Cross-Coupling Correction for LaCoste ＆ Romberg Airborne Gravimeter

Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.     

L&R航空重力仪的水平加速度改正

L&R(LaCoste&Romberg)航空重力仪是我国首套航空重力测量系统的核心,主要由高精度的垂直加速度计和稳定平台组成。前者用于测量总加速度,后者使加速度计保持精确的垂直指向。飞行测量时,由于水平加速度的存在,稳定平台难以精确维持水平从而使加速度计偏离正确指向,由此产生了水平加速度改正。介绍了水平加速度计算的两种基本方法,即两步法与一步法,从理论上导出了其在平台倾角较小情况下的等价性。为有效地减弱因水平加速度改正不完善产生的系统性误差,提出了水平加速度改正的预滤波方法。通过平台倾角的谱分析,确定了预滤波尺度,即采用与平台稳定周期相当的低通滤波器进行预滤波。最后利用实测数据对此进行了验证和分析。结果表明,利用预滤波尺度,航空重力测量值与地面向上延拓参考值的系统差由5×10-5m.s-2减小至0.5×10-5m.s-2。     

Detection of spheriodal free oscillation excited by Peru 8.2 <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript> earthquake with five international superconducting gravimeter data

In this paper, authors obtain the spectral peaks of the earth free oscillation and check all normal modes from ₀S₀ to ₀S₄₈ accurately, with the Fourier analysis and the maximum entropy spectrum method dealing jointly with six groups of the observational residual data from five international superconducting gravimeter stations. By comparing the observational results in this paper with three former groups of observations or models, authors notice an extra discrepancy between two observational ₀S₂ modes excited separately by Peru earthquake and Alaska earthquake, which probably mirrors the anisotropy of the Earth’s inner core. The analysis on the splitting ₁S₂ mode shows that the asymmetric factor of rotationwise spectral splitting is possible to be different from that of anti-rotationwise spectral splitting.     

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LaCoste & Romberg ET型重力仪数字静电反馈系统的研制

介绍以计算机技术和采用数字比例积分微分控制器控制算法研制的数字式静电反馈系统的工作原理,并将该系统用于LaCoste & Romberg(LCR)ET20型重力仪的升级改造中.改造后LCR ET20重力仪的观测结果表明,该系统能解决模拟静电反馈系统中线性度不易调整和长期稳定度差等问题,并能提高重力仪的观测精度.     

GS型重力仪的静电反馈与静电标定

本文介绍了静电反馈及静电标定技术在GS型重力仪上的具体应用,着重阐述了它的工作原理。应用结果表明,装配有静电反馈及静电标定系统的重力仪,不但观测资料精度大大提高,而且仪器的标定既简单又准确。     

用超导重力仪观测数据精密测定地球潮汐常数

基于我国武汉超导重力仪１９８５年１１月２３日至１９９４年１２月３１日（３３２６ｄ共７９８２４ｈ整点读数值）的长周期序列重力潮汐观测数据，利用国际上通用的资料分析方法和计算机软件系统研究了重力场潮汐变化特征，精密测定了地球潮汐常数，几个主要潮波的振幅因子测定精度达０．０４％。对采用不同引潮位展开、是否考虑加权滤波、做气压改正、删除错误数据以及规定数据段均方差上限等方式对提高资料分析精度的影响问题进行了讨论。利用Ｓｃｈｗｉｄｅｒｓｋｉ全球模型对重力潮汐观测分析结果进行了海潮负荷改正，较系统地研究了观测重力残差和台站气压变化之间的相关性，在时间和频率域内测定了相应的大气重力导纳值。与Ｗａｈｒ－Ｄｅｈａｎｔ标准地球潮汐模型相比较，潮汐振幅因子的平均偏差分别是０．４％（Ｏ１波）和０．２％（Ｍ２波）。     

Least squares spectral analysis and its application to superconducting gravimeter data analysis

Detection of a periodic signal hidden in noise is the goal of Superconducting Gravimeter (SG) data analysis. Due to spikes, gaps, datum shrifts (offsets) and other disturbances, the traditional FFT method shows inherent limitations. Instead, the least squares spectral analysis (LSSA) has showed itself more suitable than Fourier analysis of gappy, unequally spaced and unequally weighted data series in a variety of applications in geodesy and geophysics. This paper reviews the principle of LSSA and gives a possible strategy for the analysis of time series obtained from the Canadian Superconducting Gravimeter Installation (CGSD), with gaps, offsets, unequal sampling decimation of the data and unequally weighted data points.     

PET型重力仪观测概况与仪器维护

通过对漳州台PET型重力仪运行4年来观测概况的介绍,总结日常观测过程中可能遇到的仪器故障或问题,并初步探讨解决仪器问题的经验办法,提高仪器维护的质量.     

基于激光干涉的新型高精度绝对重力仪

本文介绍了一种自主研发的新型高精度绝对重力仪样机,它利用激光干涉原理测量落体自由下落时相对于参考棱镜的时间位移信息,通过振动误差补偿算法提取落体下落轨迹上的时间位移坐标,然后基于最小二乘拟合法计算测点的重力加速度.在白家疃国家地球物理观象台国家重力基准点进行的对比观测试验结果与误差分析确定,样机经误差修正后的系统偏差为(-27.46～-30.59)±3.06×10-8 ms-2,2小时测量精度优于10×10-8 ms-2.