基于PS-InSAR的广西北部湾沿岸形变探测及成因分析

受强降雨等极端天气影响,广西地区沉降地质灾害频发。为保障区域可持续发展,利用36景Sentient-1A卫星影像,探究广西北部湾沿岸地区土地形变情况并分析其成因。首先基于PS-InSAR技术和SBAS-InSAR技术,获取2018年1月～2020年12月广西北部湾地区地表沉降信息。结果表明：两种方法具有高度一致性,研究区域最大累计沉降量达-78.1 mm,最大平均形变速率为-22.664 mm/a。其次结合降雨量数据与人类活动强度,分析地表形变成因,结果进一步表明：广西北部湾地区累计沉降量与人类活动强度呈现正相关;每年7、8月雨季时,地表形变速率提高,雨季结束后,部分地面出现抬升。人类活动与降雨是导致广西北部湾地区大面积不规则沉降的重要原因。     

苏州无锡常州城市群地表沉降监测

InSAR技术作为一种遥感技术,具有大范围、高精度监测的优点,可以应用于大范围的城市群地表沉降灾害监测。但目前对于苏州无锡常州城市群的监测研究相对较少。以苏州、无锡、常州城市群为例,使用两个轨道共104景哨兵数据,以一种改进的PS-InSAR技术获取了2019年这3个地区的地表沉降结果。结果表明:苏州和常州的沉降面积和量级都较大,最大累积沉降量均超过60mm,无锡地表沉降相对较小;沉降主要发生在沿湖沿江的农业种植区域,产生的原因可能与农业灌溉有关。最后将获取的时序InSAR结果与该地区的水准数据进行比较分析,两种数据具有良好的一致性,以水准数据为参考,InSAR数据的监测精度达到3.0mm/年,表明了InSAR形变监测的高精度和可靠性。     

基于时序InSAR的珠江口大面积地面沉降监测

珠江口是我国沿海地面沉降灾害较严重地区之一,长期地面沉降威胁着人类生产生活的质量和安全。针对传统InSAR在河口等沿海地区空间采样率不足的现状,采用基于KS检验和特征分解的DS-InSAR时序分析方法,获得了珠江口地区2015—2018年间地面沉降监测数据,并分析了几处沉降严重地区的沉降特征和原因。采用的DS-InSAR方法在沥青路面、裸土等非城市区域提取了较大密度的高相干点,提高了时序InSAR形变反演的精度。研究表明,研究区域总体呈地面沉降趋势且分布不均匀,珠江三角洲西北部和东南部为主要沉降区,最大沉降速率可达25 mm/a,珠江口西岸沉降相对东岸分布更广,沉降量更大。     

基于Hough变换的DInSAR环状地表形变区自动提取

针对当前DInSAR地表形变区检测依赖于人工的现状,提出基于Hough变换的环状地表形变区自动提取方法。该方法在外部DEM的辅助下,由干涉数据获取去地形效应的差分干涉图,在对差分干涉图进行边缘提取的基础上,利用Hough变换实现环状地表形变区的自动提取。采用青海门源震区Sentinel-1A数据和山东济宁矿区ALOS PALSAR数据分别进行环状地表形变区自动提取实验,验证了本文方法的有效性。     

应用INSAR进行黄河三角洲地面沉降监测研究

在分析黄河三角洲的地面沉降状况及其对国民经济造成的影响的基础上,说明了对黄河三角洲进行地面沉降研究的必要性。综述了合成孔径雷达干涉测量的基本原理,针对近年来国内外干涉合成孔径雷达(INSAR)技术在地面沉降方面的研究和应用成果,分析了合成孔径雷达干涉测量技术应用于黄河三角洲地面沉降研究的可行性。     

星站差分在海洋倾倒区水位测量中的应用

针对目前传统抛投验潮仪及常规GNSS方法在海洋倾倒区水位测量中存在的问题,提出了基于星站差分技术的海洋倾倒区水位测量的思路,对OmniSTAR系统进行收敛时间及高程精度测试,并在营口、锦州倾倒区进行应用试验。结果表明,OmniSTAR系统经过25 min收敛,高程定位精度能够达到厘米级;OmniSTAR水位测量结果与验潮仪水位保持了较好的一致性,锚定状态下的水位测量结果优于在航水位,在2级海况下,精度能够达到一般精度指标要求,验证了星站差分系统在海洋倾倒区水位测量的可行性,达到3级海况时,在航水位存在误差较大情况。     

