The motion of a continuously operating reference station is usually dominated by the long-term crustal motions of the tectonic block on which the station is located. Monitoring changes in the coordinates of reference stations located at tectonic plate boundaries allows for the calculation of velocity fields that reflect the spatial and temporal characteristics of the region. This study analyzes the spatiotemporal relationships of regional reference frame points with GNSS data from 25 reference stations in Sichuan, China, from 2015 to 2021. The common mode errors are extracted and eliminated by principal component analysis. A time series function model is developed for the reference stations and their constituent baselines for calculating the velocity field. Subsequently, the spatiotemporal characteristics of the regional reference frame in Sichuan is analyzed by a stochastic model. The results show that the influences of the common mode error on the horizontal and vertical directions of the reference stations is 2.5 mm and 4.3 mm, respectively. Generally, the horizontal motion of the reference stations in the Sichuan region tends to be in the southeast direction and the vertical motion trend is mainly uplifting. The east–west and vertical components of the baseline tend to be shortened, and the random influence among the reference stations is larger in the north–south and east–west directions—0.39 mm and 0.54 mm, respectively. Polynomial functions are more appropriate for constructing the fitted random influence covariance model.

利用Helmert转换模型,首先对起算点先验坐标可能存在的粗差进行探测并剔除,其次依据剩余起算点坐标的相似变换构建最小约束条件,最后实现整网坐标框架的确定.选取中国境内及周边IGS站和陆态网GNSS基准站单周观测数据,采用IGS站ITRF2014坐标分别构建参数加权约束、最小约束、顾及IGS站先验坐标误差的Helmert模型约束,然后利用不同的基准约束平差方法获取整网坐标成果.实验结果表明,利用Helmert模型能有效削弱起算点坐标粗差对网形扭曲的影响,在一定程度上可提高区域参考框架的精度和可靠性.

The high-precision terrestrial reference frame, as the spatial benchmark for geodesy, is an important national infrastructure. However, due to the influence of nonlinear factors related to geophysical phenomena, the overall maintenance accuracy of the ITRF framework is still at the centimeter level. Therefore, accurately characterizing the true trajectories of linear motion, nonlinear motion, and geocentric motion of the reference station is the key to achieve the construction and maintenance technology of a millimeter level terrestrial reference framework. Based on long-term global and regional GNSS observation data, more Chinese geodesy scientists devoted much efforts to the maintenance of millimeter-level geodetic reference framework. The main contributions of this work included the followings: ①Dynamic maintenance of millimeter-level terrestrial reference frame;②Research progress on the method of maintenance of regional reference frame based on GNSS; ③The progress of CGCS2000 frame maintenance in millimeter level accuracy; ④Reprocessing and reanalysis of two-decade GNSS observation in continental China;⑤Research on current GNSS velocity field model and deformation in Chinese mainland;⑥The preliminary realization and evaluation of CTRF2020.

2021年5月22日,青海省玛多县发生M7.4级地震,地震对区域基准站造成了影响.本文收集了距震中400 km以内的青海省全球卫星导航系统(GNSS)连续运行参考站(CORS)的高频观测数据,以国际GNSS服务(IGS)站和陆态网为参考基准,分别采用静态模式和动态模式分析了震后地表三维形变.结果表明:站点位移量级随震中距的加大而呈现衰减趋势,其中距震中约35 km的江多站(JDUO)产生东偏南28.0 cm的永久性位移.整体来讲,地震对100 km内的震源区的影响表现为走滑型运动,与震源机制相吻合,区域运动特征整体表现为拉张运动,北西-南东(NW-SE)向拉张和北东-南西(NE-SW)向挤压.

