Gravity field recovery from GOCE orbits using the energy conservation approach

The sum of the dissipative energy and energy constant of the GOCE satellite is found by a priori gravity field model at first, and the GOCE dissipative energy is obtained by computing the adjacent epoch difference via the differential method. Then, a gravity field model GOCE-ECPO1, which up to the degree and order 80, is recovered by the energy conservation approach from the 103-day precise orbital data of the GOCE satellite collected from November 1, 2009 to January 12, 2010. Finally, the model is compared with existing models EGM96, ITG-CHAMP05S, EIGEN-GRACE2010S, EIGEN-6C and GO CONS GCF 2 DIR_R3. The results show that at the same order and degree, the accuracy of model GOCE-EBPO1 is higher than those of models EGM96 and ITG-CHAMP05S, but lower than those of models EIGEN-GRACE2010S, EIGEN-6C and GO_CONS_GCF 2 DIR_R3, which is mainly caused by the pole gap.

Monthly gravity field solution from GRACE range measurements using modified short arc approach

In this paper we present a series of monthly gravity field solutions from Gravity Recovery and Climate Experiment（GRACE） range measurements using modified short arc approach,in which the ambiguity of range measurements is eliminated via differentiating two adjacent range measurements.The data used for developing our monthly gravity field model are same as Tongji-GRACEOl model except that the range measurements are used to replace the range rate measurements,and our model is truncated to degree and order 60,spanning Jan.2004 to Dec.2010 also same as Tongji-GRACE01 model.Based on the comparison results of the C_（2,0）,C_（2,1）,S_（2,1）,and C_（15,15）,S_（15,15）,time series and the global mass change signals as well as the mass change time series in Amazon area of our model with those of Tongji-GRACE01 model,we can conclude that our monthly gravity field model is comparable with Tongji-GRACE01 monthly model.

Three-dimensional modelling of shear keys in concrete gravity dams using an advanced grillage method

Contraction joint shear keys are resilient features of gravity dams that can be considered to increase the sliding safety factors or minimise seismic residual sliding displacements,allowing costly remedial actions to be avoided.This paper presents a novel,robust,and computationally efficient three-dimensional(3D)modelling and simulation strategy of gravity dams,using a series of adjacent cantilever beam elements to represent individual monoliths.These monoliths are interconnected in the longitudinal direction by 3D no-tension link elements representing the lumped shear key stiffness contributions at a particular elevation.The objective is to assess the shear key internal force demands,including the axial force,shear,and moment demands.Shear key demand-capacity ratios can then be assessed with related multi-axial failure envelopes.The 3D link element stiffness coefficients were derived from a series of 3D finite element(FE)solid models with a detailed representation of geometrical features of multiple shear keys.The results from the proposed method based on advanced grillage analysis show strong agreement with reference solutions from 3D FE solid models,demonstrating high accuracy and performance of the proposed method.The application of the proposed advanced grillage method to a dam model with two monoliths clearly shows the advantage of the proposed method,in comparison to the classical approach used in practise.

WHU-Grace01s:A new temporal gravity field model recovered from GRACE KBRR data alone

A new temporal gravity field model called WHU-Grace01s solely recovered from Gravity Recovery and Climate Experiment （GRACE） K-Band Range Rate （KBRR） data based on dynamic integral approach is presented in this paper. After meticulously preprocessing of the GRACE KBRR data, the root mean square of its post residuals is about 0.2 micrometers per second, and seventy-two monthly temporal solutions truncated to degree and order 60 are computed for the period from January 2003 to December 2008. After applying the combi- nation filter in WHU-Grace01s, the global temporal signals show obvious periodical change rules in the large-scale fiver basins. In terms of the degree variance, our solution is smaller at high degrees, and shows a good consistency at the rest of degrees with the Release 05 models from Center for Space Research （CSR）, GeoForschungsZentrum Potsdam （GFZ） and Jet Pro- pulsion Laboratory 0PL）. Compared with other published models in terms of equivalent water height distribution, our solution is consistent with those published by CSR, GFZ, JPL, Delft institute of Earth Observation and Space system （DEOS）, Tongji University （Tongji）, Institute of Theoretical Geodesy （ITG）, Astronomical Institute in University of Bern （AIUB） and Groupe de Recherche de Geodesie Spatiale （GRGS}, which indicates that the accuracy of WHU-Grace01s has a good consistency with the previously published GRACE solutions.

