Burst mode to strip-map mode SAR interferometry of ALOS PALSAR

A complete processing flow is proposed to implement burst mode to strip-map mode interferometry for ALOS PALSAR data. The processing flow is applied to an interferometric pair comprised of FBD (High Resolution mode [Dual polarization], belonging to strip-map mode) and WB1 (Wide observation mode, belonging to burst mode) mode of PALSAR. Interferometric products including differential interferometric phase and DEM are generated. The evaluation of these products shows satisfactory precision.Geosciences, MultidisciplinaryRemote SensingCPCI-S(ISTP)

Stick-slip meta-instability of coal under uniaxial loading and AE and EMR response characteristics

Meta-instability stage is the most abundant precursory information and the most intense change stage in the process of fault stick-slip instability. In order to deeply explore the characteristics of coal meta-instability and the response law of acoustic and electrical signals in this process, the uniaxial graded loading experiments of coal samples with different prefabricated crack angles were carried out. The internal fracture source location, surface displacement field, acoustic emission and electromagnetic radiation signals of the samples were synchronously collected, and the mechanical behavior and acoustic and electrical characteristics of coal meta-instability were analyzed. The results show that: ① The inclination angle of the prefabricated crack significantly affects the internal stress distribution of the loaded coal sample, and even the expansion distribution of the new cracks in the meta-instability stage. The acoustic emission count and energy have obvious responses to stress and failure. When the meta-instability is near, the acoustic emission count and energy increase sharply at the same time, and the signal proportion is close to 20%. The response characteristics can be used as the basis for judging the crack coal sample entering the meta-instability stage. ② After entering the meta-instability state, the electromagnetic radiation activity is the most intense, which is almost consistent with the occurrence time of stress drop. Before the main fracture occurs, the energy and amplitude of electromagnetic radiation increase sharply, and the peak energy increases first and then decreases with the increase of crack dip angle. When the crack dip angle is 45°, the electromagnetic radiation count accounts for the largest proportion of the total instability process. ③ The fracture profile of the coal sample in the meta-instability stage has been basically formed. The inclination angle of the prefabricated crack has a significant impact on the duration of the meta-instability stage of the coal sample. When the inclination angle is 45°, the duration of the meta-instability stage is the longest, and when the inclination angle is 60°, the duration proportion is the shortest. The research results can be used to formulate the monitoring scheme of fault meta-instability, and the evolution and disaster of large-scale rock burst in fault structural are

Multi-mode SAR Interferometry Processing Research and Implementation

Current operation mode of SAR can be roughly divided into two types: strip-map mode and burst mode. The most conventional mode is strip-map mode, in which the swath width is quite limited. The other type is burst mode, which is an active option to overcome this limitation by cyclically scanning several subswaths, known as ScanSAR. In addition, Envisat ASAR has another type of burst mode, that is, Alternating Polarization mode. ALOS PALSAR and Radarsat-1 also have their own ScanSAR operation modes, but each of them is distinctive from the others in implementation. Numerous theoretical results and applications of interferometry using strip-map data have been published before. Interferometry with burst mode data, however, is much rarer and different from the case of the traditional strip-map mode from raw data focusing to interferogram generation because of its burst nature of data acquisition pattern. In our study, we put our emphasis on each kind of burst mode interferometry and mixed mode interferometry. Until now, our successful research work includes Envisat ASAR WS-WS, IM-WS and ALOS PALSAR WB1-WB1 Interferometry. Other development activities including Envisat AP-AP and Radarsat-1 SNA-SNA interferometry are still on going. In the following paper, we will present our results and give an overview of multi-mode SAR. interferometry for the present spaceborne SAR sensors.Engineering, Electrical & ElectronicPhysics, AppliedEICPCI-S(ISTP)

Advances on the investigation of landslides by space-borne synthetic aperture radar interferometry

Landslides are destructive geohazards to people and infrastructure, resulting in hundreds of deaths and billions of dollars of damage every year. Therefore, mapping the rate of deformation of such geohazards and understanding their mechanics is of paramount importance to mitigate the resulting impacts and properly manage the associated risks. In this paper, the main outcomes relevant to the joint European Space Agency (ESA) and the Chinese Ministry of Science and Technology (MOST) Dragon-5 initiative cooperation project ID 59,339 “Earth observation for seismic hazard assessment and landslide early warning system” are reported. The primary goals of the project are to further develop advanced SAR/InSAR and optical techniques to investigate seismic hazards and risks, detect potential landslides in wide regions, and demonstrate EO-based landslide early warning system over selected landslides. This work only focuses on the landslide hazard content of the project, and thus, in order to achieve these objectives, the following tasks were developed up to now: a) a procedure for phase unwrapping errors and tropospheric delay correction; b) an improvement of a cross-platform SAR offset tracking method for the retrieval of long-term ground displacements; c) the application of polarimetric SAR interferometry (PolInSAR) to increase the number and quality of monitoring points in landslide-prone areas; d) the semiautomatic mapping and preliminary classification of active displacement areas on wide regions; e) the modeling and identification of landslides in order to identify triggering factors or predict future displacements; and f) the application of an InSAR-based landslide early warning system on a selected site. The achieved results, which mainly focus on specific sensitive regions, provide essential assets for planning present and future scientific activities devoted to identifying, mapping, characterizing, monitoring and predicting landslides, as well as for the implementation of early warning systems.This work was supported by the ESA-MOST China DRAGON-5 project with ref. 59339, by the Spanish Ministry of Science and Innovation, the State Agency of Research (AEI), and the European Funds for Regional Development under grant [grant number PID2020-117303GB-C22], by the Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital in the framework of the project CIAICO/2021/335, by the Natural Science Foundation of China [grant numbers 41874005 and 41929001], the Fundamental Research Funds for the Central University [grant numbers 300102269712 and 300102269303], and China Geological Survey Project [grant numbers DD20190637 and DD20190647]. Xiaojie Liu and Liuru Hu have been funded by Chinese Scholarship Council Grants Ref. [grant number 202006560031] and [grant number 202004180062], respectively

