Adjustment of Gravity Observations towards a Microgal Precision

Gravity observations adjustment is studied having in view to take full advantage of the modern technology of gravity measurement. We present here results of a test performed with the mathematical model proposed by our group, on the adjustment of gravity observations carried out on network design. Additionally, considering the recent improvement on instrumental technology in gravimetry, that model was modified to take into account possible nonlinear local datum scale factors, in a 1900 mGal range network, and to check its significance for microgal precision measurements. The data set of the Brazilian Fundamental Gravity Network was used as case study. With about 1900 mGal gravity range and 11 control stations the Brazilian Fundamental Gravity Network (BFGN) was used as case study. It was established mainly with the use of LaCoste & Romberg, model G, gravimeters and new additional observations with Scintrex CG-5 gravimeters. The observables involved in the model are instrumental reading, calibration functions of the gravimeters used and the absolute gravity values at the control stations. Gravity values at the gravity stations and local datum scale factors for each gravimeter were determined by least square method. The results indicate good adaptation of the tested model to network adjustments. The gravity value in the IFE-172 control station, located in Santa Maria, had the largest estimated correction of ?10.4 μGal (1 μGal = 10 nm/s2), and the largest residual for an observed reading was estimated in 0.043 reading unit. The largest correction to the calibration functions was estimated in 6.9 × 10-6mGal/reading unit.

An adjustment method for active reflector of large high-frequency antennas considering gain and boresight

The design of the Qitai 110 m Radio Telescope（QTT） with large aperture and very high working frequency（115 GHz） was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision and high pointing precision. In this paper, the properties of active surface adjustment in a deformed parabolic reflector antenna are analyzed. To assure the performance of large reflector antennas such as gain and boresight, which can be obtained by utilizing an electromechanical coupling model, and satisfy them simultaneously, research on active surface adjustment applied to a new parabolic reflector as target surface has been done. Based on the initial position of actuators and the relationship between adjustment points and target points, a novel mathematical model and a program thatdirectly calculates the movements of actuators have been developed for guiding the active surface adjustment of large reflector antennas. This adjustment method is applied to an 8 m reflector antenna,in which we only consider gravity deformation. The results show that this method is more efficient in adjusting the surface and improving the working performance.

GOCE kinematic orbit adjustment for EGM validation and accelerometer calibration

The main principle and mathematical model of GOCE kinematic orbit adjustment for Earth gravity field model （EGM） validation and accelerometer calibration are presented. Based on 60 days GOCE kinematic orbits with 1-2 cm accuracy and accelerometer data from 2009-11-02 to 2009-12-31, the RMS-of-fit （ROF） of them using EGM2008, EIGEN-SC, ITG- GRACE2010S and GOCO01S up to 120, 150 and 180 degree and order （d/o） are evaluated and compared. The scale factors and biases of GOCE accelerometer data are calibrated and the energy balance method （EBM） is performed to test the accuracy of accelerometer calibration. The results show that GOCE orbits are also sensitive to EGM from 120 to 150 d/o. The ROFs of EGMs with 150 and 180 d/o are obviously better than those of EGMs with 120 d/o. The ROFs of GOCO01S and ITG-GRACE2010S are almost the same up to 120 and 150 d/o, which are about 3.3 cm and 1.8 cm, respectively. They are far better than those of EGM2008 and EIGEN-SC with the same d/o. The ROF of GOCO01S with 180 d/o is about 1.6 em, which is the best one among those EGMs. The accelerometer calibration accuracies （ACAs） of ITG-GRACE2010S and GOCO01S are obviously higher that those of EGM2008 and EIGEN-SC. The ACA of GOCO01S with 180 d/o is far higher than that of EGMs with 120 d/o, and a little higher than that of ITG-GRACE2010S with 150 d/o. I t is suggested that the newest released EGM such as GOCO01S or GOCO02S till at least 150 d/o should be chosen in GOCE precise orbit determination （POD） and accelerometer calibration.

