利用附加系统误差参数的升降轨InSAR-GPS数据融合方法建立三维形变场

针对合成孔径雷达干涉测量技术（interferometric synthetic aperture radar,InSAR）监测形变时高空间分辨率的优势以及GPS监测数据高精度、高时间分辨率的特点,对升、降轨InSAR与GPS数据融合获取高精度的三维形变场的方法展开研究。提出以高精度的GPS观测值为约束,对升、降轨InSAR观测方程分别添加一个跟点的位置有关的系统误差函数,以对InSAR数据中残留的系统误差进行修正,减弱或消除系统误差的影响。模拟数据和实测数据表明,该方法能够有效地补偿不同轨道InSAR数据与GPS数据间的系统误差影响,且计算简单;采用附加系统误差参数的升、降轨InSAR-GPS综合形变分析模型建立的三维形变场具有更高的精度。     

Deriving 3D coseismic deformation field by combining GPS and InSAR data based on the elastic dislocation model

The density of GPS measurements is usually one of the key issues in resolving 3-D coseismic deformation field from integrating GPS and Interferometric Synthetic Aperture Radar (InSAR) measurements with pure mathematic interpolation methods An approach that combines the elastic dislocation model with the Best Quadratic Unbiased Estimator (BQUE) or a robust estimation method named IGG (Institute of Geodesy and Geophysics) is proposed to reconstruct 3-D coseismic deformation field, in which only a small amount of GPS data is needed to produce a reasonable initial 3-D coseismic deformation. Then the BQUE and IGG are used to weight the InSAR and GPS measurements to avoid computational issues caused by the negative variance problem and to decrease the impact from gross errors. The Wenchuan earthquake is used to test the proposed method. We find that the developed method makes it possible to use only a few GPSs and InSAR data to recover the 3-D coseismic deformation field, which offers extensive future usage for measuring earthquake deformation, particularly in some tectonically active regions with sparse GPS measurements.     

MODIS水汽反演用于InSAR大气校正的理论研究

大气效应尤其是大气水汽的影响是InSAR干涉测量中主要的误差源和限制因素之一,因此高精度的InSAR应用迫切需要及时掌握大气水汽含量及其时空变化。本文深入分析了利用MODIS的水汽反演结果进行InSAR干涉测量大气校正的可行性,对MODIS近红外水汽反演结果与地基GPS水汽探测结果进行了比较和分析。同时根据GPS解算结果,利用实例讨论了基于地面气象参数的水汽延迟模拟的效果。     

Integrity monitoring of fixed ambiguity Precise Point Positioning (PPP) solutions

Traditional positioning methods, such as conventional Real Time Kinematic (cRTK) rely upon local reference networks to enable users to achieve high-accuracy positioning. The need for such relatively dense networks has significant cost implications. Precise Point Positioning (PPP) on the other hand is a positioning method capable of centimeter-level positioning without the need for such local networks, hence providing significant cost benefits especially in remote areas. This paper presents the state-of-the-art PPP method using both GPS and GLONASS measurements to estimate the float position solution before attempting to resolve GPS integer ambiguities. Integrity monitoring is carried out using the Imperial College Carrier-phase Receiver Autonomous Integrity Monitoring method. A new method to detect and exclude GPS base-satellite failures is developed. A base-satellite is a satellite whose measurements are differenced from other satellite’s measurements when using between-satellite-differenced measurements to estimate position. The failure detection and exclusion methods are tested using static GNSS data recorded by International GNSS Service stations both in static and dynamic processing modes. The results show that failure detection can be achieved in all cases tested and failure exclusion can be achieved for static cases. In the kinematic processing cases, failure exclusion is more difficult because the higher noise in the measurement residuals increases the difficulty to distinguish between failures associated with the base-satellite and other satellites.     

