Abstract
Ground-based synthetic aperture radar (GB-SAR) is a relatively new technique that can be used to monitor the deformation of large-volume targets, such as dams, slopes, and bridges. In this study, the permanent scatterer (PS) technique is used to address the issues encountered in the continuous monitoring of the external deformation of an arch-gravity dam in a hydraulic and hydropower engineering structure in Hubei, China; the technique includes large image data sizes, high accuracy requirements, a susceptibility of the monitoring data to atmospheric disturbances, complex phase unwrapping, and pronounced decoherence. Through an in-depth investigation of PS extraction methods, a combined PS selection (CPSS) method is proposed by fully taking advantage of the signal amplitude and phase information in the monitored scene. The principle and implementation of CPSS are primarily studied. In addition, preliminarily selected PS candidates are directly used to construct and update a triangular irregular network (TIN) to maintain the stability of the subsequent Delaunay TIN. To implement this method, a differential-phase standard-deviation threshold method is proposed to extract PSs that are highly spatially coherent and consistent. Finally, the proposed CPSS was applied to the safety monitoring of the dam. The monitoring results are compared with conventional inverted plumb line monitoring results, and the proposed CPSS is found to be effective and reliable.
Highlights
A differentialphase standard-deviation threshold method is proposed to extract highly spatially coherent and consistent permanent scatterer (PS). (3) e proposed method was applied to the safety monitoring of a dam, and the monitoring results are compared with those the inverted plumb line monitoring method. e comparison demonstrates that the combined PS selection (CPSS) method is effective and reliable
A new method (i.e., CPSS) for identifying and extracting PSs is proposed considering the characteristics of GB-synthetic aperture radar (SAR) data processing, including large image data sizes, high accuracy requirements, a high susceptibility of the monitoring data to atmospheric disturbances, complex phase unwrapping, and pronounced decoherence. e principle and implementation of the proposed method are investigated in detail. is method was applied to the safety monitoring of an archgravity dam in a hydraulic and hydropower engineering structure in Hubei, China
By comparing the results obtained using the combined method with inverted plumb line monitoring data, the effectiveness and reliability of the combined method are analysed. e contents and conclusions of this study are summarized as follows: (1) e principle, implementation, and specific steps of the CPSS method were investigated in detail
Summary
In the early twenty-first century, the Italian researchers Ferreti et al proposed a permanent scatterer (PS) technique for satellite-borne synthetic aperture radar (SAR) systems [1,2,3,4] that is an SAR displacement monitoring data processing technique [5,6,7]. is technique extracts targets with a stable phase and extremely high backscattering capacity (i.e., PSs) from long-time-series radar data using a statistical filter, and by modelling and analysing, the PSs obtains various estimated parameters [7]. is technique can significantly reduce the effects of atmospheric phase delays [5] and provides an accurate and reliable approach to estimating the residual phase of landforms. Us, it is necessary to make full use of the properties of PSs to search for a sufficient number of highly temporally and spatially coherent PS point targets and investigate PS extraction methods suitable for GB-SAR data to compensate for the effects of the temporal and spatial decoherence, atmospheric disturbances, and noise on the accurate retrieval of deformation information from GB-SAR data [5, 14,15,16,17,18,19,20] to achieve all-weather, high-accuracy (theoretically of the submillimetre order), and high-resolution displacement monitoring over a large area. In 2015, Zeng et al [47] discussed the use of a combination of a coherence coefficient threshold method (cT) and phase information in the extraction of PSs and used this method to produce a digital elevation model (DEM) from satellite-borne radar data. A differentialphase standard-deviation threshold method is proposed to extract highly spatially coherent and consistent PSs. (3) e proposed method was applied to the safety monitoring of a dam, and the monitoring results are compared with those the inverted plumb line monitoring method. e comparison demonstrates that the CPSS method is effective and reliable
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