Sons Inc. - 1751-8784 .- 1751-8792. ; 15:8, s. 817-826
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Journal article (peer-reviewed)abstract
- Due to the wavelength-resolution characteristics, wavelength-resolution synthetic aperture radar (SAR) is considered for the change detection application aiming to achieve high detection probability and low false alarm rate. However, wavelength-resolution SAR change detection suffers from the problems caused by specular reflection of the elongated structure in the SAR scene, the dependency of radar cross-section on incident angle of electromagnetic wave, the interference due to antenna backlobe and so forth. Hardware and software solutions are therefore desired to deal with these problems. The authors propose to change flight heading during passes as a natural solution. The proposed solution is tested with the CARABAS data using a typical SAR change detection method. The achieved change detection results show the good performance of the proposed solution, for example, the detection probability is up to 100% with the false alarm rate of 0.5 per square kilometre. © 2021 The Authors. IET Radar, Sonar & Navigation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
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