2016年意大利阿马特里切Mw 6.2地震震源机制InSAR反演

2016年8月24日，意大利中部阿马特里切（Amatrice）地区发生Mw 6.2地震。采用ALOS-2条带模式和SENTINEL-1A宽幅模式的合成孔径雷达（synthetic aperture radar，SAR）数据分别进行SAR差分干涉测量处理，获取了该地震的同震形变场。结果显示，本次地震造成意大利中部地区发生明显的地壳形变，在雷达视线向最大沉降量达19.6 cm。基于合成孔径雷达干涉测量（interferometry synthetic aperture radar，InSAR）和GPS同震形变场数据对此次地震的发震断层进行联合反演，通过改进倾角和平滑系数获取方法，得到了最优滑动分布模型。通过使用单断层模型和双断层模型进行反演可知，双断层模型反演结果优于单断层反演结果，两种模型下反演模型相关系数分别为0.85和0.89，发震断层走向分别为160°和158°，倾角分别为44°和46°，倾滑分布主要位于地下5~7 km，平均倾滑角为-80°，最大倾滑量0.9 m位于地壳深度5 km处，该发震断层是亚平宁冲断带的一部分，为NW-SE向延伸的正断层，断层长约20 km。综合使用地震同震形变场和GPS数据对震源机制进行反演、模拟和分析，获取了高精度的震源参数，可以为分析地震危险性和断层破裂参数等提供数据支持。     

Tropospheric corrections to SAR interferometry from GPS observations

Interferometric synthetic aperture radar (InSAR) techniques have been recognized as an ideal tool for many ground deformation monitoring applications. However, the spatially and temporally variable delay of the radar signal propagating through the atmosphere is a major limitation to accuracy. The dominant factor to be considered is the tropospheric heterogeneity, which can lead to misinterpretation of InSAR results. In this paper, a between-site (BS) and between-epoch (BE) double-differencing algorithm for the generation of tropospheric corrections to InSAR results based on GPS observations is tested. In order to correct the radar results on a pixel-by-pixel basis, the GPS-derived corrections have to be interpolated. Using experimental data it has been found that the inverse distance weighted and kriging interpolation methods are more suitable than the spline interpolation method. Differential corrections as large as several centimeters may have to be applied in order to ensure sub-centimeter accuracy for the InSAR result. The algorithm and procedures described in this paper could easily be implemented in a continuous GPS network data center. The interpolated image of BS, single-differenced tropospheric delays can be derived as a routine product to assist radar interferometry.     

InSAR生成DEM中WRF大气校正

利用星载重复轨道合成孔径雷达干涉测量InSAR技术获取数字高程模型(DEM),无法避免大气延迟效应的影响。InSAR大气校正的方法很多,但在DEM获取方面的大气校正研究却非常少见。本文研究星载重轨InSAR生产DEM时利用大气数值模式WRF(Weather Research and Forecasting model)得到的水汽结果进行大气校正的问题,重点讨论大气校正的策略,包括WRF模式设置和大气校正时机的选择,简要介绍了基于WRF运算结果的大气校正方法。利用Terra SAR-X数据进行实验,检验了所提出方法的有效性,证明了在干涉相位解缠前进行大气校正,比在相位解缠后进行的效果更好。将所提出方法应用于多基线、多波段InSAR干涉结果融合中,实验结果表明大气校正能够有效降低误差,对于相干性较高的地区效果更好。     

GPS -InSAR合成方法用于地面沉降监测的可行性展望

GPS技术在地面沉降领域的应用已日臻成熟并完善；InSAR技术在地面沉降领域的应用已经开始但还未成熟，目前是研究热点。GPS—InSAR合成方法是将GPS高时间分辨率和InSAR高空间分辨率进行有效的统一，使两种技术达到互补，从而发挥各自的优势。本文指出了GPS—InSAR合成方法用于地面沉降监测的可行性，并对两种实施方案进行了探讨。最后对西安地区开展GPS—InSAR研究进行了展望。     