Characteristics of gravity anomalies and tectonic analysis of Enderby Land in East Antarctica and its adjacent areas

Enderby Land in East Antarctica and its adjacent areas,which are closely related to the Indian Plate in their geological evolution,have become one of the key zones for studies on how the Antarctic continent evolves.Based on the isostasy and flexure theories of the lithosphere and using the CRUST1.0 model as the depth constraint,this paper uses the gravity field model EIGEN-6C4 and topographic data to calculate the isostatic gravity anomalies of Enderby Land and its adjacent areas.Then,the crustal thickness of the study area is calculated,and three comprehensive geophysical interpretation profiles that vertically span the study area are plotted.The results show that the flexural isostatic gravity anomalies in Enderby Land and its adjacent areas are closely related to the regional tectonic setting,and the anomalies in different regions differ substantially,ranging from−50×10^(−5)m/s^(2)to 85×10^(−5)m/s^(2).A zone of high isostatic gravity anomalies(30×10^(−5)−80×10^(−5)m/s^(2))is distributed outside the Cooperation Sea and Queen Maud Land,which may be plate remnants generated by early rifting.Except for the Kerguelen Plateau,which was formed by a hotspot and has a crustal thickness of 15 km,the thickness of the oceanic crust in other parts of the study area changes slightly by approximately 4–9 km,with the thinnest part being in Enderby Basin.The thickness of the inland crust along the coastline increases with the elevation,with the maximum thickness reaching 34 km.The isostatic gravity anomalies corresponding to the zone of high magnetic anomalies along the continental margin of Queen Maud Land are negative and small,with an isostatic adjustment trend indicating Moho surface uplift,and those on the edge of central Enderby Land are near zero,approaching the isostatic state,which may be caused by the magmatism at the early stage of rifting.The continental-oceanic boundary should be close to the contour line of the crustal thickness 10–12 km on the outer edge of the coastline.

自适应调节重心林间运输车设计与仿真

为提高运输车在林间的工作效率,研究设计一款能够远程遥控且能根据自身运动姿态自动调节重心的小型林间履带式运输车。通过理论计算完成整车各部分机构的设计,分析整车在可调节重心机构调控下的通过性,确定可调节重心机构的控制策略,并利用Recurdyn软件对整机进行通过性模拟仿真。仿真结果表明,经过调控重心后,整机的通过性得到有效提升,整机上坡的极限角度提高17.9%,横坡的极限角度提高18.3%,极限越障高度提高18.7%,跨壕极限宽度提高13.9%。

用于快速响应负荷需求的两段式斜坡重力储能系统放电功率调节方法

斜坡式重力储能系统(GESS)放电时通常将上堆场重物块运送至下堆场。然而,当放电过程中系统负荷需求出现波动时,现有方案难以通过及时调整重物块数量来调节输出功率,导致重力储能系统响应不及时并造成额外能量损耗。通过在斜坡两侧增加辅助堆场并将斜坡分为两段,通过控制顶部堆场重物块释放数量、斜坡堆场释放高度以及斜坡堆场重物块抓取位置,实现了重力储能系统输出功率的精确控制与负荷需求的快速响应。基于Matlab/Simulink平台搭建了两段式斜坡重力储能系统仿真模型,验证了所提方法的正确性与有效性。研究成果为斜坡式重力储能系统放电功率的快速调节与精确控制提供了重要参考。

二等水准加密重力测量与数据处理

在青海省二等水准测量工作中,由于水准路线平均海拔高、高差大,大范围开展了加密重力测量工作。文章分析了二等水准路线上开展加密重力测量工作时的布点、观测以及数据处理方法,并尝试编写了加密重力测量数据处理程序,以期研究成果对其他地区开展加密重力测量工作提供借鉴参考。

地铁车辆段上盖的全框支剪力墙结构设计探讨

根据地铁车辆段上盖全框支剪力墙结构设计实践,提出该结构按现行规范设计存在的问题,包括重力二阶效应验算,周期折减系数影响,框支柱剪力调整和厚板设计验算等问题。针对上述问题,建议重力二阶效应验算采用屈曲因子不小于20作为不考虑条件;少砌体墙的(框支)框架层考虑周期折减系数的影响,对(框支)框架层楼层剪力作折减;对于特一级或一级的框支柱的弯矩或剪力调整系数下调,避免调整后剪力远大于中震剪力的不合理情况;盖上剪力墙对厚板的冲切验算用作图法验算。

A new and high-precision gravity base network in the south of the Tibetan Plateau

A new gravity base network in the south of the Tibetan Plateau was established with a FG5X absolute gravimeter and three CG-6 gravimeters.The gravity base network consists of 10 absolute gravity points and 17 relative gravity points.Processing of the absolute data,pre-processing of the relative data and gravity network adjustment model are briefly described.Based a constrained weighted least squares,the combined adjustment of absolute and relative gravity measurements results in the gravity values with a precision of about±4.1μGal.

