Effect of digital elevation models on monitoring slope displacements in open-pit mine by differential interferometry synthetic aperture radar

Displacement monitoring in open-pit mines is one of the important tasks for safe management of mining processes.Differential interferometric synthetic aperture radar(DInSAR),mounted on an artificial satellite,has the potential to be a cost-effective method for monitoring surface displacements over extensive areas,such as open-pit mines.DInSAR requires the ground surface elevation data in the process of its analysis as a digital elevation model(DEM).However,since the topography of the ground surface in open-pit mines changes largely due to excavations,measurement errors can occur due to insufficient information on the elevation of mining areas.In this paper,effect of different elevation models on the accuracy of the displacement monitoring results by DInSAR is investigated at a limestone quarry.In addition,validity of the DInSAR results using an appropriate DEM is examined by comparing them with the results obtained by global positioning system(GPS)monitoring conducted for three years at the same limestone quarry.It is found that the uncertainty of DEMs induces large errors in the displacement monitoring results if the baseline length of the satellites between the master and the slave data is longer than a few hundred meters.Comparing the monitoring results of DInSAR and GPS,the root mean square error(RMSE)of the discrepancy between the two sets of results is less than 10 mm if an appropriate DEM,considering the excavation processes,is used.It is proven that DInSAR can be applied for monitoring the displacements of mine slopes with centimeter-level accuracy.

The 2023 M_(w)6.8 Adassil Earthquake(Chichaoua,Morocco)on a steep reverse fault in the deep crust and its geodynamic implications

The Mw 6.8 Adassil earthquake that occurred in the High Atlas on September 8,2023,was a catastrophic event that provided a rare opportunity to study the mechanics of deep crustal seismicity.This research aimed to decipher the rupture characteristics of the Adassil earthquake by analyzing teleseismic waveform data in conjunction with interferometric synthetic aperture radar(InSAR)observations from both ascending and descending orbits.Our analysis revealed a reverse fault mechanism with a centroid depth of approximately 28 km,exceeding the typical range for crustal earthquakes.This result suggests the presence of cooler temperatures in the lower crust,which facilitates the accumulation of tectonic stress.The earthquake exhibited a steep reverse mechanism,dipping at 70°,accompanied by minor strike-slip motion.Within the geotectonic framework of the High Atlas,known for its volcanic legacy and resulting thermal irregularities,we investigated the potential contributions of these factors to the initiation of the Adassil earthquake.Deep seismicity within the lower crust,away from plate boundaries,calls for extensive research to elucidate its implications for regional seismic hazard assessment.Our findings highlight the critical importance of studying and preparing for significant seismic events in similar geological settings,which would provide valuable insights into regional seismic hazard assessments and geodynamic paradigms.

Analysis of the Quality of Daily DEM Generation with Geosynchronous InSAR

Up-to-date digital elevation model(DEM)products are essential in many fields such as hazards mitigation and urban management.Airborne and low-earth-orbit(LEO)space-borne interferometric synthetic aperture radar(InSAR)has been proven to be a valuable tool for DEM generation.However,given the limitations of cost and satellite repeat cycles,it is difficult to generate or update DEMs very frequently(e.g.,on a daily basis)for a very large area(e.g.,continental scale or greater).Geosynchronous synthetic aperture radar(GEOSAR)satellites fly in geostationary earth orbits,allowing them to observe the same ground area with a very short revisit time(daily or shorter).This offers great potential for the daily DEM generation that is desirable yet thus far impossible with space-borne sensors.In this work,we systematically analyze the quality of daily GEOSAR DEM.The results indicate that the accuracy of a daily GEOSAR DEM is generally much lower than what can be achieved with typical LEO synthetic aperture radar(SAR)sensors;therefore,it is important to develop techniques to mitigate the effects of errors in GEOSAR DEM generation.

Partition of GB-InSAR deformation map based on dynamic time warping and k-means

Ground-based interferometric synthetic aperture radar(GB-InSAR)can take deformation measurement with a high accuracy.Partition of the GB-InSAR deformation map benefits analyzing the deformation state of the monitoring scene better.Existing partition methods rely on labelled datasets or single deformation feature,and they cannot be effectively utilized in GBInSAR applications.This paper proposes an improved partition method of the GB-InSAR deformation map based on dynamic time warping(DTW)and k-means.The DTW similarities between a reference point and all the measurement points are calculated based on their time-series deformations.Then the DTW similarity and cumulative deformation are taken as two partition features.With the k-means algorithm and the score based on multi evaluation indexes,a deformation map can be partitioned into an appropriate number of classes.Experimental datasets of West Copper Mine are processed to validate the effectiveness of the proposed method,whose measurement points are divided into seven classes with a score of 0.3151.

