Validation and comparison of Advanced Differential Interferometry Techniques: Murcia metropolitan area case study

This paper is focused on the analysis of the performance of Stable Point Network (SPN) and Coherent Pixel Technique (CPT), which are Advanced Differential Interferometry Techniques (A-DInSAR) that estimate, among other results, mean deformation velocity maps of the ground surface and displacement time series from a SAR dataset. The test site is the metropolitan area of the city of Murcia (Spain) where a moderate slow subsidence induced by the overexploitation of aquifers is present. SAR data acquired between July 1995 and August 2005 from ERS and ENVISAT sensors have been processed by the SPN and CPT techniques and compared with in situ instrumental measurements assumed as reference. Experimental results have shown that both SPN and CPT techniques provide estimates of the deformation evolution in time with an absolute difference below 6 mm consistently in all comparisons: SPN vs extensometer, CPT vs extensometer and SPN vs CPT. The proposed validation and comparison experiment between both A-DInSAR techniques has been useful to observe their differences and complementarities.     

时序InSAR技术在地球环境监测及其资源管理中的应用:以交城-清徐地区为例

利用ALOS-1（2007-2010）、Sentinel-1A（2017-2018）存档数据对山西交城-清徐地区的地面沉降进行监测。结合小基线和永久散射体技术优点,在增加时间采样密度的基础上利用二维线性回归分析得到研究区域的形变速率和时间序列。经同期GPS观测结果校核表明:交城-清徐地区持续发生地面沉降,但山区和平原区域形变的空间分布、量级不同,引起形变原因也不同。平原地带沉降空间分布受构造断裂控制,断裂带两侧呈现明显的差异性形变,且最大沉降速率为－200 mm/a,沉降的主要原因是地下水超采,但经治理后地面沉降灾害有所缓解,表现为沉降速率小于－30 mm/a。山区主要由于矿产资源的长期开采,沉降中心不断向南移动,最大形变速率为－462 mm/a。     

Temporal and Spatial Evolution of Land Subsidence Induced by Groundwater Exploitation and Construction in the Eastern Chaoyang District,Beijing, China

Human activities have a large impact on land subsidence in great metropolitan areas. In this study, the RADARSAT-2 observation data over a 4-year period (from November 2010 to September 2014) is used to investigate the trends of land subsidence in the eastern Chaoyang District in Beijing, China, and to analyze the impact of human activities on it. The observation results indicate that the temporal and spatial evolutions trend of land subsidence in this area is uneven, with deformation rates ranging from ??116.52 to 7.1 mm/year. There are two large subsidence areas located in the northern part of the study area, and we find that the groundwater exploitation and deformation rates are strongly linearly correlated. The effect of construction on land subsidence has also been investigated. Over time, land subsidence is generally increased in the study area, with an exception at the Longfor Changying Galleria area, which is under construction during the observation period. Based on the time-series analysis of permanent scattered points in the 200 m buffer area, construction activities are observed to cause both land subsidence and upheaval deformation of the surrounding soil. During the construction period, the displacement of the surrounding soil is disturbed. After completion, the initial displacement of surrounding soil is tended to involve the uplift of the surrounding soil, followed by a gradual subsidence with time.     

Sentinel-1A TS-DInSAR京津冀地区沉降监测与分析

近年来,京津冀地区的不均匀地表沉降日趋严重,对公路、铁路等基础设施安全造成严重威胁,已引起国内外广泛关注。合成孔径雷达时序差分干涉TS-DIn SAR(Time Series Differential Interferometric Synthetic Aperture Radar)作为一种高效的广域形变测量手段,在地面沉降调查监测中已被广泛应用,但如何针对高现势性的影像数据高精准提取大范围区域地表形变是当前深化的热点。本文利用欧洲太空局发布的Sentinel-1A新型数据源,针对TOPS(Terrain Observation by Progressive Scans)模式影像间存在多普勒中心不一致问题,借助外部高精度POD(Precise Orbit Determination)轨道和DSM(Digital Surface Model)数据进行频移滤波迭代配准,并针对Sentinel-1A数据特征集成优化了基于点目标时序分析的大区域地表形变监测方法,以2015年—2016年期间的29景影像为实验数据开展了京津地区沉降监测研究,提取了北京东、廊坊及天津西等地区的沉降结果,并结合区域内典型区域人口密度、产业分布、地表覆盖和线路剖面等信息深入分析了沉降的时空分布特征和成因。结果表明,Sentinel-1A时序干涉结果在大范围地表沉降调查监测上具有可靠的应用精度。     

