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This paper proposes a probabilistic framework for assessing the condition of structural concrete with respect to moisture contained within cured concrete using a 10 GHz synthetic aperture radar (SAR) imaging system. Functional relationships between integrated SAR amplitude (SAR image index) and moisture content have been developed in previous studies utilizing experimental data collected in a controlled laboratory environment. These studies have shown that the integrated SAR amplitude (SAR image index) increases exponentially with an increase in moisture content at a given water-to-cement (w/c) ratio. In this study, a reliability model is developed using the integrated SAR amplitude and moisture content relationships from an experimental study which included concrete specimens with five different w/c ratios in addition to variations of critical functional parameters and Monte Carlo simulation techniques. The reliability model of moisture content detected with synthetic aperture radar in this study follows a normal distribution. An illustrative example is presented to demonstrate the reliability-based methods of measuring in-place moisture content using an integrated SAR amplitude. The findings from this study emphasize the need to consider the variation of parameters affecting nondestructive SAR imaging results for the purposes of diagnosing moisture content of aged structural concrete. [ABSTRACT FROM AUTHOR]

Change detection for synthetic aperture radar (SAR) images is a key process in many applications exploiting remote-sensing images. It is a challenging task due to the presence of speckle noise in SAR imaging. This article investigates the problem of change detection in multitemporal SAR images. Our motivation is to avoid using only one detector to measure the change level of different features which is usually considered by classical methods. In this article, we propose an unsupervised change detection approach based on frequency difference in wavelet domain and a modified fuzzy c-means (FCM) clustering algorithm. First, the proposed method extracts high-frequency and low-frequency components using wavelet transform, and then constructs highfrequency and low-frequency difference images using different detectors. Finally, inverse wavelet transform is carried out to obtain the final difference image. In addition, inspired by manifold structure constraint, we incorporate weighted local information into the FCM to reduce the influence of speckle noise. Experimental results performed on simulated and real SAR images show the effectiveness of the proposed method, in terms of detection performance, compared with the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

In shipborne inverse synthetic aperture radar (ISAR), not only the target, but also the radar ship will have nonstationary 3-dimensional rotations induced by the irregular sea wave. Thus, how to compensate the radar ship’s rotations is the key problem in reconstructing the shipborne ISAR image of ship target successfully. In this letter, a novel received signal model of shipborne ISAR is proposed. On the basis of the proposed model, the Doppler frequency induced by the rotations of the target and the radar ship can be separated from the received signal, individually. An analysis of the effects of the radar ship’s rotations on the obtained image is given. Error analysis and imaging simulation are done and the results verified the correctness of the proposed model and the effects of the radar ship’s rotations. [ABSTRACT FROM AUTHOR]

Differential Interferometric Synthetic Aperture Radar (DInSAR) is an increasingly viable method for assessing permafrost terrain stability, but the accuracy and performance within discontinuous permafrost terrain has not been well studied. We used a RADARSAT-2 DInSAR data stack for a 120-day period in the summer of 2010 to map seasonal surface displacement in the discontinuous permafrost terrain of Yellowknife, Northwest Territories. Calculated displacement was compared to surficial geology and municipal land use zones. Displacement results reveal that glaciofluvial, glaciolacustrine, humanly modified, and organic terrain are increasingly unstable, in contrast to predominantly stable bedrock. Within municipal zones, increased proportional displacement is related to higher proportions of glaciolacustrine sediments and organic terrain. Organic terrain, associated with the highest proportion of the moderate downward displacement (-3.0 cm to -6.0 cm), occupies less than 6% of the total area. Widespread glaciolacustrine sediments (30% total area) are associated with most of the downward displacement in municipal zones. Semi-quantitative field and geotechnical validations indicate that most areas of moderate seasonal downward displacement in developed areas also represent areas of long-term subsidence. This work shows that even a short InSAR data stack and a simple stack processing method can yield information that is useful for municipal knowledge and planning. [ABSTRACT FROM AUTHOR]