Field testing innovative differential geospatial and photogrammetric monitoring technologiesin mountainous terrain near Ashcroft,British Columbia,Canada

This paper presents a novel approach to continuously monitor very slow-moving translational landslides in mountainous terrain using conventional and experimental differential global navigation satellite system(d-GNSS)technologies.A key research question addressed is whether displacement trends captured by a radio-frequency“mobile”d-GNSS network compare with the spatial and temporal patterns in activity indicated by satellite interferometric synthetic aperture radar(InSAR)and unmanned aerial vehicle(UAV)photogrammetry.Field testing undertaken at Ripley Landslide,near Ashcroft in south-central British Columbia,Canada,demonstrates the applicability of new geospatial technologies to monitoring ground control points(GCPs)and railway infrastructure on a landslide with small and slow annual displacements(<10 cm/yr).Each technique records increased landslide activity and ground displacement in late winter and early spring.During this interval,river and groundwater levels are at their lowest levels,while ground saturation rapidly increases in response to the thawing of surficial earth materials,and the infiltration of snowmelt and runoff occurs by way of deep-penetrating tension cracks at the head scarp and across the main slide body.Research over the last decade provides vital information for government agencies,national railway companies,and other stakeholders to understand geohazard risk,predict landslide movement,improve the safety,security,and resilience of Canada’s transportation infrastructure;and reduce risks to the economy,environment,natural resources,and public safety.

Detecting spatio-temporal urban surface changes using identified temporary coherent scatterers

Synthetic aperture radar(SAR) is able to detect surface changes in urban areas with a short revisit time, showing its capability in disaster assessment and urbanization monitoring.Most presented change detection methods are conducted using couples of SAR amplitude images. However, a prior date of surface change is required to select a feasible image pair. We propose an automatic spatio-temporal change detection method by identifying the temporary coherent scatterers. Based on amplitude time series, χ^(2)-test and iterative single pixel change detection are proposed to identify all step-times: the moments of the surface change. Then the parameters, e.g., deformation velocity and relative height, are estimated and corresponding coherent periods are identified by using interferometric phase time series. With identified temporary coherent scatterers, different types of temporal surface changes can be classified using the location of the coherent periods and spatial significant changes are identified combining point density and F values. The main advantage of our method is automatically detecting spatio-temporal surface changes without prior information. Experimental results by the proposed method show that both appearing and disappearing buildings with their step-times are successfully identified and results by ascending and descending SAR images show a good agreement.

IMPROVED CALIBRATION METHOD FOR AIRBORNE ATI-SAR BASELINE

Airborne Along-Track Interferometric Synthetic Aperture Radar (ATI-SAR) baseline error is a main error resource affecting the precision of velocity measurement of moving objects and therefore should be calibrated externally. The Jet Propulsion Laboratory (JPL) has proposed a calibration scheme for tasks of PacRim98 and PacRim2000 based on several static objects on the ground. In this paper, the influence of phase center uncertainty on baseline determination by using PacRim method proposed by JPL is analyzed. According to the analysis, the phase center uncertainty can cause a constant part of error to the result of baseline calibration. In order to deal with this problem, an improved calibration method on the basis of sensitivity equations and some ground moving targets, whose velocities are already known, is proposed in this paper. The simulation results show that our proposed calibration method has improved the accuracy of baseline calibration and has obviously prohibited the effect of antennas' phase center uncertainty.

INTERFEROGRAM NOISE REDUCTION ALGORITHM BASE ON MAXIMUM A POSTERIORI ESTIMATE

Interferogram noise reduction is a very important processing step in Interferometric Synthetic Aperture Radar(InSAR) technique. The most difficulty for this step is to remove the noises and preserve the fringes simultaneously. To solve the dilemma, a new interferogram noise reduction algorithm based on the Maximum A Posteriori(MAP) estimate is introduced in this paper. The algorithm is solved under the Total Generalized Variation(TGV) minimization assumption, which exploits the phase characteristics up to the second order differentiation. The ideal noise-free phase consisting of piecewise smooth areas is involved in this assumption, which is coincident with the natural terrain. In order to overcome the phase wraparound effect, complex plane filter is utilized in this algorithm. The simulation and real data experiments show the algorithm can reduce the noises effectively and meanwhile preserve the interferogram fringes very well.

基于InSAR技术的中国地表形变一张图研制

地表形变危害巨大且深远,利用合成孔径雷达干涉测量(interferometric synthetic aperture radar,InSAR)技术监测地表形变虽已较为成熟,但是超大范围,甚至全国范围的地表形变快速提取仍充满挑战。为快速获取全国地表形变信息,设计了一种基于超算并行计算的广域地表形变快速提取优化方法,并对干涉集基线组合方法、广域相位解缠算法、大气效应改正方法等进行了改进和创新。基于该方法,采用10157景哨兵1号数据,研制了中国全境2021年度40m分辨率地表形变速率图,经验证形变速率精度为4.82mm/a,有效覆盖度为94.6%,图幅间无明显接边差异。同时对国内典型地表形变区域进行了分析。研究为广域地表形变常态化快速提取提供了参考。

采用PolInSAR技术反演植被高度的算法应用与研究进展

极化合成孔径雷达干涉测量(polarimetric interferometric synthetic aperture radar,PolInSAR)技术是提取植被高度的有效手段,应用其进行植被高度反演已经有20多年的历史。旨在通过分析近年来国内外基于PolInSAR技术的植被高度反演研究的现状,以全面、深入了解当前国际研究动态。