PALSAR和ASARPSI显著地表沉降探测与分析

永久散射体雷达干涉(PSI)已被广泛应用于城市缓慢沉降监测,但针对显著性地表沉降监测及PSI适用性的探讨较少。本文选取天津市与廊坊市城郊结合部的典型工业化城镇为研究区,分别以2007至2010年间的23幅L波段(23.6 cm)ALOS PALSAR影像和2007至2009年间的23幅C波段(5.6 cm)ENVISAT ASAR影像为数据源,使用基于相位空间相关性分析的PSI方法进行时空沉降提取,并对两个平台的结果进行对比分析和交叉验证。在此基础上,结合长短波SAR对沉降敏感性不同的特征探讨该PSI方法应用于显著沉降解算的可靠性,并结合地质条件及地下水开采信息对实验区沉降的时空分布进行深入分析和解释。研究表明,两平台的沉降结果十分吻合,在沉降漏斗区二者均方根误差(RMSE)为6.5 mm/a;实验区地表沉降呈现出显著的非均匀性,最大沉降速率超过200 mm/a,造成严重沉降的主要原因为地下水的大量开采;证实了PSI方法在显著地表沉降监测方面的有效性和可靠性。     

基于单视线向D-InSAR技术的倾斜煤层开采地表沉陷监测方法

基于合成孔径雷达差分干涉测量（differential interferometric synthetic aperture radar,D-InSAR）技术的开采沉陷监测理论和方法是矿山变形监测领域研究的热点,当前已有学者融合单视线向D-InSAR技术和开采沉陷规律成功构建了开采沉陷三维监测模型,然而由于该模型仅融合了水平煤层开采地表沉陷规律,其并不适用于倾斜煤层开采地表沉陷监测。针对上述问题,根据D-InSAR监测的视线向变形与三维变形的关系,融合倾斜煤层开采地表沉陷规律,提出了基于单视线向D-InSAR技术的倾斜煤层开采地表沉陷监测方法。模拟实验表明,所提出的方法下沉监测相对误差绝对值小于9.53%,平均为1.31%,南北方向和东西方向水平移动监测相对误差绝对值小于9.78%,平均为3.71%,满足开采沉陷监测精度要求。并利用该方法成功监测了中国山东省兖州矿区南屯煤矿9310工作面在2012-01-27—2012-02-07期间开采引起的地表移动与变形。     

利用时序InSAR技术分析北京及河北廊坊地面沉降

利用带大气估计模型的时序InSAR方法对24幅覆盖北京及河北廊坊的Envisat-ASAR影像数据进行了时序分析,获取了该地区2007年4月—2010年9月的地面沉降速率及均方差。发现了以北京朝阳区和通州区交界处为中心和以河北廊坊城区为中心的两个沉降区域,中心区平均沉降速率分别为35mm/a与22mm/a。研究区域形变速率均方差1.5mm/a。研究结果表明:利用时序InSAR技术进行城市地表沉降监测具有较好的精度及稳定性;产生该沉降的可能原因为地下水的开采、城市基础建设的发展及工业用地量、人为活动的增加。     

京津城际铁路沿线不均匀地面沉降演化特征

北京-天津（京津）城际铁路经过地面沉降漏斗边缘,其安全运营随着不均匀沉降的增加而威胁增加。采用时序干涉测量技术监测铁路沿线地表形变,结合剖面分析与时序分析方法探讨其与影响因素之间的响应特征,揭示铁路沿线不均匀地面沉降空间分布与演化特征。结果表明,梯度可以很好地体现区域地面沉降不均匀性,研究区可压缩层厚度、地下水开发利用情况、铁路运行等均与地面沉降呈现正相关关系。可压缩层的存在为沉降发生的基础条件,地下水开发利用与铁路运营为沉降产生的主导条件,二者的时空分布情况共同决定不均匀地面沉降的发展演化。     

单采煤层地面注浆充填减沉试验研究

以亳州煤业首采面注浆减沉工程为例,介绍通过地面打孔,对单煤层开采的采空离层带和冒落带进行注浆充填从而减少地表沉降的新型充填开采工艺,并对该项目应用实际效果和效益进行了分析,为实现矿山绿色开采的可能途径提供借鉴.     