基于CGPS数据的InSAR对流层延迟改正研究

利用CGPS数据和站间、历元间的双差模型来计算InSAR大气延迟改正量。通过新西兰GEONET站网CGPS数据,研究了多雨山区的InSAR对流层延迟内插模型及对流层延迟参数估计个数问题,实验表明IDW和Kriging内插模型都能较好的适用于多雨山区的InSAR对流层延迟改正量内插,每隔5分钟估计一个对流层参数是比较合理的。     

GPS与InSAR数据融合在矿山开采沉陷形变监测中的应用探讨

GPS与InSAR数据融合具有重要的研究意义,本文分析了传统测量方法在矿山开采沉陷形变监测中的不足,讨论了GPS与InSAR数据融合的技术优势及其在InSAR相位解缠算法、水汽模型和大气层延迟误差改正模型、时间域与空间域的融合模型和算法等方面研究内容,提出了GPS与InSAR数据融合的研究特点与具体方法,并给出了比较详细的研究方案。     

Tight integration of GPS observations and persistent scatterer InSAR for detecting vertical ground motion in Hong Kong

A method for tightly integrating GPS observations and the persistent scatterer (PS) interferometric synthetic aperture radar (InSAR) is proposed to detect vertical ground motion in Hong Kong, China. The tropospheric zenith wet delays (ZWD) derived from GPS observations at sites in the SAR scenes are used first to model and correct for the tropospheric effects in the interferograms generated from the SAR images. The vertical motion rates (VMR) of the GPS sites determined based on the continuous GPS observations obtained at the sites are then used as constraints in the PS InSAR solutions to further enhance the quality of the solutions. Data from 12 continuous tracking GPS sites in Hong Kong and 8 ENVISAT ASAR images acquired during 2006–2007 are used to demonstrate the application of the proposed method. The results from the example show that the method is capable of detecting accurately the vertical ground motion.     

GPS／GLONASS组合定位中模糊度的处理

在对GPS／GLONASS组合定位的周跳探测和修复方法进行深入研究的基础上，论述了适合于两种数据联合解算的GPS／GLONASS模糊度迭代处理方法及相应的基于FARA方法的整周模糊度固定方法。在现有BERNESE Ver4.0GSP数据处理软件的基础上，增加及改进了其中的若干模块，从而研制出组合定位系统高精度数据处理软件，并进行了试验计算。结果表明，所开发的组合定位系统数据处理软件内、外符合精度均达到mm级，证明了这种高精度相对定位理论、方法、软件的正确性和可行性。     

应用GPS观测量改正InSAR大气误差的空间插值比较

大气水汽的空间变化和时间分布是限制重复轨道干涉测量技术精度的主要因素之一。基于GPS数据,研究比较了改进后的基于地形的GPS扰动模型(GTTM)和基于地形的湍流混合模型(TDTM)。结果表明,改进的GTTM模型和TDTM模型都能有效地降低大气水汽对InSAR测量地面形变精度的影响,且TDTM插值效果更佳。     

基于边界探测的InSAR最小二乘整周相位解缠方法

为解决最小二乘相位解缠方法一直存在收敛性差和非整周性相位解算问题,提出基于解缠边界探测并搜索整周相位值的解缠方法,采用最小二乘次优解与最优解的阈值判别准则,预测解缠趋势并逐步推进相位解缠边界,并在解缠迭代计算中附加相位搜索增量以提取相位整周值。试验分别基于噪声干扰的模拟图和香港、深圳地区的ERS-1/2卫星SAR影像干涉图,采用边界探测算法进行相位解缠计算,试验结果表明,本文解缠方法对附加强噪声的模拟干涉图能正确解缠出99.5%的相位值,真实SAR影像干涉图的解缠精度达到±0.12rad。     

Radargrammetric registration of airborne multi-aspect SAR data of urban areas

In this paper, the registration of decimeter-resolution airborne multi-aspect SAR (MASAR) data of inner city areas by application of the radargrammetric range-Doppler equations is investigated. The geometrical model is adapted to linear flight trajectories and zero-Doppler processed SAR data, whereas the observed trajectory parameters are adjusted using a strict Gauss–Helmert model and known ground control points. The significance of the estimated corrections is examined and the most suitable set of free parameters is determined. Finally, the methodology is applied to real test data of an airborne campaign over the city of Munich, Germany, and the feasability of the proposed radargrammetric registration method is shown.     

