Removing attitude-related variations in the line-of-sight for kinematic GPS positioning

We are presenting a method for removing attitude-related variations (ATTRVs) in dynamic 1 Hz GPS positioning. The ATTRVs are separated into vertical and horizontal components. These result from the translational and rotational motions of the vehicle, which is a marine research vessel in our case. We have developed new observation equations that use corrected pseudoranges and carrier phases to account for ATTRVs. In the present contribution, we are only focusing on the vertical signals. These modeled ATTRVs are included as corrections in the line-of-sight (LoS) to each GPS satellite in the RINEX data sets using a new software called RNXATTCOR. Precise IGS sp3-orbits are used as inputs together with precise lever arm coordinates of the onboard GPS antennas, observations from the marine inertial navigation system and a priori 3D position of the vessel. The corrected RINEX data sets are then processed using kinematic processing or sequential processing in Precise Point Positioning (PPP) mode. The reduction of the standard deviation from a running mean in the final processed GPS time series is about 95%. The current method is being proposed for marine geodesy science applications such as along-track calibration/validation of altimetry products, and also for applications related to offshore kinematic high precision GPS positioning such as drilling, offshore platforms stability, marine pipeline positioning, earthquake monitoring and tsunami detection.     

超站式集成测绘系统STGPS的研究

介绍了超站式集成测绘系统STGPS的研究思想、研究目标、系统构成和功能;讨论了坐标转换和测绘基本服务问题;提出了无需作加密控制的即用即测作业模式。     

Monitoring the quality of GPS station coordinates in real time

This paper evaluates various statistical process control algorithms for monitoring the quality of GPS station coordinates in real-time kinematic applications. Real-time detection of small but persistent shifts in GPS coordinates is critical for applications requiring automatic and reliable results in deformation monitoring. Examples include monitoring of dams, high-rise buildings, bridges, tectonic movements, landslides and so on. The conventional cumulative sums (Cusums), the robustified and self-starting Cusums, the adaptive Cusum and the exponential weighted moving average are some of the control charts applied to real-time-kinematic (RTK) data in field experiments. All control charts have been evaluated for their effectiveness in detecting an actual but intentional deformation shift of at least 0.5 standard deviations from a target mean. The observations used in testing these control charts had initially been assumed to be independent and follow a normal distribution, but later, their serial correlation was taken into consideration. These results show that the self-starting but robustified Cusums as well as the exponentially weighted moving average charts are suitable and efficient tools in monitoring quality in the RTK data. All presented control charts are implemented as modules in a software package being developed by the Technical University of Crete.     

差分GPS水下立体定位系统

差分GPS水下立体定位系统包括GPS差分基准站、GPS浮标、水下收发机、船基控制中心四部分。差分基准站提供GPS差分改正,实现浮标内置GPS高精度实时定位。GPS浮标完成水上和水下的集成,检测水下收发机发射的定位信号并测量信号到达的时间,同时将各种数据发送到船基控制中心。船基控制中心接收各个浮标的数据后实时解算水下收发机的位置,同时将结果发送给水下收发机。本文首先对系统的总体构成和各个部分的功能进行了介绍,然后详细推导了系统定位算法,最后结合系统试验情况给出了系统试验精度统计结果。     

Local datum definition and geodetic network positioning using global navigation satellite systems

The problem of datum definition as applied to local-area geodetic networks is investigated using data collected from global navigation satellite systems (GNSS). It is shown that the process of double differencing makes the model more sensitive to computational errors that reduce the ability of the satellites alone to control the translation component of the datum definition, and as a result additional regularization is required. Traditionally, datum definition has been accomplished by constraining one station to set coordinates. Alternative regularization strategies are analysed in terms of their effects on positioning and ambiguity resolution. In doing so, processing strategies are developed which can improve the quality of global positioning system (GPS)-based position solutions in geodetic network applications of limited spatial extent, such as high-precision engineering and deformation monitoring networks.     

