Earth Gravity Field Recovered from CHAMP Science Orbit and Accelerometer Data

The earth gravity field model CDS01S of degree and order 36 has been recovered from the post processed Science Orbits and on-board accelerometer data of GFZ’s CHAMP satellite. The model resolves the geoid with an accuracy of better than 4 cm at a resolution of 700 km half-wavelength. By using the degree difference variances of geopotential coefficients to compare the model CDS01S with EIGEN3P, EIGEN1S and EGM96, the result indicates that the coefficients of CDS01S are most close to those of EIGEN3P. The result of the comparison between the accuracies of geopotential coefficients in the above models, indicates that the accuracy of coefficients in CDS01S is higher than that in EGM96.The geoid undulations of CDS01S and GGM01C up to 30 degrees are calculated and the standard deviation is 4.7 cm between them.

Progress in satellite gravity recovery from implemented CHAMP,GRACE and GOCE and future GRACE Follow-On missions

Firstly, the Earth＇s gravitational field from the past Challenging Minisatellite Payload （CHAMP） mission is determined using the energy conservation principle, the combined error model of the cumulative geoid height influenced by three instrument errors from the current Gravity Recovery and Climate Experiment （GRACE） and future GRACE Follow-On missions is established based on the semi-analytical method, and the Earth＇s gravitational field from the executed Gravity Field and Steady-State Ocean Circulation Explorer （GOCE） mission is recovered by the space-time-wise approach. Secondly, the cumulative geoid height errors are 1.727 × 10^-1 m, 1.839 × 10^-1 m and 9.025 × 10^ -2 m at degrees 70,120 and 250 from the implemented three-stage satellite gravity missions consisting of CHAMP, GRACE and GOCE, which preferably accord with those from the existing earth gravity field models involving EIGEN-CHAMP03S, EICEN-GRACE02S and GO_CONS GCF 2 DIR R1. The cumulative geoid height error is 6.847 × 10 ^-2 m at degree 250 from the future GRACE Follow-On mission. Finally, the complementarity among the four-stage satellite gravity missions including CHAMP, GRACE, GOCE and GRACE Follow-On is demonstrated contrastively.

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.

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.

Observation on Height Changes of Chinese Tide Gauges by GPS

The height changes of tide gauges directly influence sea level observation. For research of sea level variation in large region or globe, the land vertical displacement must be considered. Two sessions of GPS and absolute gravity observations in 2001 and 2003 are used to determine the horizontal and vertical motion of China coast in ITRF2000 and Eurasia frame. The difference between results of continuous observation and periodic observation is discussed.

GPS-Meteorology Network in Wuhan Region

在在武汉区域的 GPS 气象学网络的学习有三个方面。第一是在相对系数为是 99.97 的最后的位置推算历和超速的位置推算历之间的 GPS 可降水蒸汽的比较，根平均数摆平是 0.048 公里。超速的位置推算历能被用来为即时预言得到 GPS 可降水蒸汽，这能被结束。第二是 GPS 车站的可降水蒸汽的比较，在武汉区域的水汽的分发被获得。在一个降雨过程的 GPS 可降水蒸汽和降雨的变化被比较并且分析。GPS 可降水蒸汽的变化能反映并且预言降雨的过程。

Invitation for ISGG2018

(http://isgg2018.csp.escience.cn/dct/page/1)Dear friends and colleagues,Many of the attendees of last year’s ISGG2016 conference found it to be deeply meaningful.At this conference,they shared recent developments in the field of geodesy and geodynamics around the conference theme.In order to further enhance the application of geodesy within geoscience,another conference,the Interna-

Invitation

Dear Colleagues, As Chairman of the Conference Committee, it is my great pleasure to invite you to participate in the International Symposium on Geodesy and Geodynamics （ISGG 2016）. This international academic symposium will be hosted jointly by the China Earthquake Administration, the International Association of Geodesy （lAG）, and the National Natural Science Foundation of China and organized by Institute of Seismology of the China Earthquake Administration.

