航空矢量重力测量中载体加速度矢量的确定

首先推导了当采用相位时序差分法时利用双差观测量确定载体加速度的数学模型，理论上分析了加速度的确定精度。然后应用CHAGS的试验数据，分析出静态测量和动态测量时加速度矢量的确定精度可以达到亚毫伽级，与理论上的分析一致。可见，完全能够满足航空矢量重力测量的精度要求。     

AUV水下移动重力测量建模及误差分析

水下移动重力测量能够连续实施近水底的重力勘测,如使用自主水下无人航行器(AUV)还能允许水面母船同时执行多个任务,进而降低水下重力测量相关的高昂成本和准入门槛。研究了水下移动重力测量的基本原理和方法,建立了水下移动重力测量模型和相应的误差模型,重点分析了捷联式重力仪的传感器、姿态、位置、速度等误差源。讨论了达到 1 mgal 测量精度的可行性以及对水下定位设备的性能要求。 经计算,在重力传感器与捷联式航空重力仪一致,水声定位系统定位精度达到测量斜距的 0.5%,水压深度计测深测量精度达到 5 cm,多普勒计程仪测速精度达到 0.1 m/s 的情况下,可以确保水下移动重力测量达到精度要求。     

矢量重力测量系统的仿真

基于矢量重力测量数学模型，仿真了一段5000S的飞行过程，模拟了其SINS／GPS数据。详细描述了捷联惯性导航系统(SINS)中加速度计和陀螺数据仿真的方法，并给出了求解扰动重力的算法。仿真结果显示卡尔曼滤波器能有效地抑制误差积累。仿真的SINS／GPS数据可用于航空矢量重力测量的算法研究。     

重力场辅助水下导航对惯导仪器的要求

水下重力测量的准确性是决定重力场辅助水下导航可行性的一个重要指标。从厄特弗斯改正公式出发，详细分析了纬度、航向、航速精度对厄特弗斯改正的影响方式和影响大小，并以当前海洋船测重力精度作为厄特弗斯改正的误差限定，分析了满足该条件下水下载体的航向、航速需要达到的精度指标，提出了利用惯性系统进行水下重力测量误差修正时对导航硬件的要求。     

海洋重力测量中厄特沃什效应的合理改正

在海洋重力测量中,厄特沃什(Eoetvoes)改正误差一直是影响测量精度的主要误差源。对测量过程的分析可以发现,原始采集的重力值实际上是经过低通滤波后一段时间内的平均重力变化,而一般的Eoetvoes改正方法计算所得的只是某一时刻的改正值,这种差异导致了重力数据精度的下降。针对这种情况,提出了合理的滤波Eoetvoes改正方法,使改正值和重力值达到了完全对应。最后以L＆R的S型海洋重力仪的测量数据为例,具体地说明了这种新方法的改正效果。     

基于SINS/DGPS的捷联式航空重力矢量测量

国防科学技术大学研制成功了我国首套具有自主知识产权的捷联式航空重力测量系统SGA-WZ01。该重力测量系统由捷联式惯性导航系统(SINS)和差分全球定位系统(DGPS)组成。2012年4~5月,在南海某海域进行了飞行试验以测试这一新型重力仪的精度。描述了该系统的构成和数据处理过程,在数据处理中应用了全球重力场模型对重力测量结果进行校正。试验结果表明,该系统不仅可用于重力标量测量,还可用于矢量测量。重复测线的数据表明了该系统测得的重力异常的重复性可达到1.5m Gal,经过全球重力场模型校正之后北向分量的重复性为7.46m Gal,东向分量的重复性为4.46m Gal。     

导航型GPS在海上地球物理勘探中的应用──卫导数据随机噪声处理

分析了导航型GPS在海上地球物理勘探应用中存在的问题，着重研究了卡尔曼滤波对号航数据中航向和航速的处理；提出两种滤波模型，对模拟的导航数据和真实航行数据进行计算，并将结果用于重力测量数据的Eotvos改正，对出现的问题进行了讨论。文章提出适当的处理方法，使导航型GPS适应海上地球物理勘探的要求，提高了导航精度和满足测量了精度。     

几种卫星测高海洋重力场模型精度比较分析

以中国南海部分海域作为试验区,依据测区船载重力测量结果分别对S&S V28.1、S&S V29.1、DTU15和DTU17卫星测高海洋重力场模型开展了精度评估与分析工作。首先利用EIGEN6C4超高阶位系数模型计算得到的参考重力异常,使用多项式拟合技术对船载重力异常进行了长波误差改正;然后借鉴3σ准则进一步控制船载重力测量结果质量;最后以RMS作为精度主要评价指标,完成了对4种海洋重力场模型精度评估。结果表明,4种海洋重力场模型检核精度整体相当,其中S&S V29.1检核精度略高于S&S V28.1,4种重力异常模型在试验海域精度大致在1.5~6mGal之间。试验结论对于后续重力场模型应用具有一定参考价值。     