Automatic and Online Detection of Small but Persistent Shifts in GPS Station Coordinates by Statistical Process Control

This paper describes algorithms to detect sudden and persistent changes of small magnitude in the GPS baseline solution vectors or station coordinates. The aim of the algorithms is to monitor and control the quality of GPS measurements for critical real-time and crustal deformation applications using statistical process control. Quality control is a major problem in GPS, especially where real-time, automatic, and reliable positioning is needed, such as in the case of the GPS crustal deformation-monitoring network (GEONET) of Japan. To monitor the quality of baseline solutions the statistical techniques of Shewhart and cumulative sum charts are implemented. GPS data from GEONET, analyzed by the National Research Institute for Earth Science & Disaster Prevention (NIED), are used to test and evaluate the process control algorithms. ? 2001 John Wiley & Sons, Inc.     

Improving carrier-phase ambiguity resolution in global GPS network solutions

Integer carrier-phase ambiguity resolution is one of the critical issues for precise GPS applications in geodesy and geodynamics. To resolve as many integer ambiguities as possible, the ‘most-easy-to-fix’ double-difference ambiguities have to be defined. For this purpose, several strategies are implemented in existing GPS software packages, such as choosing the ambiguities according to the baseline length or the variances of the estimated real-valued ambiguities. Although their efficiencies are demonstrated in practice, it is proven in this paper that they do not reflect all effects of varying data quality, because they are based on theoretical considerations of GPS data processing. Therefore, a new approach is presented, which selects the double-difference ambiguities according to their probability of being fixed to the nearest integer. The probability is computed from estimates and variances of wide-lane and narrow-lane ambiguities. Together with an optimized ambiguity fixing procedure, the new approach is implemented in the routine data processing for the International GPS Service (IGS) at GeoForschungsZentrum (GFZ) Potsdam. Within a sub-network of about 90 IGS stations, it is demonstrated that more than 97% of the independent ambiguities are fixed correctly compared to 75% by a commonly used method, and that the additionally fixed ambiguities improve the repeatability of the station coordinates by 10–26% in regions with sparse site distribution.     

IGS服务数据专用FTP客户端设计与实现

近年来,GPS的应用日益广泛,在精密单点定位解算、GPS基线解算、站坐标解算、地球电离层研究实验等应用中,需要大量IGS站点观测数据及精密产品信息,下载工作繁琐且耗时。为了提高IGS数据下载效率,实现智能化下载,作者研制了基于WinInet API的IGS服务数据专用FTP客户端。实验测试结果表明:该软件操作简单,能快速准确地实现批量下载功能。     

用距离交会算法进行测点坐标改正

在野外数据采集过程中时常会遇到由控制点数据错误产生测点位置错误问题。对此类问题,本文总结分析了其可能出现的多种情况,归纳出了错误的类型。提出了采用距离交会算法对测点坐标进行改正的新方法,导出坐标数据改正的数学模型,总结出了用一种数学模型解决控制点坐标有误甚至无控制点坐标等多种错误类型的测点坐标改正方法及其注意事项,并用VC编写了相应的程序工具,经实验数据验证了它的可行性和正确性。该方法的提出和应用,可提高外业测绘工作的效率,具有较高的实际应用价值。     

一种适用大旋转角的GPS网三维平差方法

在工程测量中往往采用工程坐标系,该坐标系坐标轴可能与GPS采用的WGS84坐标系的相应坐标轴间存在较大的旋转角,此时若仍直接按照一般方法进行三维约束平差计算会给结果带来不利影响,本文给出了一种适用大旋转角的GPS网三维平差方法,该方法能够很好地处理大旋转角时直接采用一般三维平差模型计算带来的不利影响,同时又能够获得平差后工程网中各点的点位精度。工程应用表明该方法非常有效,具有很好的应用价值。     