Monitoring deformation of linear infrastructures such as expressway and railway caused by natural processes or anthropogenic activities is a vital task to ensure the safety of human lives and properties. Interferometric Synthetic Aperture Radar (InSAR) has been widely recognized as an effective technology to carry out large-area surface deformation mapping. However, its application in linear infrastructure deformation monitoring has not been intensively studied till now. In this article, a modified Small BAseline Subset (SBAS) method is proposed to retrieve the deformation patterns of the expressway. In our method, only the point-like targets identified on the expressway were kept in our analysis, and two complementary subsets of interferograms were formed to better separate the signals of height error and deformation from inteferometric phase observations. We successfully applied this method with multitemporal high-resolution TerraSAR-X images to retrieve the spatial-temporal pattern of surface deformation along the Bei’an-Heihe expressway that is located in island-permafrost areas and threatened by geohazards. [ABSTRACT FROM AUTHOR]

A synthetic aperture is an effective approach to enhancement of the resolution of telescopes. In this paper, a new method to improve the resolution by using a pair of gratings is proposed. It allows collection of parts of the light diffracted from the object which could not previously reach the imaging device. This method improves the resolution and light energy utilization ratio of telescopes without introducing new chromatic aberration. An experiment for resolution testing was carried out and the feasibility and availability of the method were verified. [ABSTRACT FROM PUBLISHER]

Phase unwrapping arises as a key step in several imaging technologies, from which we emphasize interferometric synthetic aperture radar (InSAR), synthetic aperture sonar, magnetic resonance imaging. Due to various decorrelation factors, such as spatial, temporal, spectral, thermal noise, and so on, there is much phase noise in InSAR interferogram. The phase noise degrades the visual quality of the interferogram, increases the errors of the results derived from the InSAR interferogram, and obstructs the phase unwrapping. In addition to accuracy, computational efficiency is very important. recurrent phase unwrapping method appears to be one of the most computational efficient methods proposed for this problem. However, its beaver in presence of noise is unknown. In this paper, one-dimensional (1-D) recurrent phase unwrapping algorithm is used to eliminate phase discontinuities in N-dimensional (N-D) complex arrays. The behavior of this method in the presence of different noise levels is studied and the problem of phase filtration and its effect on recurrent algorithm behavior is considered. Tests of the method presented illustrate the validity and effectiveness of proposed algorithm for difficult problems with noisy and discontinuous original phases. [ABSTRACT FROM AUTHOR]

A Japanese Earth Resources Satellite (JERS)-1 L-band synthetic aperture radar (SAR) dataset was used for estimating topsoil thickness, of different types, in arid and semi-arid areas in north-eastern Jordan. In this research, the relationship between remotely sensed data, backscattering coefficient and the thickness of topsoil was investigated. Based on the dielectric constant properties of the topsoil samples, the relationship between the backscattering coefficient and the topsoil thickness was obtained by developing a multilayer modelling analysis. Using this model, the topsoil thickness had been estimated by means of the derived backscattering coefficients from JERS-1 SAR image. The estimated thickness values of the different topsoil types were found to be comparable with field ground data. The estimated minimum thickness for hardpan topsoil is 55 cm; Qaa topsoil, 74 cm; and topsoil of herbaceous area, 46 cm, while the estimated maximum thickness is more than 98 cm, more than 100 cm, and 82 cm, respectively. Ground data, on the other hand, revealed the minimum thickness for hardpan topsoil to be 50 cm; Qaa topsoil, 70 cm; and topsoil of herbaceous area, 40 cm, while the maximum thickness is more than 120 cm, more than 100 cm, and 80 cm, respectively. [ABSTRACT FROM AUTHOR]

A generalized mathematical procedure is presented for investigating the electromagnetic response characteristics of multiple cylindrically curved thin screens excited by a line electric current source, and the mathematical treatment is based on the direct integral equation technique combined with Galerkin's procedure. Both the near- and the far-zone field solutions to such a multiple coupling system are obtained in an analytical form, and the induced electric currents on the curved thin screens are expanded in terms of a series of Chebyshev polynomials of the first kind. Furthermore, parametric studies are performed to show the variation of the penetrated near-zone and scattered far-zone fields of some typical cylindrically curved thin screens. [ABSTRACT FROM AUTHOR]