新型绝对重力仪在海洋重力基点测量中的应用

利用自主研发的激光干涉绝对重力仪对广州海洋地质调查局海洋地质码头的三个重力基点进行绝对重力测量。通过对测量结果的分析处理和筛选,确定了各个基点的绝对重力值。测量结果表明,该方法具有快捷、高效和测量精度高的显著优势,是一次非常有意义的技术方法探索。可认为通过进一步的技术性能完善和方法改进,绝对重力测量技术将成为海洋重力测量中一种常规的基点测量手段。     

干涉雷达高度计定标检验进展

卫星雷达高度计正从传统星下点的剖面测量向宽刈幅干涉测量发展,利用卫星观测二维的高分辨率、高精度海面高度正在成为可能,国外研究人员提出SWOT(Surface Water and Ocean Topography)干涉雷达高度计计划和我国新一代海洋科学卫星任务等计划有望实现海洋亚中尺度现象的观测。定标检验是评价卫星观测资料精度和质量的必要工作,传统高度计的定标检验均为基于验潮站、GNSS(Global Navigation Satellite System)浮标、有源定标器等方式的单点比对,难以满足干涉高度计的需求。目前国内外研究人员在干涉雷达高度计的定标检验中采用了全新的技术方案,并已利用机载试验和理论模拟开展了验证工作。对近10 a干涉雷达高度计定标检验的新技术方法进行介绍和总结,希望对我国的干涉雷达高度计卫星定标计划起到借鉴作用。     

修正GPS测量舰船航向误差的环境建模法

分析了GPS测量航向时的误差来源,结合试验情况建立修正模型进行GPS航向改正,并运用到实际试验中进行模型检验,结果证明该修正方法切实可靠,能够在一定程度上提高试验精度和可靠性。     

海洋白浪与海面摩擦速度的直接同步测量及其结果分析

本文报告首次进行的海洋白浪、泡沫和沫流带与海面摩擦速度的直接同步测量结果.由此结果得海洋白浪覆盖率W_c与海面摩擦速度U_*的经验关系为W_c=1.34×10-5U_*1.93.这一关系式支持白浪覆盖率正比于海面风应力的论断;显著不同于白浪覆盖率正比于摩擦速度3次方的物理分析结果.基于此经验关系式,还对白浪在海-气交换中的作用进行了讨论.     

杭州湾沿海地区地面沉降时序InSAR监测与分析

Time-series InSAR analysis(e.g., permanent scatterers(PSInSAR)) has been proven as an effective technology in monitoring ground deformation over urban areas. However, it is a big challenge to apply this technology in coastal regions due to the lack of man-made targets. An distributed scatterers interferometric synthetic aperture radar(DSInSAR) is developed to solve the problem of insufficient samples and low reliability in monitoring coastal lowland subsidence, by applying a spatially adaptive filter and an eigendecomposition algorithm to estimating the optimal phase of statistically homogeneous distributed scatterers(DSs). Twenty-four scenes of COSMO-Sky Med images acquired between 2013 and 2015 are used to retrieve the land subsidence over the Shangyu District on south coast of the Hangzhou Bay, Zhejiang Province, China. The spatial pattern of the land subsidence obtained by the PS-InSAR and the DSInSAR coincides with each other, but the density of the DSs is three point five times higher than the permanent scatterers(PSs). Validated by precise levelling data over the same period, the DSInSAR method achieves an accuracy of ±5.0 mm/a which is superior to the PS-InSAR with±5.5 mm/a. The land subsidence in the Shangyu District is mainly distributed in the urban areas, industrial towns and land reclamation zones, with a maximum subsidence rate –30.2 mm/a. The analysis of geological data, field investigation and historical reclamation data indicates that human activities and natural compaction of reclamation material are major causes of the detected land subsidence. The results demonstrate that the DSInSAR method has a great potential in monitoring the coastal lowland subsidence and can be used to further investigate subsidence-related environmental issues in coastal regions.     