Monthly gravity field recovery from GRACE orbits and K-band measurements using variational equations approach

The Gravity Recovery and Climate Experiment（GRACE） mission can significantly improve our knowledge of the temporal variability of the Earth＇s gravity field.We obtained monthly gravity field solutions based on variational equations approach from GPS-derived positions of GRACE satellites and K-band range-rate measurements.The impact of different fixed data weighting ratios in temporal gravity field recovery while combining the two types of data was investigated for the purpose of deriving the best combined solution.The monthly gravity field solution obtained through above procedures was named as the Institute of Geodesy and Geophysics（IGG） temporal gravity field models.IGG temporal gravity field models were compared with GRACE Release05（RL05） products in following aspects：（i） the trend of the mass anomaly in China and its nearby regions within 2005-2010; （ii） the root mean squares of the global mass anomaly during 2005-2010; （iii） time-series changes in the mean water storage in the region of the Amazon Basin and the Sahara Desert between 2005 and 2010.The results showed that IGG solutions were almost consistent with GRACE RL05 products in above aspects（i）-（iii）.Changes in the annual amplitude of mean water storage in the Amazon Basin were 14.7 ± 1.2 cm for IGG,17.1 ± 1.3 cm for the Centre for Space Research（CSR）,16.4 ± 0.9 cm for the GeoForschungsZentrum（GFZ） and 16.9 ± 1.2 cm for the Jet Propulsion Laboratory（JPL） in terms of equivalent water height（EWH）,respectively.The root mean squares of the mean mass anomaly in Sahara were 1.2 cm,0.9 cm,0.9 cm and 1.2 cm for temporal gravity field models of IGG,CSR,GFZ and JPL,respectively.Comparison suggested that IGG temporal gravity field solutions were at the same accuracy level with the latest temporal gravity field solutions published by CSR,GFZ and JPL.

Response of Indonesian mineral supply to global renewable energy generation:Analysis based on gravity model approach

The captivating surge of energy transitions in the major industrialized nations has elevated the global demand for critical minerals.The demand pattern has enabled mineral-abundant emerging economies like Indonesia to enter the international market by exporting mineral goods.Accordingly,we investigate the Indonesian mineral export supply's response to the renewable energy production of the 18 clean energy-generating countries,considering crude oil and mineral prices,exchange rates,and economic growth of the resource and importer countries from 1990 to 2020.In doing so,we apply the Poisson Pseudo-maximum Likelihood(PPML)approach to measuring the panel gravity model for mineral exports in Indonesia.As a result,we observe a significant response of Indonesia's mineral export supply to the renewable energy generation of the 18 mineral importing countries.Besides,mineral and crude oil prices are insignificant,whereas the importer countries'exchange rates and income growth positively influence Indonesia's mineral export growth.However,Indonesia's income factor negatively affects its mineral export supply.Finally,we validate our results using an alternative estimator,the Driscoll-Kraay robust standard error estimation technique.Therefore,our findings suggest implementing Indonesia's existing mineral policy to produce finished mineral goods to materialize the worldwide vision of energy transitions toward a crossroad of net-zero emissions by the middle of the current century.

空间交互作用中的距离影响及定量分析

对地理学研究中空间交互问题的距离衰减现象进行描述和分析,并总结重力模型的求解方法。首先,大部分空间交互都受到距离衰减效应的影响,距离衰减函数定量表示交互中距离的作用。对比幂律、指数等多种形式的距离衰减函数,认为幂律形式能够更好地刻画距离影响的本质特征,并且可以在不同交互中进行比较,其对应的交互模型即为在地理学和区域经济学中广泛应用的重力模型。然后,在重力模型的基础上,总结解析法和模拟法两大类基于给定交互矩阵和距离矩阵定量计算距离衰减函数及衰减系数的方法。由于难以先验确定交互公式中节点规模的数值,因此拟合重力模型,同时估计距离衰减系数,是应用重力模型的恰当方式。

基于GRACEKBRR数据的动力积分法反演时变重力场模型

基于动力积分法恢复了一组60阶的时变重力场模型WHU-Grace01s,且在位系数解算过程中仅使用KBRR数据.通过与CSR、GFZ和JPL发布的Release 05模型的阶方差和位系数误差谱对比可知,WHU-Grace01s模型在高阶次部分的阶方差较小,且对轨道共振现象不敏感.将WHU-Grace01s时变重力场模型与CSR、GFZ、JPL、DEOS、Tongji、ITG、AIUB和GRGS等8家机构发布模型通过相同的滤波处理,获得了全球地表质量变化的时空分布,从结果可以看出:各个模型计算的时变信号在空域上分布十分接近,且WHU-Grace01s模型计算的太平洋中心和撒哈拉沙漠区域的质量变化较小;对比几个典型质量变化区域,WHU-Grace01s模型和JPL模型计算的长江流域和珠江流域时变信号呈强相关,其相关系数分别为0.948和0.976,且与上述8个模型计算的两个流域时变信号的相关系数均达到0.9以上;在南极区域和格陵兰岛,WHU-Grace01s模型和其他各个模型均能反映区域冰川质量的积累或消融,且各模型计算获得的长期趋势变化结果相当.研究结果表明,WHU-Grace01s模型和国内外已发布机构模型具有很好的一致性,且受到轨道共振影响较小.

