Hybrid Polarimetric GPR Calibration and Elongated Object Orientation Estimation
20 May 2019-IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (IEEE)-Vol. 12, Iss: 7, pp 2080-2087
TL;DR: It is concluded that radar polarimetry can provide not only richer information than single-polarization GPR, but also a reliable approach for orientation estimation of a subsurface elongated object.
Abstract: Ground penetrating radar (GPR) has been widely applied to the detection of subsurface elongated targets, such as underground pipes, concrete rebars, and subsurface fractures. The orientation angle of a subsurface elongated target can hardly be delineated by a commercial single-polarization GPR system. In this paper, a hybrid dual-polarimetric GPR system, which consists of a circularly polarized transmitting antenna and two linearly polarized receiving antenna, is employed to detect buried elongated objects. A polarimetric calibration experiment using a gridded trihedral is carried out to correct the imbalances and cross talk between the two receiving channels. A full-polarimetric scattering matrix is extracted from the double-channel GPR signals reflected from a buried elongated object. An improved Alford rotation method is proposed to estimate the orientation angle of the elongated object from the extracted scattering matrix, and its accuracy is validated by a numerical test. A laboratory experiment was further conducted to detect five metal rebar buried in dry sand at different orientation angle relative to the GPR scan direction. The maximum relative error of the estimated angles of the buried rebars in the migrated GPR images is less than 5%. It is concluded that radar polarimetry can provide not only richer information than single-polarization GPR, but also a reliable approach for orientation estimation of a subsurface elongated object.
Citations
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TL;DR: An automatic detection and localization method using deep learning and migration to identify regions of interest containing hyperbolas in a GPR image and locate the rebar.
86 citations
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Abstract: The deep convolutional neural network (DeCNN) is considered one of promising techniques for classifying the high-spatial-resolution remote sensing (HSRRS) scenes, due to its powerful feature extraction capabilities. It is well-known that huge high-quality labeled datasets are required for achieving the better classification performances and preventing overfitting, during the training DeCNN model process. However, the lack of high-quality datasets limits the applications of DeCNN. In order to solve this problem, in this article, we propose a HSRRS image scene classification method using transfer learning and the DeCNN (TL-DeCNN) model in a few shot HSRRS scene samples. Specifically, three typical DeCNNs of VGG19, ResNet50, and InceptionV3, trained on the ImageNet2015, the weights of their convolutional layer for that of the TL-DeCNN are transferred, respectively. Then, TL-DeCNN just needs to fine-tune its classification module on the few shot HSRRS scene samples in a few epochs. Experimental results indicate that our proposed TL-DeCNN method provides absolute dominance results without overfitting, when compared with the VGG19, ResNet50, and InceptionV3, directly trained on the few shot samples.
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TL;DR: In this paper , a hybrid-polarization ground penetrating radar (GPR) system is proposed for detecting and evaluation of rebar corrosion, which can record rebar reflections in two orthogonal polarimetric channels.
23 citations
TL;DR: In this article, an ultrasonic imaging method is proposed for inspecting the grouted splice sleeves in precast concrete (PC) structures using reverse time migration (RTM) algorithm based on an elastic wave equation.
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TL;DR: A low cutoff frequency is recommended for selecting a GPR antenna with an appropriate nominal frequency when it is used in the detection of an anomaly inside and behind a reinforced concrete structure, in which the spacing of the rebar net is known.
Abstract: Ground-penetrating radar (GPR) has been widely applied to the nondestructive inspection of concrete structures such as tunnel lining, bridge deck, and retaining wall, which are usually reinforced by steel bars. The scattering of electromagnetic (EM) waves caused by the dense steel rebar embedded in the concrete structures has a severe influence on the penetration capacity of GPR waves. In this letter, the scattering and penetration characteristics of EM waves propagating through rebar net are investigated via both numerical and laboratory experiments, with an aim to select the antenna nominal frequency for a different reinforcement density. The results show that the rebar, which is perpendicular to the polarization direction of GPR waves and has a very small diameter compared with the wavelength, is almost transparent to the impinged GPR waves. The scattering and interaction of GPR waves caused by the rebar that is parallel to the polarization direction result in a shielding effect, which is manifested as a blind band in the low-frequency range in the transmitted spectrum. This result violates the rule of thumb commonly used in the GPR community, i.e., the lower frequency has a deeper GPR penetration depth. In the end, a low cutoff frequency is recommended for selecting a GPR antenna with an appropriate nominal frequency when it is used in the detection of an anomaly inside and behind a reinforced concrete structure, in which the spacing of the rebar net is known.