Risk assessment of heavy metals in soils contaminated by smelting waste for the perspective of chemical fraction and spatial distribution

The heavy metals contamination in soil has attracted increasing attention. In this study, the main objective was to determine three heavy metals (Cd, Pb, and Cr) of soils contaminated by smelting waste, and to evaluate pollution risk. The Pb (15.48 mg/kg) and Cd (311.39 mg/kg) mean concentrations exceeded the national standard, while Cr (48.60 mg/kg) concentration did not exceed. The Heavy metal fractions analysis showed that three heavy metals were dominated by FeMn oxides fraction (Fe-Mn). The correlation and cluster analysis indicated that there was significant correlation between Cd and Pb (0.55< r < 0.96), while Cr was not correlation to Cd and Pb. The environmental pollution of heavy metals was assessed by the ratio of secondary phase and primary phase (RSP). The result showed that RSP values of Cd, Pb, and Cr range from 13.05–54.28, 16.11–4.97 and 1.61–52.33, which indicated soil was serious contaminated by them. These results showed that smelting waste discharge led to this smelter soil being seriously contaminated by multiple heavy metals which have a tendency to transport and accumulate into deep soil due to their high fractional transformation

Research on the Creep Model of Deep Coal Roadway and Its Numerical Simulation Reproduction

The long-term stability of coal mine roadway engineering is critical to the safe mining of coal resources and the protection of the surface environment. In this paper, the creep test of coal samples in coal roadway was carried out by multi-stage constant load method, and the test results showed that when the stress level was low, the creep curve had a attenuated stage and a steady-state stage, and the steady-state creep rate tended to increase with the increase in the stress level; When the stress level was higher than the yield stress, the creep rate curve appeared to have an acceleration stage after the steady-state stage. The instability failure mode of the coal sample was mainly shear failure with local tension failure. For this, a New Fractional-order Nonlinear Viscoelastic-plastic Rheological Model (NFNVRM) was established by introducing Abel elements and Nonlinear elements, and the constitutive equation of the model was deduced. The new model can fully reflect the stable decay stage and accelerated rheological stages of coal samples, and the parameter identification curve was consistent with the experimental results, which verifies the correctness and reasonableness of the NFNVRM. Meanwhile, based on the FLAC3D secondary development interface, the constitutive equations of the NFNVRM were written into the software to obtain new Dynamic Link Library (DLL) files. The simulation results were consistent with the experimental results when the DLL file was called. Finally, the NFNVRM.dll was applied to predict the surrounding rock deformation of an S mine. The study&rsquo;s findings offer suggestions for environmental protection

An Adaptive Decomposition Approach with Dipole Aggregation Model for Polarimetric SAR Data

Polarimetric synthetic aperture radar (PolSAR) has attracted lots of attention from remote sensing scientists because of its various advantages, e.g., all-weather, all-time, penetrating capability, and multi-polarimetry. The three-component scattering model proposed by Freeman and Durden (FDD) has bridged the data and observed target with physical scattering model, whose simplicity and practicality have advanced remote sensing applications. However, the three-component scattering model also has some disadvantages, such as negative powers and a scattering model unfitted to observed target, which can be improved by adaptive methods. In this paper, we propose a novel adaptive decomposition approach in which we established a dipole aggregation model to fit every pixel in PolSAR image to an independent volume scattering mechanism, resulting in a reduction of negative powers and an improved adaptive capability of decomposition models. Compared with existing adaptive methods, the proposed approach is fast because it does not utilize any time-consuming algorithm of iterative optimization, is simple because it does not complicate the original three-component scattering model, and is clear for each model being fitted to explicit physical meaning, i.e., the determined adaptive parameter responds to the scattering mechanism of observed target. The simulation results indicated that this novel approach reduced the possibility of the occurrence of negative powers. The experiments on ALOS-2 and RADARSAT-2 PolSAR images showed that the increasing of adaptive parameter reflected more effective scatterers aggregating at the 45° direction corresponding to high cross-polarized property, which always appeared in the 45° oriented buildings. Moreover, the random volume scattering model used in the FDD could be expressed by the novel dipole aggregation model with an adaptive parameter equal to one that always appeared in the forest area