Abstract Changes in the tropopause can explain regional and global weather and climate. In Tibet, there are few radiosonde stations, and the detection height is not high enough. Radio occultation (RO) data are insufficient because of the small regional scale, which is not conducive to the analysis of tropopause change. Moreover, in some middle and high latitudes, it was more difficult to identify the tropopause height from the temperature profile. In this study, an improved method has been developed for the inversion of the tropical tropopause based on a ground‐based global navigation satellite system (GNSS) network combined with reanalysis data. Using zenith tropospheric delay data from 49 GNSS reference stations in Tibet from January 2017 to December 2019, combined with ERA5 reanalysis, the tropical tropopause (TPH) was successfully inversed, its temporal and spatial distribution is analysed, and compared with ERA5‐derived TPH obtained by the temperature profile of the interpolated co‐site points. In more than 90% of cases, the difference between the two is <2 km. The root mean square of the tropopause difference detected by GNSS‐derived TPH and RO‐derived TPH was ±1.25 km; the accuracies were at the same level. By combining the tropopause obtained from ground‐based GNSS and that from space‐based RO, temporal and spatial changes in the tropopause were analysed. The tropopause in Tibet has a latitude‐zoning distribution with obvious unimodal seasonal changes. Monthly changes excluding seasonal variation indicate a slight downward trend from 2017 to 2019. At the same time, changes in the tropopause are closely related to those in weather and climate. The results of this study confirm that the combination of ground‐based GNSS and space‐based RO can realize long‐term, continuous, and full coverage monitoring of the regional tropopause. This expands the application possibilities of ground‐based GNSS.

2015年尼泊尔地震对珠穆朗玛峰高程的影响,近年一直受到全世界关注.2020年珠穆朗玛峰高程测量在珠穆朗玛峰及周边地区布设了高精度的全球导航卫星系统(global navigation satellite system,GNSS)形变监测网,收集了1999-2020年跨喜马拉雅山脉的32个连续运行参考站(continuously operating reference sta-tions,CORS)的GNSS连续观测数据.利用GNSS数据监测了珠穆朗玛峰周边地区地壳三维形变特征,定量获取了2015年尼泊尔强震对珠穆朗玛峰周边CORS同震位移,以及地震对区域地壳三维形变长期趋势的影响,特别是对该地区垂直形变的影响.研究结果表明,该区域地壳垂直形变由南至北跨喜马拉雅山脉呈明显的阶梯型分布特征;震后印度板块与欧亚板块存在加速汇聚趋势,导致震后地壳隆升速率同步增大.

针对珠峰区域南北坡复杂的地壳运动特征,提出通过分析全球卫星导航系统(GNSS)连续观测数据获得的高精度速度场及空间基线时间序列运动特征,来揭示该区域的运动趋势.结果表明:该区域自西向东表现出北东、东、东南的顺时针旋转趋势,区域西部的速率为36 mm/a、中部及东部速率为47 mm/a,同时得出不同时间跨度的结果具有较好的一致性和连续性的结论,基于无旋转地学板块运动模型(NNR-NUVEL-1A),获得了扣除整体板块运动后的珠峰区域速度场,反映出印度板块以北东方向、角度20～30°,35 mm/a的速率推挤欧亚板块,在穿过喜马拉雅主逆冲带后,速率减小为27 mm/a.同时从珠峰区域南北坡基准站间的空间关系运动特征得出,超过66％的基线分量在南北方向表现为缩短、65％在东西方向表现为拉伸且具有明显的方向性,63％的基线长度表现为缩短趋势,且此特征在北坡、南坡及跨断裂带基线中均表现明显.通过速度场和基线空间运动关系两方面均得出,珠峰区域南北方向运动特征为凝聚;东西方向为拉伸.

The observation of GNSS monitoring in mountain area is often severely restricted by tropospheric delay, resulting in the reduction of positioning accuracy. In this paper, a constraint method for the prior information of tropospheric delay at ground points is put forward to realize the fast and high-precision double differenced observation of the peak. This method can make full use of the augmentation information of tropospheric delay of long-distance ground station, the observation duration decreased notably, increase the stations range of mountain monitoring, so as to reduce costs of mountain measurement task. In this paper, the applicability is verified by the spatio-temporal characteristics of observation duration, baseline distance and number of ground stations. The experimental results indicate that takes the high-precision tropospheric delay into account as prior constraints, acquired by long-time GNSS observation at ground stations, which can weaken the influence of tropospheric delay residuals efficiently induced by large heights different between different stations and improve success rate of ambiguity fixing, and can achieve tropospheric delay parameter estimation and fast high-precision positioning of peak monitoring points. Compared with the unconstrained method, the accuracy of each coordinate component is improved after the troposphere prior constraints, and the accuracy of the elevation direction is improved significantly.