18 citations
Cites background from "Hybrid Polarimetric GPR Calibration..."
...It is known that the scattering signal is sensitive to the relative angle between the rebar orientation and the polarization direction of the EM waves [21], [22]....
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References
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446 citations
"Hybrid Polarimetric GPR Calibration..." refers methods in this paper
...The Alford rotation transformation [24] is applied to the ex-...
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TL;DR: In this article, a technique that uses the radar return from natural targets and at least one trihedral corner reflector to calibrate compressed polarimetric radar data is described, which is based on the theoretical result that for natural targets with azimuthal symmetry the copolarized and crosspolarized components of the scattering matrix are uncorrelated.
Abstract: A technique that uses the radar return from natural targets and at least one trihedral corner reflector to calibrate compressed polarimetric radar data is described. Calibration for relative amplitude, relative phase, absolute amplitude, and system crosstalk is addressed. The crosstalk calibration method is based on the theoretical result that for natural targets with azimuthal symmetry the copolarized and crosspolarized components of the scattering matrix are uncorrelated, and the method does not require any external calibration targets to be deployed before imaging. Because compressed data are used, one is forced to model the transmitting and receiving systems as reciprocal. Even though the inferred transmit and receive matrices are not each simply related to the physical transmitter and receiver, the true Stokes matrix for each pixel in an image can be accurately determined by this approach. The method is illustrated by estimating the crosstalk parameters of the NASA/JPL aircraft for different types of terrain and for two frequencies. For the C-band system, the crosstalk is less than -20 dB for all ranges in the images. The crosstalk of the L-band system is a function of range, however, and may be as poor as -10 dB in the near range, leading to a noticeable distortion of the polarization signatures. >
389 citations
TL;DR: An ultrawide-bandwidth (UWB) ground penetrating radar (GPR) was used to collect fully-polarimetric backscattered data from 10 to 800 MHz using a dual-Polarization version of the previously developed dielectric-loaded horn-fed bow-tie (HFB) antenna to discriminate subsurface ordnance from false-alarm objects that do not have elongated bodies.
Abstract: An ultrawide-bandwidth (UWB) ground penetrating radar (GPR) was used to collect fully-polarimetric backscattered data from 10 to 800 MHz using a dual-polarization version of the previously developed dielectric-loaded horn-fed bow-tie (HFB) antenna. Special processing algorithms were developed to extract the polarization, orientation, depth, and length features of the target under investigation. The polarization and resonance features were utilized to discriminate subsurface ordnance from false-alarm objects that do not have elongated bodies. The classification of a specific type of unexploded ordnance (UXO) was also performed using the known length information. The processed results obtained from an initial blind field test show a very encouraging discrimination performance.
134 citations
"Hybrid Polarimetric GPR Calibration..." refers background in this paper
...Full polarimetric GPR systems, which enable the measurement of the four components of the polarimetric scattering matrix, have also been developed for subsurface target detection [6], [11]....
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...The linearity factor estimated from the eigenvalues of the scattering matrix can be used to classify rotationally symmetric and elongated objects [11], [15]....
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TL;DR: The backscattered fields from cylinders may be strongly depolarized depending on the orientation of cylinders relative to the antennas, the electrical properties of the cylinders, and the radius of the cylinder compared to the incident wavelength.
124 citations
"Hybrid Polarimetric GPR Calibration..." refers background or methods in this paper
...Full polarimetric GPR systems, which enable the measurement of the four components of the polarimetric scattering matrix, have also been developed for subsurface target detection [6], [11]....
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...When the diameter of a subsurface cylinder is larger than the nominal wavelength of GPR, the depolarization capacity of the cylinder is decreased [6] and the orientation estimation method may be...
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...to its orientation direction with respect to the polarization direction of the transmitting and receiving antennas [5], [6]....
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TL;DR: An ESPRIT-based algorithm is proposed to estimate the azimuth and elevation angles of multiple independent sources using cumulants and imposes no geometric constraint on the array.
Abstract: An ESPRIT-based algorithm is proposed to estimate the azimuth and elevation angles of multiple independent sources. The algorithm uses cumulants and imposes no geometric constraint on the array. Only one third of the hardware is needed for our algorithm as compared with covariance-based two-dimensional (2-D) ESPRIT. Our algorithm can estimate azimuth and elevation angles of M-1 sources using M sensors. Simulation results show that for several array configurations, our algorithm works well.
109 citations
"Hybrid Polarimetric GPR Calibration..." refers background in this paper
...The orientation of a subsurface elongated object can be readily estimated from multiple parallel GPR profiles recorded on ground surface [14]....
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