Water storage changes in North America retrieved from GRACE gravity and GPS data

As global warming continues,the monitoring of changes in terrestrial water storage becomes increasingly important since it plays a critical role in understanding global change and water resource management.In North America as elsewhere in the world,changes in water resources strongly impact agriculture and animal husbandry.From a combination of Gravity Recovery and Climate Experiment（GRACE） gravity and Global Positioning System（GPS） data,it is recently found that water storage from August,2002 to March,2011 recovered after the extreme Canadian Prairies drought between 1999 and 2005.In this paper,we use GRACE monthly gravity data of Release 5 to track the water storage change from August,2002 to June,2014.In Canadian Prairies and the Great Lakes areas,the total water storage is found to have increased during the last decade by a rate of 73.8 ± 14.5 Gt/a,which is larger than that found in the previous study due to the longer time span of GRACE observations used and the reduction of the leakage error.We also find a long term decrease of water storage at a rate of-12.0 ± 4.2 Gt/a in Ungava Peninsula,possibly due to permafrost degradation and less snow accumulation during the winter in the region.In addition,the effect of total mass gain in the surveyed area,on present-day sea level,amounts to-0.18 mm/a,and thus should be taken into account in studies of global sea level change.

Joint solution of leveling and gravity data in crustal deformation monitoring

Repeated leveling surveys can provide important geometric information of elevation change of points, due to the effect of the earth gravity field, the observed data of leveling also contains the information of gravity field. Repeated absolute gravity surveys or relative gravity surveys can provide rich information of gravity field, but since the gravity values at the points will change along with the variation of elevation, it also contains the information of elevation variation of points. In the classical adjustment method, the two kinds of observations will be solved respectively and the complementary information will be corrected as interference or processed as noises, as a result, not only the useful information will be lost, but also the accuracy of results will be effected. In the paper, the joint solution model for both observed data has been established in an integral geodetic frame, the calculation methods have been given, the fitting and forecasting of deformation field have been studied, the verification has been made by examples and certain of useful results have been obtained. The research indicates that the joint solution can give simultaneously the elevation of surface points and its rate of change, the parameters of local gravity field and its rate of change, which is advantageous to information extraction; The accuracy of joint solution is better than that of individual solution; The rank deficient robust solution and quasi stable robust solution are better than the corresponding non robust solution; The automatic selection of quasi stable points by using the method of quasi stable robust solution can effectively resist the interference of outliers and deformation anomaly to the initial datum; for the data with many resurveys, if the dynamic quasi stable robust estimation is made, not only the reliable quasi stable points can be found dynamically, but also the dynamic variation parameters will not or be less affected by the interference of observational outliers of each period, so the posterior accuracy of dynamic parameters can be improved obviously; when the points are abundant, establishing a deformation model to interpolate the deformation at the non surveyed points and estimating the crustal deformation of a certain time are also feasible.

Analysis of datum-instability effect on calculated results of data from Longmen Mountain regional gravity network

A statistical correlation method is used to study the effect of instability of the calculation datum （ used in traditional method of indirect adjustment） on calculated gravity results, using data recorded by Longmen Mountain regional gravity network during 1996 -2007. The result shows that when this effect is corrected, anomalous gravity changes before the 2008 Wenchuan Ms8. 0 earthquake become obvious and characteristically distinctive. Thus the datum-stability problem must be considered when processing and analyzing data recorded by a regional gravity network.

云南流动重力观测中相对重力仪漂移估计方法

针对在陆地百千米以上的时变流动重力观测网络中,相对重力仪非线性漂移率和仪器性能偏差是影响观测结果精度的主要误差来源这一问题,以1990—2022年云南流动重力观测数据为例,对比传统最小二乘平差方法和贝叶斯平差方法得到的非线性漂移率结果,系统测评了贝叶斯估计方法对于提高重力平差结果精度的有效性。结果表明,可以通过贝叶斯优化方法给出合适的仪器权重和非线性漂移率,减少多台相对重力仪性能差异造成的误差和传统线性漂移计算方法造成的有效漂移遗失,提高平差结果的精度。