针对区域参考框架受地质构造活动,区域水平运动具有同向性与异向性混叠的复杂特征,造成局部区域参考框架难以有效维持的问题,该文提出顾及板块运动异向性与局部稳定性的区域参考框架维持思路,该方法引入了局部特征点采用最小约束的方法削弱不同板块的相对运动造成区域参考框架的形变影响.以我国西南某区域的基准站网数据为实验对象,结果表明:该方法较传统方案可较好地减少板块运动对区域参考框架的影响,最大限度地保持了与原始观测量图形属性及已有图形空间关系的相似性,实现了区域参考框架坐标变化的平稳过渡.

Due to the short peak observation time of global navigation satellite systems (GNSS), the accuracy of the tropospheric delay estimation and the positioning are poor. In this study, a rapid GNSS network solution for mountainous regions is presented. The high-precision tropospheric delay at ground points is obtained from long-term ground observation data and used as a priori constraint in the double-difference equation of short-time synchronous peak observations to realize rapid and high-precision positioning. Chinese mountain survey networks with large elevation gradient (1000~2000 m) were selected for the experimental verification of the proposed method. The results show that the rapid peak positioning method weakened the effect of the residual tropospheric delay caused by the elevation difference, significantly improving the accuracy and reliability of the results. The positioning accuracy of the peak in upward direction was better than 1.1 cm, which meets the requirements of rapid short-span (~1 h) high-precision monitoring and achieves 24 h positioning accuracy. Compared with the traditional solution strategy, the precision of the method with respect to the north (N), east (E), upward (U), and zenith tropospheric delay (ZTD) significantly improved. The accuracy of U improved by more than 47%. Therefore, based on the high accuracy and reliability, information of ground stations can be fully utilized to significantly reduce the peak observation time and the operation costs of surveys in mountain regions.

随着北斗卫星导航系统组网成功,分析北斗系统的定位性能及在区域参考框架维持中的应用具有重要意义.本文以陕西和西部某区域北斗基准站为基础,从卫星数据质量、覆盖能力、网解模式和PPP解模式分析了北斗三号卫星定位性能及在区域高精度参考框架维持的可行性与可靠性.结果表明:BDS-3卫星的位置精度衰减因子(PDOP)优于BDS-2卫星;BDS-3和BDS-2卫星在网解和PPP解的BDS-3定位性能优于BDS-2,网解BDS-3较BDS-2在平面与高程方向精度分别提升2.4％、20.1％;BDS-3 PPP收敛速度优于BDS-2,提高了快速定位的精度;基于BDS-3构建的毫米级高精度区域参考框架的可靠性与GPS在同一水平,平面差异量优于3 mm,垂直差异量级优于7 mm;基于BDS的PPP解平面方向平均差异优于9 mm,垂直方向平均差异优于18 mm,可快速识别区域基准站的变化量进行区域参考框架维护;融合BDS-3维持区域参考框架,可提升区域参考框架维持的可靠性.

以东北地区2005～2018年近14 a的中国地壳运动观测网络数据为基础,采用三角划分方法构建相邻区域的基线时间序列,从频谱特征、残余共模误差、空间相对运动规律3个方面进行时空特征分析.结果表明,基线各分量的周期性影响主要以年周期和半年周期为主;基线之间的残余共模误差在平面方向的影响约为1.14 mm,垂直方向的影响最大为3.17mm;平均随机影响在东西方向最大;基线水平分量在空间尺度上逐年缩短,以北东方向的基线为主,在南北分量尤为明显,且在近海和内陆地区都有较明显的缩短趋势.

In order to achieve the goal that China and Nepal jointly announce the height of Mount Qomolangma, China has carried out the height measurement campaign of Mount Qomolangma from 2019 to 2020, and completed the summit survey on May 27, 2020. For the first time, airborne gravity survey was conducted in the north region of Mount Qomolangma and ground gravity data at the summit was collected, and the local gravimetric quasigeoid model and the geoid undulation of the summit in the International Height Reference System (IHRS) were determined. A variety of advanced measuring equipment, especially domestic measuring instruments played a full and active role in 2020 campaign. By means of the cross validations between multiple geodetic techniques and the strict checking computations, the accuracy and reliability of the results of 2020 campaign were ensured. Finally, China and Nepal collaborated on the data processing and jointly determined that the orthometric height (altitude) of the snow surface of the summit of Mount Qomolangma is 8 848.86 m.