双轨D-InSAR在济宁矿区地面沉降监测中的应用

合成孔径雷达差分干涉测量技术(differential interferometry synthetic aperture radar,D-InSAR)已在矿区地面沉降监测中得到了广泛的应用。结合收集到的水准数据,选取了2009-01-10至2009-02-25时间段内的两景覆盖济宁东滩矿区的ALOS PARSAR数据,并以1∶50 000的数字高程数据(digital elevation model,DEM)作为外部参考DEM,利用GAMMA软件中的双轨D-InSAR技术对矿区的地面沉降进行监测,获取了东滩矿区的差分干涉图、增强后的干涉图、相干图、沉降图等一系列结果图,并统计分析东滩矿区在该时间段的沉降量、沉降分布及沉降面积等信息;将地理编码后的沉降图与最邻近时间段的水准数据进行精度验证及分析。结果表明:双轨D-InSAR技术可以对矿区的地面沉降进行有效的监测。     

利用时序InSAR监测兰州市中心城区地面沉降

针对兰州市中心城区的地面沉降问题,该文采用PS-SBAS和PS-InSAR技术,利用2016-01-20—2019-02-21时间段内的39景Sentinel-1A/B降轨数据,使用缓冲区分析技术对兰州市中心城区轨道交通线和铁路线周边100m区域做了沉降影响分析,监测结果表明:基于Sentinel-1A/B数据和时序InSAR技术,可以准确监测城市地表的沉降和轨道交通线的沉降时空规律;沉降区域主要集中在研究区东南部的方家泉村、和平镇和猪咀岭村;软土地基下地铁的施工会导致沉降现象的发生,兰州轨道交通线和铁路线的沉降主要发生在城区东南方向;在监测时段内,使用两种时序InSAR技术监测的同名点在沉降趋势和累计沉降量上保持了良好的一致性和吻合性,但PS-InSAR的时序变化曲线较PS-SBAS更为平缓。     

利用GRACE数据进行京津冀地区地面沉降与地下水耦合分析

地下水的过量开采已导致京津冀地区出现严重的地面沉降,为了分析地下水与地面沉降之间的耦合关系,首先利用GRACE-FO数据与GLDAS数据反演出京津冀地区2016—2019年地下水变化时序;然后利用MCTSB-InSAR技术反演出该地区同时段的沉降变化时序。通过试验分别获取地下水与地面沉降的差分变化序列和变化趋势线,并引入非弹性存储系数分析地下水对地面沉降影响力的变化规律。结果表明:①当地下水迅速升高或降低时,地面沉降速率减小或增大;当地下水持续升高时,地面沉降接近停止。②沉降越严重的区域,地下水与地面沉降变化趋势的相关性越强。③由地下水变化引起沉降的能力,随沉降等级升高而变大,且该能力在不同沉降等级中随时间变化的趋势也不同。     

Advanced differential interferometry synthetic aperture radar techniques for deformation monitoring: a review on sensors and recent research development

This paper reviews the advanced differential interferometry synthetic aperture radar (A-DInSAR) techniques, with two major components in focus. First is the basic concepts, synthetic aperture radar (SAR) data sources and the different algorithms documented in the literature, primarily focusing on persistent scatterers. In the second part, the techniques are compared in order to establish more linkage in terms of the variability of their applications, strength and validation of the interpreted results. Also, current issues in sensor and algorithm development are discussed. The study identified six existing A-DInSAR algorithms used for monitoring various deformation types. Generally, reports of their performance indicate that all the techniques are capable of measuring deformation phenomena at varying spatial resolution with high level of accuracy. However, their usability in suburban and vegetated areas yields poor results, compared to urbanized areas, due to inadequate permanent features that could provide sufficient coherent point targets. Meanwhile, there is continuous development in sensors and algorithms to expand the applicability domain of the technology for a wide range of deformable surfaces and displacement patterns with higher precision. On the sensor side, most of the latest SAR sensors employ longer wavelength (X and P bands) to increase the penetrating power of the signal and two other sensors (ALOS-2 PALSA-2 and SENTINEL-1) are scheduled to be launched in 2013. Researchers are investigating the possibility of using single-pass sensors with different look angles for SAR data collection. With these, it is expected that more data will be available for various applications. Algorithms such as corner reflector interferometry SAR, along track interferometry, liqui-InSAR, and squeeSAR are emerging to increase reliable estimation of deformation from different surfaces.     

