华南陆地时变重力观测数据质量评估

陆面时变微重力观测常用于监测地壳内部物质变化.仪器不确定性是影响数据质量的重要因素.本文以华南地区2015年至2018年的时变重力观测数据为研究对象,分别从相对重力仪的非线性漂移特征、格值系数变化入手,引入贝叶斯分析方法,量化不确定性来源,并以网内绝对重力观测结果进行交叉检验,评估时变重力数据产品质量.研究表明:华南2015年以来的重力观测质量由于相对重力仪非线性漂移产生的不确定性较弱,格值系数不准确引起的不确定性更大,约为20×10-8 m/s2;通过绝对重力基准约束和贝叶斯优化可以明显提高数据产品精度.本文研究结果对评价陆地重力数据质量,客观地开展重力场变化解释、分析强震孕育和物质变迁等科学问题具有重要的参考价值.     

A10-022绝对重力仪在庐山短基线的测量试验与分析

A10流动式绝对重力仪通过近几年来的改进与实用研究,已说明其观测结果的稳定性、可靠性及具有较高的测量精度。利用A10-022绝对重力仪对庐山短基线部分重力基点进行绝对重力测量,试验结果表明利用A10绝对重力仪进行室外相对重力仪格值标定场的流动绝对重力测量,是可行的,测量稳定而高效,获得的各基点重力值相互独立,没有误差积累与传递,观测结果精度较高。     

海空重力测量关键技术指标体系论证与评估

技术规程是开展海空重力测量作业的重要依据。针对我国现行海空重力测量规范或标准缺乏现势性的问题,开展了海空重力测量测线布设密度、测量精度、空间分辨率、海空重力仪零点漂移与动态重复性等关键性指标分析和论证,提出了由测点重力中误差、系统差和平均误差3个指标组成的测量精度评估体系,以及由格值标定相对精度、零点月漂移量、月漂移非线性变化中误差和月漂移非线性变化限差4个指标组成的海空重力仪稳定性评估体系,给出了相关技术指标的验证和评估方法,同时对涉及船载重力测量测点归算、航空重力测量厄特沃什改正、测量平台倾斜改正及海空重力测量精度评估等关键性数学模型进行了分析和改进,旨在为下一步启动军民融合海空重力测量作业规程编制工作提供技术支撑。     

iGrav-007超导重力仪格值的精密测定

iGrav超导重力仪是当前世界上最新型的便携式相对重力仪,可提供最稳定和最高精度的连续相对重力测量。利用武汉九峰台站FG5-112绝对重力仪与iGrav-007超导重力仪连续3天的同址观测结果,基于最小二乘线性回归和迭代算法,精密确定iGrav-007的格值。数据处理结果表明,iGrav-007的格值为(-91.640 2±0.085 2)×10-8 m·s-2/V,相对标定精度为0.092 9%,连续1天的FG5绝对重力观测获得的格值精度优于0.2%,连续3天的FG5绝对重力观测获得的格值精度优于0.1%。     

不同固体潮改正公式及国家重力网的统一

本文讨论了不同的潮汐公式,及其引起的重力测量计算成果不一致的问题,计算了当潮汐改正公式不统一时,对我国范围内绝对重力测量、相对重力测量、重力仪长基线格值因子标定、重力仪短基线周期误差标定及物探重力控制测量成果的影响,分析了我国85重力基本网所选取的绝对重力控制点之间的一致性、控制点与我国85网相对联测平差结果的一致性、以及85网与我国一等重力控制同之间的一致性问题。最后,为统一我国重力控制测量成果提出了一些建议。     

灵山重力标定基线场的升级改造与复测

完成了灵山重力标定基线场的升级改造,新建4个绝对重力观测墩,改造1个相对重力标墩,对所有重力测点进行相对重力联测。测量数据分析结果显示,基线场观测墩建设和重力联测工作均符合相关要求;各相邻重力点间6台仪器测量段差互差均优于40×10~(-8) m·s~(-2);改造后的灵山重力标定基线场最大重力段差值为246 956.8×10~(-8) m·s~(-2)。对比1990年建场值和2000年复测值结果,2014年复测结果显示该基线场稳定性较好,一般重力测量的重力仪标定可以根据测程范围选择灵山重力标定基线场进行标定。     