海空重力测量及应用技术研究进展与展望(三):数据处理与精度评估技术

系统分析总结了海空重力测量数据预处理即各项环境效应改正技术的研究现状及发展方向,简要论述了海空重力测量数据精细处理即数据滤波与误差补偿技术的研究动态及发展前景,分析讨论了海空重力测量精度评估技术的研究进展及发展思路,为海空重力测量数据处理及精度评估技术的未来发展提供参考。     

海岛重力测量负荷改正及其影响因素分析

利用927工程海岛绝对重力测量数据,研究了海潮负荷改正计算软件、海潮模型以及地球模型三因素对绝对重力海潮负荷改正的影响。根据计算结果,观测期间由不同海潮负荷计算软件造成的海潮重力值差异可达5.985 7μGal,不同海潮模型的差异可达2.532 7μGal,不同地球模型的差异可达5.928 3μGal。结论认为,在海岛绝对重力测量数据处理中,必须充分考虑以上因素造成的海潮负荷改正差异。     

Airborne Gravity Surveys Over Taiwan Island and Strait,Kuroshio Current and South China Sea: Comparison of GPS and Gravity Accuracies at Different Flight Altitudes

We compare the accuracies of GPS and gravity observations obtained from three airborne gravity surveys over Taiwan Island at altitude 5000 m and over Kuroshio Current, Taiwan Strait, and Dongsha Atoll at altitude 1500 m. A kinematic network adjustment was used to determine the positions of the aircrafts. GPS positioning errors are at the decimeter-level, which are not entirely propagated to velocity and acceleration errors due to cancellation of long wavelength errors. Outliers are downweighted in the Gaussian filtering to improve the gravity accuracy, especially at altitude 1500 m. Compared with the upward-continued gravity, the gravity anomalies from the 1500-m surveys show a consistent accuracy of about 3 mgal; the accuracy from the 5000-m survey is degraded, especially over high mountains. The RMS crossover differences at 1500 m and 5000 m are all below 3 mgal, suggesting flight altitudes do not affect the crossover difference. Coherence analysis suggests that the spatial resolvable wavelengths of the airborne gravity range from 4 km (altitude 1500 m) to 6 km (altitude 5000 m).     

Airborne Gravimetry Survey for the Marine Area of the United Arab Emirates

The Military Survey Department (MSD) of the United Arab Emirates (UAE) undertook an airborne gravity survey project for the marine area of the country in 2009, especially to strengthen the marine and coastal geoid in the near-shore regions. For the airborne gravity survey, 5 km spacing coast-parallel flight lines were planned and surveyed. These lines were supplemented by cross-lines in order to assess the quality of the airborne gravity surveys. The flight lines were extended 10 km, spacing lines further offshore. A Beech King Air 350 aircraft was used for the surveys, collecting data at a typical flight speed of 170 knots and a typical flight elevation of 900–1500 m, depending on weather conditions and topography. Gravity was measured with a ZLS-modified LaCoste and Romberg gravimeter (S-99), augmented with a Honeywell strap-down inertial navigation system unit. The estimated accuracy for the airborne gravity data is better than 2.0 mGal r.m.s., as judged from the airborne track crossovers. The new airborne gravimetry data changed the UAE coastal geoid by up to 30 cm in some regions, highlighting the importance of airborne gravity coastal surveys.     

利用空中球面边值问题确定似大地水准面

针对航空重力向下延拓计算过程中的不稳定性,提出了扰动位空中球面边值问题,以航空重力测量数据作为扰动位在空中球面上满足的边值条件,得到扰动位空中球面边值问题,在球外部即为经典的球外边值问题,但对于球内直到地面则没有封闭的解析形式,给出了空中球面球内到地面区域的级数解,对于认识空中重力测量数据向下延拓特征和实际应用具有参考意义。利用地面实测数据计算结果表明,对于1km航高的测量数据,一阶解可满足厘米级高程异常的解算精度。     

Dynamic parameters in models of atmospheric vortex structures

Vortex simulation and the computation of fields of dynamic parameters of vortex structures (velocity, rotor velocity, and helicity) are carried out with the use of exact hydrodynamic equations in a cylindrical coordinate system. Components of centripetal and Coriolis accelerations are taken into account in the initial equations. Internal and external solutions are defined. Internal solutions ignore the disturbances of the pressure field, but they are considered in external solutions. The simulation is carried out so that the effect of accounting for spatial coordinates on the structure of the above fields is pronounced. It is shown that the initial kinetic energy of rotating motion transforms into the kinetic energy of radial and vertical velocity components in models with centripetal acceleration. In models with Coriolis acceleration, the Rossby effect is clearly pronounced. The method of an “inverse problem” is used for finding external solutions, i.e., reconstruction of the pressure field at specified velocity components. Computations have shown that tangential components mainly contribute to the velocity and helicity vortex moduli at the initial stage.     