Invitation for ISGG2018

Dear friends and colleagues,Many of the attendees of last year＇s ISGG2016 conference found it to be deeply meaningful.At this conference,they shared recent developments in the field of geodesy and geodynamics around the conference theme.In order to further enhance the application of geodesy within geoscience,another conference,the International Symposium on Geodesy and Geodynamics-Tectonics,earthquake and Geohazards （ISGG 2018）, is slated to be held at Kunming, China, from July 30 to August 2, 2018. As the chairman of the conference, it is my honor to invite friends old and new to this new conference. We will meet together in Kunming to share our research and discuss the applications of geodesy in geoscience, geohazards, and other fields and to discuss the future direction of geodvnamics.

车载三天线GNSS的直接法定姿及精度评估

针对移动测量系统对载体姿态的需求,对车载三天线全球卫星导航系统（global navigation satellite system,GNSS）的直接法定姿进行了研究。分析了定姿的原理,给出了姿态解算公式,并提出一种简便的方法确定航向角的象限,解决了航向角的多值性问题。为了评估该方法的精度,利用车载的三天线GNSS进行了动态实验,采集了动态观测数据,利用直接法对观测数据进行了姿态解算,并用同车搭载的一套高精度惯性导航系统（inertial navigation system,INS）给出的姿态参考值对三天线GNSS定姿的精度和可靠性进行了评估。结果表明,三天线GNSS直接法定姿精度高、可靠性好,并具有计算简便,可避免奇异性问题等优点。

利用重力等位面特性进行地球重力场模型评价

提出了一种基于大地水准面等位面特性的地球重力场模型优劣评价方法。通过取任一重力大地水准面为参考面,计算不同地球重力场模型在该面上的重力位标准差,以此作为不同模型相对优劣的评价指标。利用该方法对不同地球重力场模型以及同一重力场模型在不同区域的精度进行了评价。结果表明：EGM96、OSU91A模型的大地水准面高精度分别为±11.1cm、±14.3cm,说明EGM96要优于OSU91A,EGM2008、EIGEN-6C4模型的大地水准面高精度分别为±8.8cm、±8.9cm,说明该两个模型的精度相当,与已有研究结果一致,表明本文方法的有效性与适用性。进一步研究结果显示,对于全球大地水准面,EGM2008和EIGEN-6C4模型的大地水准面高精度分别为±11.3cm和±14.1cm,即在厘米级精度上EGM2008略优。

一种基于属性值变化程度定权的聚类算法

针对经典K-means聚类算法以欧氏距离作为相似度判断法则进行聚类划分,而未考虑聚类对象的各属性值对聚类划分的影响程度存在差异的问题,该文提出了一种基于属性值变化程度定权的聚类算法。通过采用Iris dataset数据进行实验,该算法相对于其他聚类算法获得了更好的聚类效果,且该算法适用于生物物种分类、遥感影像识别等工作领域,能提高聚类运算的精准度。

Trend of China land water storage redistribution at medi- and large-spatial scales in recent five years by satellite gravity observations

卫星严肃使命提供了的优雅(严肃恢复和气候实验) 学习土地的一个新方法在最近的年里在 medi 空间、长空间的规模浇集体再分配。我们在 2003 ～ 2007 期间用优雅观察在中国估计大陆人水团再分配。结果随增加显示出一些大区域或土地的减少在 Xinjiang Uygur 自治区域在中央北区域，西藏的高原，三个峡区域， Qinghai，四川和 Gansu 省相遇的地方，和 Altun 山区域浇集体存储。在开始的二个区域，水(冰) 集中，是明显的存储正在减少。在以 2.4 cm/a 等价物的线性率的中央北区域减少的水质量浇高度，在五年的时期期间每年等于到 52 亿立方的米，并且浇集体弄空在 Hebei 省是 ∼45 亿立方的米每滥用的地下的水的年每在一样的时期，它与一般水准一致的年浇 40 亿立方的米的集体弄空在最近 Hebei 省估计的 30 年浇资源局。而且，优雅能检测 ∼ 的水团累积在散布超过大约 12 万的区域以内的 5 厘米相等的水高度由于三峡摆平公里在 2003 年 6 月的水坝建设。我们也发现 ∼ 的水团获得在 Qinghai，四川和 Gansu 省相遇的区域的 1.1 cm/a。这显示这些区域的气候在最近的年里一直在变得逐渐地潮湿。