基于CCD的激光测距机光轴平行性检测

提出了一种利用CCD器件检测激光测距机光轴平行性的方法,利用CCD和图像采集卡组成的图像采集系统对激光测距机瞄准系统十字分划像和发射的激光光斑进行采集,通过图像处理技术对采集到的图像进行处理,并确定激光光斑中心和十字分划中心坐标,即可获得激光测距机的光轴平行性误差。该方法能够实时、定量地检测光轴偏差,检测精度高,操作简单,有效地解决了传统方法只能定性地估算误差,人眼主观判断误差较大等问题。

基于重力卫星数据监测地表质量变化的三维点质量模型法

利用卫星重力测量手段监测全球质量变化取得了巨大成功,本文基于牛顿万有引力定律在三维空间直角坐标系中导出利用重力卫星观测数据监测全球质量变化的三维点质量模型法,该方法可直接利用重力卫星的轨道和星间观测数据或时变重力场模型计算全球质量变化,由于利用卫星观测数据计算地表质量变化的向下延拓过程以及观测数据噪声的影响,需要采用合适的空间约束方程或正则化技术对解算结果进行约束或平滑处理.利用合成全球质量变化模型模拟一个月的GRACE双星轨道和星间距离变率数据计算全球质量变化,对三维点质量模型法进行分析验证,采用零阶Tikhonov正则化技术处理病态问题.结果表明,三维点质量模型法可有效用于重力卫星观测数据监测全球质量变化,为利用重力卫星观测数据监测全球质量变化提供一种可选的途径.

顾及多方向观测值权比反演地球重力场的动力积分法

考虑到不同坐标系下各个方向观测值对反演地球重力场的频谱贡献不同,建立了顾及多方向观测值权比的动力积分法,并利用该方法反演了高精度的GOCE HL-SST卫星重力场模型.首先,分析了不同坐标系下各个方向观测值与地球重力场信息的响应关系,其中惯性系(IRF)下X、Z方向的观测值分别对扇谐系数、带谐系数最为敏感,Z方向的解算精度在全频段均略高于X、Y方向;地固系(EFRF)下各个方向的独立解算精度均与能量守恒法的解算精度相当;局部指北坐标系(LNOF)下X、Z和Y三个方向的解算精度依次递减,且Y方向在47阶附近有明显"驼峰"现象.其次,比较了不同坐标系下顾及三个方向观测值权比的加权解算模型,其中加权联合解算模型精度在20至70阶次均明显优于等权解算模型,在带谐项和共振阶次精度提升明显,且LNOF下的加权联合解算精度要优于IRF和EFRF.最后,比较了GOCE和CHAMP卫星的模型解算精度,采用本文计算方法,仅利用2个月GOCE轨道观测值解算的模型精度优于包含更长观测时段信息的AIUB-CHAMP01S和EIGEN-CHAMP03S模型,且略优于ASU-GOCE-2months模型.

基于能量守恒方法恢复地球重力场模型

基于低轨卫星精密轨道和非保守力加速度数据给出了统一求解偏差、尺度、漂移及位系数的能量守恒方法。该方法不需要任何未知数初始值,避免了单独标校加速度时受先验重力场模型的影响。利用GRACE卫星102天数据恢复了89阶次重力场模型SWJTU-GRACE01,并与EGM96、EIGEN2、EIGEN-CHAMP03S、GGM02S、EIGEN-CG01C模型进行了比较。结果表明,SWJTU-GRACE01模型精度优于相同阶次的EGM96、EIGEN2、EIGEN-CHAMP03S,在低阶位系数上与GGM02S具有较好的一致性。

基于客货运量的新疆城市等级体系分析

应用集中系数、区域非均衡系数、改进的重力模型对客货运量分别进行评价,并通过定性的方法对结果进行修正,得出结论:(1)新疆城市客货运的集中程度差异明显;(2)新疆客货运输的节点不一致,呈现出不同的变化趋势;(3)目前新疆基本形成以乌昌地区为中心,以"奎屯-乌苏"双核城市和喀什为次中心,以石河子、博乐、库尔勒、阿克苏、阜康为区域中心,其他城市为区域次中心的城市等级体系.