航空重力测量重复测线数据处理技术研究

航空动态重力测量是快速获取地球重力场信息的有效手段,从广泛噪声中高精度提取重力信息的数据处理技术是重力测量的关键环节。本文首先分析了测量噪声的来源及误差特性,且明确了现阶段常用的有限冲激响应(FIR)低通滤波器可以有效滤除高频噪声。其次,针对动态特性误差和偶然误差,提出基于经验模态分解(EMD)的误差分离方法。再次,提出了适用于多条重复测线的系统平差方法,有效抑制了低频系统误差的影响。最后,对航空实测数据进行了处理。试验结果表明,基于EMD的误差分离方法将内符合精度从2.86mGal提升至0.75mGal,重复测线系统平差方法将精度进一步提升至0.28mGal。该研究对提升航空重力测量系统在数据处理技术成熟度及实用化水平方面有重要意义。

多代卫星测高数据联合平差及重力场反演

为了解决多代卫星测高数据之间的不协调问题,基于误差验后补偿理论,提出了将传统的交叉点平差整体解法简化为两步处理法,即首先使用条件平差法对交叉点观测方程进行平差计算,然后沿测高轨迹进行海面高滤波和推估。使用新方法可大大简化联合平差的计算过程,且有利于提高计算结果的稳定性和可靠性,对规则和不规则的区域网和全球网交叉点平差问题都同样适用。实际算例证明了新方法的有效性。

利用多代卫星测高数据反演海洋重力场

为了解决多代卫星测高数据之间的不协调性问题,本文基于误差验后补偿理论,提出将传统的交叉点平差整体解法简化为两步处理法,即首先使用条件平差法对交叉点观测方程进行平差计算,然后沿测高轨迹进行海面高滤波和推估。在此基础上,本文利用多代卫星测高数据联合平差获得的结果,进一步反演了中国海及其邻域地区的重力异常,并将计算结果同海面船测数据作了比对,实际算例已经证明了新方法的有效性。

基于绝对重力基准控制的流动重力观测资料动态平差方法研究

选取滇西重力测网1986~2009年流动重力观测资料及下关、丽江、昆明3个绝对重力基准点多年复测资料作基准控制,采用线性速率模型拟合观测过程中重力场的时变信息,建立绝对重力基准点约束下的动态平差模型,讨论段差观测值及绝对重力基准观测值协方差矩阵的构建、平差模型初值选取及迭代计算等细节问题。经分析,测区内测点的重力年变率范围为（-0.039 5~0.024 1）×10-5 ms-2/a,精度范围为（0.001~0.029 8）×10-5 ms-2/a,与分期静态平差拟合结果的差异约为（0.003~0.020）×10-5 ms-2/a。在处理全国网和较大面积的区域网多年重复观测的重力资料时,尤其是多网多期重力资料联合处理时,应采用动态平差模型来获得统一时间基准和空间基准的重力变化。

多网重力数据联合平差和系统误差改正

华北地区现行的地震重力监测网由于独立联测,自成体系,绝对控制点较少,获得的重力场动态变化图像在绝对控制较弱的地区会产生畸变,也不能有效的消除仪器标定系统所引起的测量误差。本文以华北大网作为控制网,结合绝对重力点进行联合平差计算,使各省区地震重力监测网平差精度提高了(0～4)×10-8 m/s2,平差起算基准相统一,绝对控制较弱的地区畸变减小。采用相关系数检验法,对华北地区各省区地震重力监测网2010年二期重力平差计算结果进行检验,部分重力点位系统误差高达60×10-8 m/s2,经过系统误差改正后,重力场动态变化趋于一致。经过各项改正后,华北地区2010年重力场动态差分图像对地震前兆具有更好的反映。

绝对重力控制下的山西地震带2009—2012重力场动态变化

通过对山西地震带区域重力测网2009—2012年的绝对与相对重力资料的联合平差,获得了以太原绝对重力点为基准的区域重力场动态变化图像,并分析了太原绝对重力点起算值的选取问题。

南极布兰斯菲尔德海峡船测重力资料平差处理

基于中国南极考察第28航次和第30航次所获得的实测重力数据,结合NGDC的部分资料,我们采用最小二乘算法平差处理布兰斯菲尔德海峡内470 610个有效船测重力观测值点,使航次内、航次间观测误差达到极小。针对不同航次、不同船只数据交点的分布情况,对平差方式进行不同程度的微调,完成对研究区4组数据的平差。其中,中国南极考察第28航次船测数据交点误差的标准差由平差前的5.5×10-5 m/s2降为平差后的1.78×10-5m/s2,而全部125个交点平差后标准差降为1.545×10-5 m/s2。在此基础上,绘制了研究区空间重力异常图,相比卫星重力异常数据,融合成果数据能更真实地反映海底火山等特征,从而进一步提高了数据精度。