利用SBAS时序技术识别地热资源开采引起的地表形变

本文以地热资源丰富的雄安新区为研究对象,利用SBAS技术对2015年7月至2019年2月的42幅Sentinel-1区域卫星影像和2016年8月至2018年12月的10幅ALOS-2区域卫星影像进行处理,以此获取雄安新区的时间序列地表形变。研究结果表明,雄安新区整体地表沉降严重,且沉降区主要集中在雄县和容城县,其中雄县沉降最为严重,沉降中心累计沉降量超过330 mm,容城县沉降中心累计下沉量超过120 mm。结合地热井位置和地热开采历史,由时间序列分析表明,大量开采地热资源会引起地表沉降现象。     

Monitoring of urban subsidence with SAR interferometric point target analysis: A case study in Suzhou,China

Ground subsidence, mainly caused by over exploitation of groundwater and other underground resources, such as oil, gas and coal, occurs in many cities in China. The annual direct loss associated with subsidence across the country is estimated to exceed 100 million US dollar. Interferometric SAR (InSAR) is a powerful tool to map ground deformation at an unprecedented level of spatial detail. It has been widely used to investigate the deformation resulting from earthquakes, volcanoes and subsidence. Repeat-pass InSAR, however, may fail due to impacts of spatial decorrelation, temporal decorrelation and heterogeneous refractivity of atmosphere. In urban areas, a large amount of natural stable radar reflectors exists, such as buildings and engineering structures, at which radar signals can remain coherent during a long time interval. Interferometric point target analysis (IPTA) technique, also known as persistent scatterers (PS) InSAR is based on these reflectors. It overcomes the shortfalls in conventional InSAR. This paper presents a procedure for urban subsidence monitoring with IPTA. Calculation of linear deformation rate and height residual, and the non-linear deformation estimate, respectively, are discussed in detail. Especially, the former is highlighted by a novel and easily implemented 2-dimensional spatial search algorithm. Practically useful solutions that can significantly improve the robustness of IPTA, are recommended. Finally, the proposed procedure is applied to mapping the ground subsidence in Suzhou city, Jiangsu province, China. Thirty-four ERS-1/2 SAR scenes are analyzed, and the deformation information over 38,881 point targets between 1992 and 2000 are generated. The IPTA-derived deformation estimates correspond well with leveling measurements, demonstrating the potential of the proposed subsidence monitoring procedure based on IPTA technique. Two shortcomings of the IPTA-based procedure, e.g., the requirement of large number of SAR images and assumed linear plus non-linear deformation model, are discussed as the topics of further research.     

Land subsidence lagging quantification in the main exploration aquifer layers in Beijing plain,China

Land subsidence is rapidly developing across the Beijing Plain, China. Long-term intense overexploitation of groundwater is the main reason for land subsidence in Beijing. In this study, an optimized Small Baseline Subset (SBAS) interferometry method was developed to process 46 RADATSAT-2 images from 2011 to 2015 to investigate the spatial and temporal dynamics of land subsidence in the Beijing Plain. The lag time between land subsidence and groundwater exploitation was first analyzed by the Continuous Wavelet Transform (CWT) and Cross Wavelet Transform (XWT) methods Our study found that the maximum subsidence rate reached 141 mm per year. The analysis of the areas and volumes of the annual subsidence rates indicated that the overall deformation trend slowed down from 2011 to 2015. Our results indicate that the subsidence center is always located in the southeast of Chaoyang District from 2011 to 2015. The lag time between the observed subsidence and the groundwater level drops in the main exploration aquifer layers was 0.57–1.76 months. This information is helpful to reveal the mechanism of land subsidence and build hydrogeological model.     