基于重力模型的中国城市体系空间联系与层域划分

新中国成立以来,中国大陆城市体系空间格局发生了深刻的变化。传统的城市体系空间联系主要从人流、物流、技术流、信息流、金融流进行数据的收集和分析,也有运用图论原理进行Rd链分析。近来,随着社会主义市场经济的迅速发展,城市之间的联系变得异常复杂、数据不易得到。本文试图运用重力模型方法对中国城市间的空间联系强度进行定量计算,据此刻画中国城市体系的空间联系状态和结节区结构。从研究结果看,所得结论与实际情况基本吻合。

利用GOCE卫星轨道数据恢复地球重力场模型的方法

欧空局早期公布的时域法和空域法解算的GOCE模型均采用能量守恒法处理轨道数据,但恢复的长波重力场信号精度较低,而且GOCE卫星在两极存在数据空白,利用其观测数据恢复重力场模型是一个不适定问题,导致解算的模型带谐项精度较低,需进行正则化处理。本文分析了基于轨道数据恢复重力场模型的方法用于处理GOCE数据的精度,对最优正则化方法和参数的选择进行了研究。利用GOCE卫星2009-11-01—2010-01-31共92d的精密轨道数据,采用不依赖先验信息的能量守恒法、短弧积分法和平均加速度法恢复GOCE重力场模型,利用Tikhonov正则化技术处理病态问题。结果表明,平均加速度法恢复模型的精度最高,能量守恒法的精度最低,短弧积分法的精度稍差于平均加速度法。未来联合处理轨道和梯度数据时,建议采用平均加速度法或短弧积分法处理轨道数据,并且轨道数据可有效恢复120阶次左右的模型。Kaula正则化和SOT处理GOCE病态问题的效果最好,并且两者对应的最优正则化参数基本一致,但利用正则化技术不能完全抑制极空白问题的影响,需要联合GRACE等其他数据才能获得理想的结果。

局部扰动引力逼近的改进虚拟压缩恢复法研究

将改进的虚拟压缩恢复法应用于扰动引力的逼近问题,与点质量法的比较表明,改进的虚拟压缩恢复法和点质量模型对扰动引力的逼近精度和逼近速度相当。

河南省公路空间运输联系的时空演变分析

以公路客运量、货运量以及熵值法计算下的复合流量作为测度指标,综合运用集中系数、非均衡系数、重力模型、最大引力连接线等方法与模型对河南省18个省辖市城市节点性与空间联系的时空演变特征进行分析.研究表明:1从时间上看,2003—2013年,河南省18个省辖市公路客货运集中程度差异显著,客运量集中程度比较明显而货运量相对分散,2008年以后两者都表现出比较稳定的集中态势.非均衡系数逐年增加,河南省整体客货运呈现出先分散后集中的发展特征.2从空间特征上看,以客运量测度的河南省城市节点空间联系形态呈现以郑州为核心的"中心-外围"辐射状特征,相反以货运量测度的城市中心节点性较弱且分散.以复合流量测度的河南省城市节点中心性也较分散,除2008年表现出以郑州为核心的"中心-外围"状外,其余年份城市中心节点性较弱且相对分散.

γ能谱滤波方法比对研究

对现行各种γ能谱滤波方法进行比对研究,发现各种滤波方法对能谱数据均有一定压缩与展宽;能域滤波时,谱线展宽增加重峰出现几率;频域滤波时,应注意滤波器及其参数的选取;小波变换能很好地保持信号的高频突变成分不受破坏,相比较而言,改进阈值方法能很好地保留硬阈值与软阈值的优点,适于弱峰的检测.针对重心法滤波器的不足,提出一种1倍标准差检测滤波算法,该方法能很好地保留能谱突变成分,维持谱峰净面积基本不变,对平台滤波效果等同于5点重心法,且算法简单.

重心法计算重积分

介绍了计算重积分问题的一种方法——重心法.在对一些二重积分或三重积分的计算中,此法有时更为简便有效.

利用平均加速度法恢复GOCE地球重力场模型

将非保守力残余加速度参数作为未知参数与位系数整体求解，利用GOCE卫星2009—11-01--2010-01—31日的精密轨道数据，基于平均加速度法恢复了120阶次的重力场模型GOCE—AAA01S。结果表明：利用12阶多项式解算的模型精度最高，并且阶数的增加或减少均会降低恢复的重力场模型的精度；在120阶次的大地水准面误差约为±6．8em，在6～120阶次内GOCE—AAA01S的精度优于EIGEN．CHAMP03S，在102阶次以后GOCE—AAA01S的精度低于EGM96。文中未考虑极空白的影响，所恢复的重力场模型位系数的带谐项精度偏低。