基于TGO软件的GPS网同步环及异步环提取

美国Trimble Geomatics Office(TGO)GPS数据处理软件被测绘工作者广泛使用,但因其对环闭合差的检核是用水平分量和垂直分量表达,不能按我国GPS规范,分别对同步环及异步环以三维坐标分量方式检验环闭合差,而给使用带来极大不便。本文提出利用TGO的环闭合差报告和数据交换文件中的有关信息解决此难题,用VB编写成TGO辅助程序加以实现,并与不同的软件进行比较分析,说明该程序可以应用于工程实践中。     

GPS卫星定轨研究及STK仿真分析

首先对GPS卫星的轨道定轨的原理进行了简单描述,以卫星的广播星历数据为基础,计算出卫星的16个轨道参数,进而得到该卫星任一时刻的瞬时坐标。以2017年4月7日的GPS07号卫星的广播星历数据为例,计算该GPS卫星当天的轨道坐标,并将结果与当天IGS提供的精密星历所提供的卫星轨道坐标进行比较,计算结果显示广播星历误差可达5 m。最后使用STK软件调用MATLAB软件读取数据进行仿真分析,模拟出卫星的轨道,并计算出卫星的坐标,数值结果可为轨道设计提供技术参考。     

GPS在机载雷达探测精度评估中的应用

介绍了WGS-84坐标到机载雷达坐标的转换过程和计算公式,阐述了利用GPS定位数据及其精度。在计算载机与目标的距离精度的基础上,推导了有关的计算公式,并进行了实例计算。计算结果表明：计算公式推导正确,其测距和测角精度可以作为机载雷达的精度基准,来评估机载雷达的测距、测角精度。     

Accurate absolute GPS positioning through satellite clock error estimation

 An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at 30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns (3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes. For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than 40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption. Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating 30-s satellite clock errors and interpolating them. Received: 16 May 2000 / Accepted: 23 October 2000     

GPS接收机时钟控制方法

对多种GPS接收机长时间的静态观测数据,用单点定位算法,计算GPS接收机每一个历元的接收机坐标和钟差,分析计算钟差的变化规律,并了解在完成GPS接收机的定位和时钟的校准后,去如何控制其时钟。     

高精度GPS基线向量网平差

系统地论述了利用基线向量作为虚拟观测量进行平差的基本原理，着重对双因子抗差估计、系统参数求解、方差分量估计等在GPS基线网平差中的应用进行了分析，最后简单介绍了基线向量网平差软件GPSADJ。     

利用IRS-P5立体像对快速提取地震灾区震后DEM

针对地震灾区震后DEM数据获取困难的问题,总结出一种较传统方法更加快速便捷的实现途径。利用易测E640GPS接收机和MobileMapper手持接收机采集GPS卫星数据,并对GPS数据进行后差分处理得到控制点坐标,以这些控制点作为IRS-P5立体像对的地面控制点,并根据IRS-P5立体像对生成最终的DEM数据。本文使用这种方法成功获取了控制点并在Envi软件中使用IRS-P5立体像对生成DEM,并对DEM进行精度评价。     

高程拟合变换的平面坐标获取方法研究

提出一种基于高程拟合的数据处理方法,充分利用GPS高精度的三维观测,实现了将三维空间坐标转换为二维平面坐标.通过与传统椭球投影的结果对比,两者平均点位偏差为0.6 mm,结果表明了方法的正确性.由于无需椭球投影,这为平面坐标的数据处理提供了一种简单可行的方法.     

使用参照物的射电望远镜中心坐标测量方法

为满足新建射电望远镜在单站或多站联合进行的深空探测或射电天文观测对中心坐标精确测定的要求,提出一种利用已知精确中心坐标的望远镜作为参照物,测量地平式射电望远镜中心点坐标的方法和测量数据处理方法。这一方法对场地和设备的要求较低,能够得到毫米级或亚毫米级的位置精度。尤其适合对天线阵列的中心位置进行测量。对国家天文台密云观测站的40 m射电望远镜进行了中心坐标测量,位置均方根误差为2.312 mm,满足了后续的观测工作对其位置的需求。