The worsening impacts of land reclamation assessed with Sentinel-1: The Rize (Turkey) test case

Massive amounts of land are being reclaimed to build airports, new cities, ports, and highways. Hundreds of kilometers are added each year, as coastlines are extended further out to the sea. In this paper, this urbanization approach is monitored by Persistent Scatterer Interferometry (PSI) technique with Sentinel-1 SAR data. The study aims to explore this technology in order to support local authorities to detect and evaluate subtle terrain displacements. For this purpose, a large 3-years Sentinel-1 stack composed by 92 images acquired between 07/01/2015 to 27/01/2018 is employed and stacking techniques are chosen to assess ground motion. The test site of this study, Rize, Turkey, has been declared at high risk of collapse and radical solutions such as the relocation of the entire city in another area are been taken into consideration. A media fact-checking approach, i.e. evaluating national and international press releases on the test site, is considered for the paper and this work presents many findings in different areas of the city. For instance, alerts are confirmed by inspecting several buildings reported by the press. Critical infrastructures are monitored as well. Portions of the harbor show high displacement rates, up to 1 cm/year, proving reported warnings. Rural villages belonging to the same municipality are also investigated and a mountainous village affected by landslide is considered in the study. Sentinel-1 is demonstrated to be a suitable system to detect and monitor small changes or buildings and infrastructures for these scenarios. These changes may be highly indicative of imminent damage which can lead to the loss of the structural integrity and subsequent failure of the structure in the long-term. In Rize, only a few known motion-critical structures are monitored daily with in-situ technologies. SAR interferometry can assist to save expensive inspection and monitoring services, especially in highly critical cases such as the one studied in this paper.     

CE-5器间分离的同波束干涉测量的准实时监测法

“嫦娥5号”探测器的组成包括轨道器、返回器、着陆器和上升器。在环月阶段,两个组合体(轨道器/返回器组合体和着陆器/上升器组合体)之间的分离实时监测,是飞行控制的关键检测段。本文提出利用甚长基线干涉测量(VLBI)测轨技术实现绕月探测器器间分离实时监测。特别是在器间分离前后,本文方法能够利用探测器器间两路下行信号进行同波束干涉测量(SBI),差分时延测量能够提高器间相对距离的解算精度。单基线试验分析表明,本文方法基于实测数据的“嫦娥3号”着陆器两天线的相对距离解算精度优于0.3m,平均相对距离误差约为0.15m,基于“嫦娥5号”仿真数据的双阈值判定对器间分离监测的响应时延优于30s。     

Investigation of the ground displacement in Saint Petersburg,Russia, using multiple-track differential synthetic aperture radar interferometry

Global sea level rise and local land subsidence might exacerbate the risk of flooding in coastal plains. Among other cities, this is also the case for the high-latitude city of St. Petersburg, which has long been threatened by flood events. To protect the urban area from storm surges, the Union of Soviet Socialist Republics (USSR) in 1978 approved the construction of the 25 km long Flood Prevention Facility Complex (FPFC), which was completed in 2011. The risk of flooding in the city area of St. Petersburg is amplified by the fact that large sections of the coastal area have been reclaimed from the sea. In this study, we investigate the temporal evolution of the ground displacement in St. Petersburg. To this end, we perform an extended analysis based on the application of a simplified version of the differential interferometric synthetic aperture radar technique, known as the minimum acceleration (MinA) approach. The MinA algorithm is a multi-satellite/multi-track interferometric combination technique that allows working with multiple sets of SAR images. The method allowed generation of time series of two-dimensional (2-D) (i.e. East-West and Up-Down) deformation of the terrain by processing two sequences of Sentinel-1A/B (S-1A/B) SAR images acquired from 2016 to 2018, along the ascending and descending flight passes. The Small BAseline Subset (SBAS) algorithm was independently applied to the two sets of SAR data to generate the relevant Line-Of-Sight (LOS)-projected ground deformation time series. Subsequently, the LOS-projected deformation products were geocoded and jointly combined. The results indicate that the deformation in the city is predominantly vertical (i.e. it is subsiding) with a maximum subsidence rate of about 20 mm/year corresponding to the newly sea-reclaimed lands. Finally, the error budget of the retrieved 2-D deformation time series has also been addressed.     

双轨D-InSAR技术监测矿区地面沉降的应用

合成孔径雷达差分干涉测量(Differential interferometry synthetic aperture radar,D-InSAR)技术在矿区地面沉降监测领域具有独特的优势和巨大的发展潜力。为分析并掌握济宁某矿区地面沉降的变化状况,选取具备高穿透植被能力的L波段的ALOS PALSAR数据,基于双轨D-InSAR技术对采煤塌陷进行动态监测,获取矿区的形变信息,并与水准数据进行对比分析,进而为有效的进行矿山地质环境保护与治理恢复提供一定的理论依据和技术支持。     