升降轨InSAR与GPS数据集成反演西安形变场

根据InSAR观测量对南北向形变不敏感的特点,将内插GPS数据得到的南北向形变场信息和InSAR监测数据进行集成和融合解算,提取三维形变场。该方法有效避免了因直接忽略南北向形变而带来的精度影响问题,较好地改善了垂向形变场的反演精度。以西安市作为研究区域,融合EnviSat ASAR、ALOS PALSAR及GPS数据,反演西安市2009—2010年在东西向和垂向的绝对的年平均形变速率场(形变场),并与11个水准监测结果进行比对,发现融合反演法不仅能提供三维形变场,而且反演的垂向精度明显优于忽略南北向形变后的反演形变结果,从而对西安市地表形变有更深入的认识。     

Improving carrier-phase ambiguity resolution in global GPS network solutions

Integer carrier-phase ambiguity resolution is one of the critical issues for precise GPS applications in geodesy and geodynamics. To resolve as many integer ambiguities as possible, the ‘most-easy-to-fix’ double-difference ambiguities have to be defined. For this purpose, several strategies are implemented in existing GPS software packages, such as choosing the ambiguities according to the baseline length or the variances of the estimated real-valued ambiguities. Although their efficiencies are demonstrated in practice, it is proven in this paper that they do not reflect all effects of varying data quality, because they are based on theoretical considerations of GPS data processing. Therefore, a new approach is presented, which selects the double-difference ambiguities according to their probability of being fixed to the nearest integer. The probability is computed from estimates and variances of wide-lane and narrow-lane ambiguities. Together with an optimized ambiguity fixing procedure, the new approach is implemented in the routine data processing for the International GPS Service (IGS) at GeoForschungsZentrum (GFZ) Potsdam. Within a sub-network of about 90 IGS stations, it is demonstrated that more than 97% of the independent ambiguities are fixed correctly compared to 75% by a commonly used method, and that the additionally fixed ambiguities improve the repeatability of the station coordinates by 10–26% in regions with sparse site distribution.     

Performance analysis of integrated GPS/GLONASS carrier phase-based positioning

Due to the different signal frequencies for the GLONASS satellites, the commonly-used double-differencing procedure for carrier phase data processing can not be implemented in its straightforward form, as in the case of GPS. In this paper a novel data processing strategy, involving a three-step procedure, for integrated GPS/GLONASS positioning is proposed. The first is pseudo-range-based positioning, that uses double-differenced (DD) GPS pseudo-range and single-differenced (SD) GLONASS pseudo-range measurements to derive the initial position and receiver clock bias. The second is forming DD measurements (expressed in cycles) in order to estimate the ambiguities, by using the receiver clock bias estimated in the above step. The third is to form DD measurements (expressed in metric units) with the unknown SD integer ambiguity for the GLONASS reference satellite as the only parameter (which is constant before a cycle slip occurs for this satellite). A real-time stochastic model estimated by residual series over previous epochs is proposed for integrated GPS/GLONASS carrier phase and pseudo-range data processing. Other associated issues, such as cycle slip detection, validation criteria and adaptive procedure(s) for ambiguity resolution, is also discussed. The performance of this data processing strategy will be demonstrated through case study examples of rapid static positioning and kinematic positioning. From four experiments carried out to date, the results indicate that rapid static positioning requires 1 minute of single frequency GPS/GLONASS data for 100% positioning success rate. The single epoch positioning solution for kinematic positioning can achieve 94.6% success rate over short baselines (<6 km).     

PERFORMANCE ANALYSIS OF INTEGRATED GPS/GLONASS CARRIER PHASE-BASED POSITIONING

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