CG-5相对重力仪野外实验精度分析

针对CG-5相对重力仪零点漂移规律对测量精度的影响及仪器系统阐述欠缺等问题,通过静态、动态和布设相对重力网实验对CG-5相对重力仪进行测试,研究CG-5型相对重力仪的漂移规律、性能及精度。结果表明,仪器的静态零点漂移线性度很好,6d的零漂率变化不大,总体呈下降的趋势。经过零点漂移改正后的动态零漂率很小,仅为5μGal/h,动态实验的动态误差为2.207μGal,在限差10μGal之内。相对重力网平差精度较高,均在限差5μGal之内。CG-5相对重力仪在测试中表现出了较稳定的状态,测得数据精度较高,符合厂商提供的标称精度。     

CG-5重力仪零漂改正及格值系数检测应用研究

利用分测线零漂改正方法和格值系数变化检测方法,对云南重力测区2014年两期CG-5重力仪观测数据进行了精细处理,获得了该地区重力场变化,并用绝对重力观测结果进行了验证。结果表明:(1)CG-5重力仪零漂率存在明显的随时间变化,C1169和C1170两台重力仪在第一期观测时间内呈近似线性的增大趋势,变化量达20×10~(-8) m·s~(-2)·h~(-1),第二期观测时间内则趋于稳定,经零漂改正后,观测数据联测精度明显提高;(2)C1170重力仪格值系数变化发生了明显变化,变化量约为-0.000 100;(3)经格值系数改正后,获得的重力变化结果与绝对重力观测结果更为一致,重力场变化图像更为清楚地反映了昭通-鲁甸断裂两侧的差异变化和鲁甸6.5级地震的发震背景,验证了大地震一般发生在与主要活动断裂一致的重力场变化正负转换带上这一结论,说明本文所用方法能有效消除观测数据中的系统误差,有利于真实重力场变化信息的获取。     

相对重力测量值的改正

影响相对重力测量精度的主要因素有潮汐、气压、仪器高、零点飘移和地下水变化以及仪器格值函数等.文中研究了在中国重力基本网2000(CGBN2000)精度要求下各影响因素的计算公式和其中存在的问题,给出了一组便于实际测量应用的计算公式;同时对重力仪格值因子的误差和选取、非构造因素中地下水活动等问题进行了讨论.     

相对重力测量值的改正

影响相对重力测量精度的主要因素有潮汐、气压、仪器高、零点飘移和地下水变化以及仪器格值函数等。文中研究了在中国重力基本网 2 0 0 0 (CGBN2 0 0 0 )精度要求下各影响因素的计算公式和其中存在的问题 ,给出了一组便于实际测量应用的计算公式 ;同时对重力仪格值因子的误差和选取、非构造因素中地下水活动等问题进行了讨论     

GT-2A航空重力仪静态测量实验及性能分析

设计静态测量实验和升降台实验对GT-2A航空重力仪的零漂率、分辨力和尺度因子进行分析。利用GT-2A定点静态连续观测数据、相对重力仪同步观测数据和固体潮模型计算的重力固体潮数据，计算了GT-2A的零漂率。固体潮改正之前和之后的计算结果表明，采用GT-2A连续静态观测数据计算的零漂率差值最大可达7.4 μGal/h；采用施测前后校准测量数据计算零漂率引入的代表误差最大为13.7 μGal/h。以上结果表明固体潮对零漂率的确定具有较大影响。测试GT-2A观测重力固体潮的能力，通过频域分析发现幅值超过30 μGal的分潮波会对GT-2A测量结果的幅-频特征产生影响，认为GT-2A的分辨力约为30 μGal。升降台实验中利用GT-2A测定重力垂直梯度，与相对重力仪测得的重力垂直梯度比较，计算出GT-2A实验量程内观测数据的尺度因子为-0.003 4 ±0.011 6。     

船载绝对重力仪测量系统的误差修正模型及不确定度分析

目前的激光干涉绝对重力仪均在静态环境下工作,而动态环境下的绝对重力测量是技术发展的热点之一。船载绝对重力测量能够很好地克服海洋相对重力测量仪器的零漂、标定、误差累积等问题,提高作业效率和可靠性。基于激光干涉绝对重力仪工作原理设计了一个船载绝对重力仪测量系统,该系统由绝对重力测量系统、陀螺仪稳定平台、力平衡式加速度计和GPS（global positioning system）组成。通过对影响船载绝对重力测量系统的垂直波动、纵摇横摇、水平波动以及厄特弗斯效应等4类干扰源进行分析,给出了该系统正常工作的动态限制条件、误差修正方法和修正精度,验证了在现有技术条件下,船载绝对重力仪测量系统的测量精度可以优于±1.1 mGal,为进一步的船载绝对重力测量实验提供理论支撑。     