基于时序InSAR的上海市地面沉降时空演变特征分析

基于2018-06—2019-10期间的17景Sentinel-1A影像数据,采用永久散射体合成孔径雷达干涉测量(permanent scatterer interferometric synthetic aperture radar,PS‐InSAR)技术研究了上海市的地面沉降时空演变特征,获得了上海市该时间段内的平均沉降速率场、沉降时间序列及累计沉降量,并分析了该地区的地面沉降时空演变特征与降水量、城市化进程等因素的关联关系。结果表明:①在研究时段内,上海市不均匀沉降明显,沉降最严重的区域位于松江区邱泾村,沉降速率范围为-18.3~-14.2 mm/a;此外,金山区南星桥附近也出现较为明显的沉降现象,最大累计沉降量达-23 mm。②上海市北部出现大范围沉降,地区平均沉降速率在-11~-4 mm/a间。西部及西南部也出现大范围沉降现象,并出现明显的沉降漏斗,沉降较为严重,而东部地区地面呈现抬升现象。③研究区域地面沉降的季节性变化与降水量有关;城市化进程与地面沉降存在一定的空间相关性。

A joint InSAR-GNSS workfow for correction and selection of interferograms to estimate high-resolution interseismic deformations

Knowledge of the spatial distribution of interseismic deformations is essential to better understand earthquake cycles.The existing methods for improving the reliability of the obtained deformations often rely on visual inspection and prior model corrections that are time-consuming,labor-intensive,and do not consider the spatial distribution of interseismic deformations.Interferometric Synthetic Aperture Radar(InSAR)data provides wide-scale coverage for interseismic deformation monitoring over a wide area.However,the interseismic signal featured as millimeter-scale and long-wave deformations is often contaminated with noise.In the present study,a new workfow to correct the interferometric phase and quantitatively select interferograms is proposed to improve the accuracy of interseismic deformation measurements.Initially,the Generic Atmospheric Correction Online Service(GACOS),Intermittent Code for Atmospheric Noise Depression through Iterative Stacking(I-CANDIS),and plate model are combined to correct the atmospheric screen and long-wave ramp phase.Subsequently,the Pearson’s Correlation Coefcient(PCC)between the interferometric phase and the Global Navigation Satellite System(GNSS)constrained interseismic model as well as the STandard Deviation(STD)of the interferometric phase are introduced as criteria to optimize the selection of interferograms.Finally,the intermittent stacking method is used to generate an average velocity map.A comprehensive test using Sentinel-1 images covering the Haiyuan Fault Zone validate the efectiveness of our workfow in measuring interseismic deformations.This demonstrates that the proposed joint InSAR-GNSS workfow can be extended to study the subtle interseismic deformations of major fault systems in Tibet and worldwide.

PS-InSAR与PSP-InSAR监测地面沉降的比较

针对覆盖杭州地区的36景COSMO-SkyMed影像,采用永久散射体合成孔径雷达干涉测量(permanent scatterer interferometric synthetic aperture radar,PS-InSAR)技术和永久散射体对合成孔径雷达干涉测量(permanent scatterer pair InSAR,PSP-InSAR)技术进行数据处理,获取研究区域的两组地面沉降信息,并对两组结果进行交叉验证。结果表明,两种技术获取的结果无论是在沉降空间分布还是在沉降量级上,都保持高度的一致性,证明两种技术获得的结果都是可靠的。

FMCW-InISAR imaging for high-speed target based on bistatic configuration

Interferometric inverse synthetic aperture radar(InISAR)imaging has been proved to be a powerful means for obtaining threedimensional(3-D)space shape of noncooperative targets.Frequency modulated continuous wave(FMCW)InISAR(FMCWInISAR)has unique advantages of low power,low cost,and small volume compared with traditional coherent pulsed InISAR.However,FMCW-InISAR imaging has two additional issues to consider,the one is the invalidation of the assumption of stop&go,which is caused by the relatively long sweep interval of FMCW;the other is the isolation of the transmitting and receiving antennas,which is the inherent issue of the transmitter-receiver community radar systems.To solve these two problems,a bistatic FMCW-InISAR imaging algorithm for high-speed targets is proposed in this paper.For improving the isolation of the transmitting and receiving antennas,a bistatic configuration based FMCW-InISAR system is designed.According to the characteristics of bistatic,a bistatic equivalent motion model and corresponding signal model are established.Since the assumption of stop&go is invalid in the case of FMCW,indicating that the target cannot be viewed as motionless during a sweep repetition interval(SRI),a parametric estimation based quadratic phase factor(QPF)compensation method is investigated to eliminate the range walk caused by the radial motion of the target during the SRI.In addition,considering the farfield trait of the target and combining the traditional InISAR imaging process,a combined QPF compensation technique is proposed to reduce the computational burden of the algorithm.Finally,the effectiveness and the robustness of the proposed algorithm are evaluated by some simulations.