基准站受构造运动与非线性因素的影响,如何构建高精度、现势性强的精细区域框架是位置服务与形变分析的的关键.笔者提出顾及基准站坐标动态特性与稳定性的区域框架构建方法.以我国西部与东部某城市的多年连续运行基准站数据为例进行试算比对,试验结果表明:该方法是可行的,较好地顾及了基准站的坐标特性与非线性影响,考虑了基准站的垂直运动规律,可构建高精度的区域基准,可发现区域基准的微动态变化.

针对常规个人计算机(PC)存贮与计算效率低,无法满足大规模全球卫星导航系统(GNSS)基准站网高效数据计算要求的问题,提出利用云计算技术实现高效的计算:采用云计算技术搭建计算平台,安装GAMIT/GLOBK软件系统进行大规模GNSS基准站网数据处理,并与PC机解算进行对比分析.结果表明:云计算平台上同时运行6个以上任务时,效能明显优于PC机;且随着任务数量的增多,效能显著提高,当软件打开文件数量达最大荷载时,云计算平台仍稳定正常运行,且计算结果正确可靠.

Employing the merged quasi-geoid, we analyses the causes of systematic errors in modelling of quasi-geoid of neighbouring areas in the paper, and the efficient method is introduced to improve the accuracy of quasi-geoid. First, the systematic error is weakened with the moving window method applied to established quasi-geoids in two adjacent regions, and the accuracy of the merged quasi-geoid in the stitching region is checked using the measured GPS benchmark data; Second, the whole quasi-geoid is recomputed with data obtained from two adjacent regions if the accuracy of the quasi-geoid obtained from the first step in the stitching region is low; Finally, the quasi-geoids in two adjacent regions are recomputed respectively using GPS benchmark data of own region and adjacent region with the same solution if the accuracy of whole quasi-geoid obtained from the second step also is low. Actual data sets from Sichuan Province and Chongqing City are employed to test the moving window method. It is shown that the quasi-geoid models with high resolution and accuracy were obtained.

影响GNSS数据质量因素较多,多路径效应是其中重要的因素,本文结合多路径效应数据处理模型与方法,以实测GNSS数据为基础,针对多路径效应的影响相关性进行了研究分析.结果表明:对于连续长时间观测数据而言,多路径效应具有一定的重复性与周期性;由气象变化因素引起的多路径效应可通过数据处理模型有效削弱,由遮挡引起的多路径效应中周跳的分布状态是影响数据质量的重要参考指标;多路径效应与数据质量之间相关性较弱,并呈现一定的随机性,多路径数值大小与定位结果精度之间没有必然联系,仅以多路径、数据有效率指标评定数据质量与定位结果存在一定的不合理性.

Because the regional land quasi-geoid has the irregular and unequal precision ,this paper proposes a new move window method to merge the quasi-geoid ,which takes into account the regional attribute . Taking the southwest China region's quasi-geoid as the case ,this paper demonstrates the feasibility and reliability of the method ,and the results indicate that ,the algorithm can enhance the control effect of relative high precision quasi-geoid ,and effectively weaken the systematic errors .The merging accuracy is better than the fitting method w hile the algorithm model is rigorous and fast in computional efficiency .

In connection with the effection of the local terrain slope factors and extreme value to terrain area calculation,a new method that considering of slope factors and extreme value is proposed.The surface area theory and errors are analyzed.Finally the typical two region's data of west China are used experiment analysis.The results indicate that the algorithm enhance the terrain fitting,on the macro,the graphic property is similar with the regular grid of cross-diagonal method.The deduce area errors formula indicated that the terrain surface area calculation is more reliable in considering the slope factors and extremevalue.

结合图形学思想,提出基于三角剖分与方向线拼接的算法构建高精度坐标转换格网模型.以中国东部与南部某城市数据为例进行比较,结果表明,该方法能发挥图形结构在已知点选取中的作用,有效控制误差传递,获取很好的拼接效果,且各三角形子区互不影响,拼接区不存在拼接缝,验证了该方法的可行性与可靠性.