Evaluating the Performance of Using PPK-GPS Technique in Producing Topographic Contour Map

The Global Positioning System (GPS) is considered as one of the most powerful tools that are used in geodetic works. It is increasingly considered as an alternative tool for conventional surveying techniques. The goal of this research paper is to produce a methodology for generating topographic contour maps using the post-processed kinematic differential GPS technique (PPK-GPS). The performance of this technique is assessed by comparing it with the traditional spirit-leveling technique taking into consideration the accuracy, time, and cost. The study area is located along the Mediterranean coast in the Rosetta area of the middle Delta in Egypt with a total area of about 39 km². The field work includes 14 control points and about 50,000 PPK observations. In addition, 20 check cross sections that extend along the coastal line from Rosetta to El Burullus cities were observed using both spirit-leveling and GPS-PPK techniques. The results of the comparison indicate that the PPK-GPS technique can be used instead of spirit leveling in producing a topographic contour map with an accuracy of about 20 cm in orthometric height. We find that the PPK-GPS technique reduces the estimated time of leveling works in our study area by about 70%.     

基于时序InSAR的九龙江河口地区地面沉降时空演变规律及成因分析

为探明九龙江河口地区地面沉降情况,本研究采用小基线集合成孔径雷达干涉测量（small baseline subset interferometric synthetic aperture radar, SBAS InSAR）和永久散射体合成孔径雷达干涉测量（persistent scatterer interferometric synthetic aperture rader, PS InSAR）技术获取了2017年1月至2022年3月地面沉降的时空分布信息和演变规律,并结合实地调查数据和水文地质调查监测资料对地面沉降成因进行了系统分析。研究结果表明：SBAS InSAR和PS InSAR两种方法均发现在研究期间九龙河口地区地面整体呈现出沉降趋势,SBAS InSAR监测结果发现研究区沉降速率为6.2 mm/a;研究期间该区域的沉降中心持续扩大且沉降量呈增加趋势,最大累积沉降量达到250 mm以上,主要分布在浮宫镇中南部地区、海澄镇、东园镇中南部地区、角美镇和榜山镇东南部地区;该区域由于大量抽取地下水用于养殖,地下水位下降,引起淤泥层发生固结排水、压密,从而导致地面沉降。     

一种区域似大地水准面模型拟合方法分析

GPS技术结合(似)大地水准面模型,可快速高精度的获取测点正常高,因此精化区域(似)大地水准面成为各国家和地区建立现代高程基准的重要任务。利用GPS水准进行区域似大地水准面拟合,通过实验比较分析了二次多项式、三次多项式、多面函数、移动曲面模型,论证了各自模型的特点,实验结果表明:对于地势较平坦的实验区,以上几种方法拟合的区域似大地水准面精度都在4cm以内,都能满足一般工程应用的精度要求,其中移动曲面模型拟合的实验区似大地水准面最佳。     

DL101C数字水准仪在二等水准测量中的精度分析

介绍了数字水准仪的测量原理,根据工作经验提出了使用数字水准仪进行高精度水准测量应注意的若干问题,将DL101C数字水准仪应用于二等水准测量任务并对其测量精度进行了分析。结果表明,该数字水准仪具备较高的测量精度,能够很好的用于高精度水准测量。最后提出了一些实际作业中的使用建议。     

基于水准测量技术的填海人工岛沉陷监测实践

近年来随着填海人工岛的增多,其安全性备受关注。人工岛吹填区域软土地基物理力学参数差异大,地面沉陷持续时间长、成因机制复杂和防治难度大,沉陷监测工作具有重要意义。利用精密水准测量技术,通过长期跟踪监测,分析了人工岛吹填区域的变形特征,综合评估了沉降稳定性,为人工岛的环境保护、后续设计施工建设提供科学决策依据。     

Route height connection across the sea by using the vertical deflections and ellipsoidal height data