A three-dimensional theory for the development and migration of deep sea sedimentary waves

A perturbation model is presented for a velocity field of a bottom current flowing over a sinusoidal topography or an obstacle. The model extends existing theory by taking into account the three-dimensional Coriolis vector and an initial horizontal velocity vector at any orientation. One possible mechanism of the development of sedimentary waves in the vicinity of an obstacle by an arbitrarily oriented initial horizontal current is analyzed in detail. Space-stationary fluid particle oscillations are initiated on the downstream side of an obstacle, which can result in sedimentary waves. The model shows that their wavelength depends on latitude, water depth, obstacle width and orientation as well as the initial current direction and intensity. The model defines intervals for current velocities normal to the wave crest, for which the sedimentary waves grow (or are destroyed) or migrate in a certain direction. Information derived from bathymetric and seismic surveys, such as wavelength, height, orientation and migration direction of mudwaves, can be used to calculate the velocity component across the wave crest and to estimate the current direction, as is demonstrated for an example from the Argentine Basin (Project MUDWAVES, Site 5).     

The rôle of the complete Coriolis force in cross-equatorial flow of abyssal ocean currents

Ocean currents flowing close to or across the equator are strongly constrained by the change in sign of f, the locally vertical component of the Earth’s rotation vector, across the equator. We investigate these currents using a shallow water model that includes both the locally vertical and locally horizontal components of the Earth’s rotation vector, thus accounting for the complete Coriolis force. We therefore avoid making the so-called “traditional approximation” that retains only the part of the Coriolis force associated with the locally vertical component of the rotation vector. Including the complete Coriolis force contributes an additional term to the fluid’s potential vorticity, which may partially balance the change in sign of f as fluid crosses the equator over suitably shaped bathymetry.We focus on the Antarctic Bottom Water, which crosses the equator northwards in the western Atlantic ocean where the local bathymetry forms an almost-zonal channel. We show that this bathymetry facilitates the current’s equatorial crossing via the action of the “non-traditional” component of the Coriolis force. We illustrate this process using both analytical and numerical solutions for flow of an abyssal current over idealised equatorial topography. We also consider the one-dimensional geostrophic adjustment of a body of fluid across the equator, and show that the “non-traditional” contribution to the fluid’s angular momentum permits a larger cross-equatorial transport. These results underline the importance of including the complete Coriolis force in studies of the equatorial ocean, particularly in the weakly-stratified abyssal ocean where the non-traditional component is most pronounced.     

Heterogeneous Gravity Data Fusion and Gravimetric Quasigeoid Computation in the Coastal Area of China

ABSTRACT

Different types of gravity observations are available over coastal areas. The main challenge for coastal geoid determination is the proper fusion of heterogeneous gravity data including land, shipborne, airborne, and altimetry-derived gravity data. This paper describes the gravity data fusion and the computation of the gravimetric quasigeoid in the coastal area of mainland China. An iterative procedure of the weighted least-squares prediction based on rectangular harmonic functions is used for merging the land, altimetric, shipborne, and airborne gravity data. Applying the analytical continuation method in Molodensky's theoretic frame, the merged gravity data are then used to determine the gravimetric quasigeoid model by using the generalized Stokes' integral in a remove-compute-restore fashion. The gravimetric quasigeoid model is compared with the height anomalies determined at 662 GPS leveling points over the coastal region of mainland China, where both the geodetic height and the normal height are known. The standard deviations of the differences in the coastal provinces range from 1.8 to 4.4 cm. For the entire computation area, the mean and standard deviation of the differences are 27.9 and 3.9 cm, respectively.     

海空重力测量技术体系构建与研究若干进展(一):需求论证设计与仪器性能评估技术

简要分析介绍了海洋重力场信息的应用价值、海空重力测量技术的科学含义、研究内容、体系架构和研究目标,重点分析评述了作者所在研究团队在海空重力测量技术体系建设领域取得的一些有理论意义和实用价值的研究成果,主要从各项关键技术的研究背景、研究思路、难点突破、成果应用前景等几个方面进行了分析和总结,回答了该研究领域涉及理论方法和工程应用的一系列科学问题。其目的之一是向读者成体系地推荐我们多年积累的研究成果,目的之二是想借此机会通过回顾和梳理研究团队的发展轨迹和科学感悟,在新的起点上定位未来的发展方向、发展目标和发展思路。分三个部分进行介绍,本文为第一部分,主要涉及需求论证设计和仪器性能评估两个领域的研究成果。