相对轨道根数的重轨InSAR卫星基线分析与控制

星载重轨干涉SAR卫星在高程测绘和形变测量中有着全天时全天候和大范围的优势,其中干涉基线是决定干涉性能的重要指标,而卫星重访轨道对干涉基线起着决定性的作用。通过对现有高分三号干涉数据轨道参数的分析,发现干涉基线相比国外先进卫星过长且稳定性有待提高。本文通过对相对轨道根数和机动控制的分析,得到满足重轨干涉SAR系统要求的稳定基线。以第一次观测的轨道为参考轨道,基于在摄动情况下重复观测轨道与参考轨道的相对轨道根数,计算得到重轨干涉基线的变化规律,并对不同纬度的观测目标进行了样例分析。在基线变化规律的基础上,利用机动速度和相对轨道根数的关系,进一步计算得到满足基线状态需求的机动控制方法。通过实际数据分析,给出了相对轨道根数变化对初始理想构型的影响,验证了重轨干涉基线变化规律符合本文的分析,并利用仿真样例给出了使得重轨干涉基线达到预期要求的机动控制方案。实际数据和仿真实验表明该模型能够通过可长时间观测并准确获得的轨道根数直接计算基线状态,并能从干涉基线需求出发,快速准确的得出对卫星的控制策略。     

Subsidence associated with the LUSI mud eruption,East Java,investigated by SAR interferometry

A mud volcano LUSI initiated its eruption on 29 May 2006, adjacent to a hydrocarbon exploration well in East Java. Ground subsidence in the vicinity of the LUSI eruptive vent was well recorded by a Synthetic Aperture Radar (SAR) PALSAR onboard the Japanese ALOS satellite. We apply an Interferometric SAR (InSAR) technique on ten PALSAR data scenes, acquired between 19 May 2006 and 21 May 2007, in order to obtain continuous maps of ground displacements around LUSI. Although the displacements in the area closest to the eruptive vent (spatial extension of about 1.5 km) are not detectable because of the erupted mud, all the processed interferograms indicate subsidence in an ellipsoidal area of approximately 4 km (north–south) × 3 km (east–west), centered at the main eruptive vent. In particular, interferograms spanning the first four months until 4 Oct. 2006 and the subsequent 46 days between 4 Oct. 2006 and 19 Nov. 2006 show at least about 70 cm and 80 cm of displacements away from the satellite, respectively. Possible causes of the subsidence, i.e., 1) loading effect of the erupted mud, 2) creation of a cylindrical mud conduit, and 3) pressure decrease and depletion of materials at depth, are investigated. The effects of the first two causes are found to be insufficient to explain the total amount of subsidence observed in the first six months. The third possibility is quantitatively examined using a boundary element approach by modeling the source of deformation as a deflating oblate spheroid. The spheroid is estimated to lie at depths of a few hundred to a thousand meters. The estimated depths are significantly shallower than determined from analyses of erupted mud samples; the difference is explained by presence of significant amount of inelastic deformation including compaction and downward transfer of material.     

优化的两步相移算法在图像加密中的应用研究

优化了此前提出的两步相移算法,仅通过两幅去除背景光强(或抑制直流分量)后的干涉图数据和一个(0, π)区间的相移值,就可以成功再现出原始物波场信息,无需借助于物光光强、参考光光强等其他辅助测量信息.与菲涅耳域的双随机相位编码技术结合,该优化算法可以应用于图像加密方案中,通过计算机仿真实验验证了所提方案的可行性,并对几何密钥的灵敏度进行了测试分析.     

InSAR技术及其在地质灾害中的应用

InSAR是在太空对地球进行3维成像技术,它标志着空间遥感从2维信息获取进入到3维信息获取的新阶段,也为大地测量带来了一场革命。该技术为地质灾害的研究提供一个全新的工具。运用InSAR和D-In-SAR技术进行地面微位移监测,是近年来发展起来并得到日益重视的新方法。本文例举了InSAR技术在地震、火山喷发和滑坡等地质灾害应用的实例。表明它在形变监测研究中有广阔的应用前景,具有不可替代的优势。     

Observations of Rotating Jets of Carbon Monoxide in Comet Hale–Bopp with the Iram Interferometer

CO was observed on March 11, 1997 in comet Hale–Bopp with theIRAM Plateau de Bure interferometer. The maps show evidence for asymmetrical patterns, due to the Existence of CO jets. Analysis of the spectra and their velocity shifts shows that there is a spiral CO jet rotating in a plane almost perpendicular to the sky plane.This is the first time that rotating jets are observed for parent molecules.We have developed a 3-D model simulating rotating spiral jets of CO gas.We present here the comparison between the observations and our model.     

激光全息干涉法研究混凝土的损伤演化规律

将实时激光全息于涉试验系统与静态承压装置相结合，在单轴连续静态荷载作用下分别对不同混凝土试块连续进行激光实时全息于涉试验动态观测，同时测量受压混凝土的应力应变关系曲线，通过数码摄像机将全息于涉条纹图传输至计算机，获取实时全息于涉条纹图。根据于涉条纹的分布规律及其路径，直观地再现了混凝土的损伤演化过程，描述了混凝土构件的损伤演化断裂特征。为混凝土结构损伤分析与诊断的深入研究探索出了有效的试验方法。