Monitoring GOCE gradiometer calibration parameters using accelerometer and star sensor data: methodology and first results

The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite, launched on 17 March 2009, is designed to measure the Earth’s mean gravity field with unprecedented accuracy at spatial resolutions down to 100?km. The accurate calibration of the gravity gradiometer on-board GOCE is of utmost importance for achieving the mission goals. ESA’s baseline method for the calibration uses star sensor and accelerometer data of a dedicated calibration procedure, which is executed every 2?months. In this paper, we describe a method for monitoring the evolution of calibration parameter during that time. The method works with star sensor and accelerometer data and does not require gravity field models, which distinguishes it from other existing methods. We present time series of calibration parameters estimated from GOCE data from 1 November 2009 to 17 May 2010. The time series confirm drifts in the calibration parameters that are present in the results of other methods, including ESA’s baseline method. Although these drifts are very small, they degrade the gravity gradients, leading to the conclusion that the calibration parameters of the ESA’s baseline method need to be linearly interpolated. Further, we find a correction of ?36 × 10^?6 for one calibration parameter (in-line differential scale factor of the cross-track gradiometer arm), which improves the gravity gradient performance. The results are validated by investigating the trace of the calibrated gravity gradients and comparing calibrated gravity gradients with reference gradients computed along the GOCE orbit using the ITG-Grace-2010s gravity field model.     

A model for adjustment of differential gravity measurements with simultaneous gravimeter calibration

 A mathematical model is proposed for adjustment of differential or relative gravity measurements, involving simultaneously instrumental readings, coefficients of the calibration function, and gravity values of selected base stations. Tests were performed with LaCoste and Romberg model G gravimeter measurements for a set of base stations located along a north–south line with 1750 mGal gravity range. This line was linked to nine control stations, where absolute gravity values had been determined by the free-fall method, with an accuracy better than 10 μGal. The model shows good consistence and stability. Results show the possibility of improving the calibration functions of gravimeters, as well as a better estimation of the gravity values, due to the flexibility admitted to the values of the calibration coefficients. Received: 15 November 1999 / Accepted: 31 October 2000     

Establishment of precise gravity network of airport stations in India

A precise gravity network of thirty-five stations based on the first order gravity station at Palam airport, New Delhi (979.13433 gals—University of Wisconsin 1969 value) was established during April–June 1971, covering the entire country, in order to use them as reference bases for any future gravity surveys in India with a repeatability of ±0.05 mgal or less. The instrument, a LaCoste-Romberg geodetic gravimeter No. G-84, was transported by air over the network of airport stations embracing Trivandrum in the south, Srinagar in the north, Bombay in the west and Mohanbari in the east. The four airport stations in New Delhi, Calcutta, Madras and Bombay which were more precisely established by a large number of repeat observations were utilised as base stations for facilitating easy occupation of the remaining thirty-one stations within their respective zones. The observations were reduced by procedure which permits automatic removal of instrumental drift from the observed readings. According to the depicted drift curve, the instrumental drift though comparatively small, is found not exactly linear due to the possible tare effect observed at the initial stage and also the resulting creep drift that might have been developed during transportation of the gravimeter by air. The final results along with their probable errors of the order of ±0.01 mgal for base stations and ±0.03 mgal for other stations relative to the adopted value at Palam airport, are given in Table 1. Fourteen of the sites occupied are reoccupations of stations already established by the University of Wisconsin in 1963, and the results of the old and the new measurements as given in Table 2, are in remarkable agreement, which ensures the correctness of the calibration factors of the present instrument relative to that of the Wollard's LaCoste-Romberg gravimeter No. G-1-A actually employed in the 1963 measurements.     

国产零长弹簧原理动态重力仪首次飞行试验及精度评估

CHZ-Ⅱ重力仪是首套完全国产零长弹簧原理航空重力仪,2018年4月在陕西渭南地区进行了首次飞行试验,共完成4个架次24条测线的有效飞行,标志着我国航空重力仪在自主研发的道路上又取得了长足的进步。利用飞行地区地面重力数据对CHZ-Ⅱ重力仪的测线扰动重力和格网扰动重力数据进行精度评估,其中空中测线在10 km分辨率条件下,精度达到1 mGal。采用地形辅助法对测量形成的5'测格网重力数据进行向下延拓,经延拓至地面后精度优于5 mGal,基本满足平原地区的测量需求。