InSAR填海区地铁沿线地表沉降反演分析

为了更好地监测和掌握深圳填海区地铁工程结束后地铁沿线的地面沉降情况,该文利用TS-InSAR技术和20景2017年8月15日—2019年3月14日的Sentinel-1A SAR数据,借助POD精密定轨星历和ASTER GDEM V2分别去除轨道误差和地形相位,反演了深圳填海区2017—2019年地表沉降时间序列,并在此基础上重点分析了填海区地铁沿线地面沉降的时空演变规律以及地面沉降成因。结果显示,填海区各地铁沿线的地面沉降特征较为明显,最大沉降速率为-17.52 mm/a。其中,宝安中心、前海湾、深圳湾区段地铁沿线的地面沉降趋势较为严重,其地面沉降呈现逐渐增强和扩散趋势。     

Subsidence in the Kathmandu Basin,before and after the 2015 Mw 7.8 Gorkha Earthquake,Nepal Revealed from Small Baseline Subset-DInSAR Analysis

Land subsidence in densely urbanized areas is a global problem that is primarily caused by excessive groundwater withdrawal. The Kathmandu Basin is one such area where subsidence due to groundwater depletion has been a major problem in recent years. Moreover, on 25 April 2015, this basin experienced large crustal movements caused by the Gorkha earthquake (Mw 7.8). Consequently, the effects of earthquake-induced deformation could affect the temporal and spatial nature of anthropogenic subsidence in the basin. However, this effect has not yet been fully studied. In this paper, we applied the SBAS-DInSAR technique to estimate the spatiotemporal displacement of land subsidence in the Kathmandu Basin before and after the Gorkha earthquake, using 16 ALOS-1 Phased Array L-band Synthetic Aperture Radar (PALSAR) images during the pre-seismic period and 26 Sentinel-1 A/B SAR images during the pre- and post-seismic periods. The results showed that the mean subsidence rate in the central part of the basin was about ?8.2 cm/year before the earthquake. The spatial extents of the subsiding areas were well-correlated with the spatial distributions of the compressible clay layers in the basin. We infer from time-series InSAR analysis that subsidence in the Kathmandu basin could be associated with fluvio-lacustrine (clay) deposits and local hydrogeological conditions. However, after the mainshock, the subsidence rate significantly increased to ?15 and ?12 cm/year during early post-seismic (108 days) and post-seismic (2015–2016) period, respectively. Based on a spatial analysis of the subsidence rate map, the entire basin uplifted during the co-seismic period has started to subside and become stable during the early-post-seismic period. This is because of the elastic rebound of co-seismic deformation. However, interestingly, the localized areas show increased subsidence rates during both the early-post- and post-seismic periods. Therefore, we believe that the large co-seismic deformation experienced in this basin might induce the local subsidence to increase in rate, caused by oscillations of the water table level in the clay layer.     

南京地铁沿线地面沉降监测与危险性评价

采用MCTSB-InSAR技术监测南京市主城区地面沉降状况,揭示研究区内地面沉降空间分布特征;通过对地铁线路进行条带空间缓冲区分析和沿线路剖面线分析,进一步研究地铁沿线的地面及周边建筑物不均匀沉降信息;针对主要影响路段进行地质灾害危险性评价,评价结果及特征点时间序列沉降结果与同时期实际情况基本吻合。研究表明,长期进行城市主城区及地铁线路地面沉降监测具有重要意义,同时地质灾害危险性评价工作能为灾害防治及评估提供可靠的支持,具有较大的应用潜力。     

Interferometric SAR Time Series Analysis for Ground Subsidence of the Abandoned Mining Area in North Peixian Using Sentinel-1A TOPS Data

The North Peixian mining area of China has rich coal resources, with total proven reserves of 2.37 billion tons. However, the underground coal mining activities have resulted in ground collapse, which has caused serious harm to the environment and threatened the lives and properties of local residents. In this study, 12 Sentinel-1A terrain observation by progressive scans (TOPS) mode acquisitions between 30 July 2015 and 13 May 2016 over the abandoned mining area in North Peixian were analyzed using the interferometric synthetic aperture radar (InSAR) time series method to detect the ground subsidence, with the maximum ground subsidence reaching 83 mm/a and an average value of about 12.7 mm/a. The subsidence results derived from the Sentinel-1A TOPS mode dataset were proven to be effective in investigating and monitoring the ground subsidence in the North Peixian mining area. Compared to the rapid deformation during the ongoing period of mining excavation, the ground subsides slowly in abandoned mining areas and shows a linear relationship with time over a relatively long period of time. Spatial correlation between the subsidence distribution and land cover was found, in that the magnitude of the subsidence in urban areas was smaller than that in rural areas, which is associated with the controlled coal mining activities under buildings, railways, and water bodies. The results demonstrate that Sentinel-1A TOPS SAR images can be used to effectively and accurately detect and monitor ground subsidence in a mining area, which is critically important when investigating land subsidence in a large-scale mining area.