Complex Permittivity and Penetration Depth Estimation from Airborne P-Band SAR Data Applying a Hybrid Decomposition Method

Author(s):  
Anke Fluhrer ◽  
Thomas Jagdhuher ◽  
Alireza Tabatabaeenejad ◽  
Hamed Alemohammad ◽  
Carsten Montzka ◽  
...  
2019 ◽  
Vol 147 ◽  
pp. 232-241 ◽  
Author(s):  
Michael Schlund ◽  
Daniel Baron ◽  
Paul Magdon ◽  
Stefan Erasmi

1997 ◽  
Vol 119 (4) ◽  
pp. 791-801 ◽  
Author(s):  
Jay F. Tu ◽  
Kishore N. Lankalapalli ◽  
Mark Gartner ◽  
Keng H. Leong

High-power CO2 laser welding has been widely used in the industry because of its high productivity and excellent weld quality. In order to tap the potential of this process completely, it is important to have on-line weld quality inspection methods to improve the process productivity and reliability by achieving 100 percent weld inspection. Weld penetration is one of the most important factors critical to the quality of a laser weld. However, it is very difficult to directly measure the extent of penetration without sectioning the workpiece. In this paper a model-based penetration depth estimation technique suitable for the production environment is developed. The proposed model relates the temperature measured on the bottom surface of the workpiece, weld bead width, laser beam power and welding speed to penetration depth. The closed-loop depth estimator combines the model and a model-error compensator to compensate for the uncertainty in the measurement of the laser power and absorptivity. Other effects considered are the averaging due to the finite size of the sensor, delay based on the sensor location and the process and sensor dynamics. Several bead-on-plate and butt welds were made on low carbon steel plates to validate the static process models and the depth estimation scheme. Temperatures on the bottom surface of the workpiece during welding were measured using infrared thermocouples. The welds were sectioned longitudinally to obtain the penetration profile. The penetration profiles estimated by the depth estimator matched satisfactorily with the measured penetration profiles. The results validate the capability of the proposed depth estimator to estimate penetration depth and its ability to trace the dynamic changes in penetration depth.


Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 72
Author(s):  
Stanisława Porzycka-Strzelczyk ◽  
Jacek Strzelczyk ◽  
Kamil Szostek ◽  
Maciej Dwornik ◽  
Andrzej Leśniak ◽  
...  

The main goal of this research was to propose a new method of polarimetric SAR data decomposition that will extract additional polarimetric information from the Synthetic Aperture Radar (SAR) images compared to other existing decomposition methods. Most of the current decomposition methods are based on scattering, covariance or coherence matrices describing the radar wave-scattering phenomenon represented in a single pixel of an SAR image. A lot of different decomposition methods have been proposed up to now, but the problem is still open since it has no unique solution. In this research, a new polarimetric decomposition method is proposed that is based on polarimetric signature matrices. Such matrices may be used to reveal hidden information about the image target. Since polarimetric signatures (size 18 × 9) are much larger than scattering (size 2 × 2), covariance (size 3 × 3 or 4 × 4) or coherence (size 3 × 3 or 4 × 4) matrices, it was essential to use appropriate computational tools to calculate the results of the proposed decomposition method within an acceptable time frame. In order to estimate the effectiveness of the presented method, the obtained results were compared with the outcomes of another method of decomposition (Arii decomposition). The conducted research showed that the proposed solution, compared with Arii decomposition, does not overestimate the volume-scattering component in built-up areas and clearly separates objects within the mixed-up areas, where both building, vegetation and surfaces occur.


2015 ◽  
Vol 69 (1) ◽  
pp. 113-126 ◽  
Author(s):  
Xiaolin Bian ◽  
Yun Shao ◽  
Wei Tian ◽  
Chunyan Zhang

This paper presents a shallow water depth estimation methodology using S-band Synthetic Aperture Radar (SAR) data from the HJ-1C satellite. It is based on the shoaling and refraction of long surface gravity waves as they propagate shoreward. A two-scale Bragg scattering model is used to describe the imaging process of long waves by SAR. By computing the Fast Fourier Transformation (FFT) for the selected sub image, wavelength and direction of the long wave can be retrieved from the two-dimensional (2D) spectra with wave tracking technology. Shallow water depths are then obtained from the linear dispersion relation with the calculated angular wave frequency obtained from other sources or first guesses of initial water depths or wave periods. Applicability and effectiveness are tested in the near-shore area of the Fujian province, China. Comparison between the derived results and water depths from an Electronic Navigational Chart (ENC) indicates that HJ-1C SAR is capable of higher resolution underwater topography detection, and the methodology can be used for shallow water depth estimation with good accuracy. The average absolute error and average relative error of the estimated results is 0·86 m and 11·05%, respectively.


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