Distance between the main land and island is so long that it is very difficult to precisely connect the height datum across the sea with the traditional method like the trigonometric leveling,or it is very expensive and takes long time to implement the height transfer with the geopotential technique.We combine the data of GPS surveying,astro-geodesy and EGM2008 to precisely connect the orthometric height across the sea with the improved astronomical leveling method in the paper.The Qiongzhou Strait is selected as the test area for the height connection over the sea.We precisely determine the geodetic latitudes,longitudes,heights and deflections of the vertical for four points on both sides across the strait.Modeled deflections of the vertical along the height connecting routes over the sea are determined with EGM2008 model based on the geodetic positions and heights of the sea segmentation points from DNSC08MSS model.Differences of the measured and modeled deflections of the vertical are calculated at four points on both sides and linearly change along the route.So the deflections of the vertical along the route over the sea can be improved by the linear interpolation model.The results are also in accord with those of trigonometirc levelings.The practical case shows that we can precisely connect the orthometric height across the Qiongzhou Strait to satisfy the requirement of order 3 leveling network of China.The method is very efficient to precisely connect the height datum across the sea along the route up to 80 km.     

GPS在天津市地面沉降监测中的应用

结合天津市GPS基准站和一级GPS监测点数据,进行区域地表形变监测数据处理与分析,重点介绍了GPS变形监测技术中高精度数据处理时的参数设置及成果精度评定准则,并通过同期监测的水准数据和GPS数据进行对比分析,验证了GPS监测技术应用于地面沉降监测的可行性。     

On the Impact of Mispointing Error and Hamming Filtering on Altimeter Waveform Retracking and Skewness Retrieval

An adequate conceptual definition of the geoid is essential for the unambiguous combination of satellite tracking data, satellite al‐timetry, and surface gravity measurements to obtain sea surface topography. The factors influencing the selection of a particular level surface of the earth's gravity field include the purpose(s) for which the geoid is to be used at the 5‐cm level, and the types of data to be used in achieving these objectives. The principal reasons for high precision determinations of the shape of the geoid are: the determination of sea surface topography for applications in oceanography; and the unification of leveling datums with a resolution equivalent to that of first order geodetic leveling. A conceptual definition of the geoid acceptable to oceanographers would be: The geoid for a selected epoch of measurement is that level surface of the earth's gravity field in relation to which the average non‐tidal (or quasi‐stationary) sea surface topography is zero as sampled globally in ocean regions. In the geodetic context, it would be convenient, though not essential, to modify this definition in such a way that the global sea surface topography had zero mean as sampled for evaluations of the geodetic boundary value problem. In either case, a basis exists for unifying all leveling datums serving areas in excess of 10⁶ km², using either gravity anomaly data for the regions or precise determinations of position at first order bench marks. Unfavorable signal‐to‐noise ratios can pose problems when dealing with datums serving smaller areas. Elevation and gravity data banks must be correctly referenced to leveling datums prior to use in sea surface topography determinations. A recent attempt to upgrade the Australian gravity anomaly data bank indicates that all current data banks of this type are inadequate for the task. It is unlikely that time variations in the radial position of the geoid as conceptually defined above, will exceed ±5 cm per century, provided the rate of earth expansion was less than 1 part in 10¹⁰ yr^‐l and there is no dramatic change in the present rate of secular change in Mean Sea Level.     

联合升降轨Sentinel-1A的地表形变监测技术研究

河谷型、海岸带、海岛礁以及滩涂等区域地表形变信息的准确获取,迫切且关键。利用25景升轨和28景降轨Sentinel-1A数据,基于SBAS-InSAR技术,获取兰州城区2014年10月~2016年9月的地表沉降速率图和沿视线方向(line-of-sight,LOS)的时相位移量,探讨升降轨数据在河谷型城市地表形变监测中的适用性。结果表明:升降轨Sentinel-1A数据之间的时相位移量具有高度关联性,其中升轨数据在地形起伏较大区体现出良好的干涉性,而降轨数据在平坦区表现出较好的监测能力。兰州城区大部分区域处于稳定状态,但沙井驿、九州、小达坪、东岗、伏龙坪、西客站以及周边区域地表存在沉降趋势,最大沉降速率可达30 mm/年。联合升降轨Sentinel-1A数据监测河谷型、海岸带、海岛礁以及滩涂等区域地面沉降具有可行性和可靠性。