Research on the estimation of GPS phase ambiguities by triple frequency observations

As a part of modernization of GPS, a new signal with a frequency of 1 176.45 MHz will be made available to the civilian community and can provide more measurements for positioning in combination with the well known L1 and L2 signals. Applying the law of variance-covariance propagation, the correlation of triple-frequency ambiguity is discussed, the L1 ambiguity is week correlate with wide lane and long wide lane ambiguity. Under a comprehensive analysis of linear combination, no matter how long the baseline is, the ambiguities of long wide lane carrier phase combination can be determined using code measurements directly, ambiguity of short baseline can be fixed fast because of very small standard error of ambiguities of many linear combinations, the main efforts of TCAR are ambiguity resolution of long baseline. The ionosphere-free combinations used widely are not suitable for ambiguity resolution because of very short wavelength with high noise and very large standard error of ambiguity. The smoothing procedure reduces the standard errors of code and also can improve ambiguity estimation, the ambiguity of wide-lane, in long baseline case, can be rounded to the nearest integer within six epochs.     

适用于航天器的GPS姿态测量算法和软件设计

为发展小卫星 ,需要研制成本低、小而轻又能满足精度的姿态测量系统。论述了利用全球定位系统 ( GPS)载波相位观测值进行姿态测量的原理 ,介绍了航天器姿态测量软件 THADS的算法和软件设计。在软件设计时 ,采用了周跳和粗差判定的改进方法 ,编制了相应的模块 ,结合地面实验数据进行仿真计算 ,在 1m左右的基线上姿态均方差小于0 .4°。结果表明利用 GPS载波相位进行航天器姿态测量具有良好的应用前景     

移动定位与GPS定位相结合的实时车辆定位系统研究

介绍了一种基于移动定位与GPS定位相结合的实时车辆定位系统，并详细描述了系统实现的关键部分。通过获取和分析车辆地理位置数据以及基于GSM网的无线网络传输，实现了移动车辆的实时定位。     

GPS单频单历元定姿算法性能分析与改进方法

为了提高LAMBDA在单频单历元情况下的性能和成功率,对该定姿算法的性能进行了理论研究,分析了影响搜索效率的因素,并提出了一种新的求解模型.将未知的整周模糊度拟合成噪声,能够显著提高搜索效率,同时利用模糊度存在范围等约束条件对原算法的成功率进行了改善.实验表明:相比于原算法,改进算法能够有效减少GPS姿态解算的时间,同...     

基于国家测绘局GPS连续运行参考站的定轨

为了解决采用地面GPS连续运行参考站进行高精度定轨问题,采用轨道积分方法,利用国家测绘局8个GPS连续运行参考站和9个中国周边IGS连续运行参考站,设计了多种天数的区域性定轨计算方案,研究了轨道确定的理论、步骤和参数设置规律.结果表明:3天轨道解的平均精度为0.19 m,5天轨道解的平均精度为O.21 m,7天轨道解的平均精度为O.28 m,3天解平均定轨精度最高,优于0.2 m,证明了并非随着地面数据天数的增加而精度随之增加,可以用最少的数据量获得最优的定轨结果.定轨试验计算的是区域性轨道,与全球轨道相比,存在一定的偏差.该成果对我国定轨研究特别是未来的广域增强系统轨道预测具有一定的指导意义和参考价值.     

GPS相对定位的数学模型及测量线性组合的相关性研究

分析了GPS变形监测网基线处理中的系统误差,在此基础上给出GPS的相对定位与绝对定位、实时与非实时定位、静态定位与动态定位的数学模型构建方法和数学模型,并对其观测量线性组合的相关性进行了研究,给出确定权阵的方法,最后导出了常用的坐标转换公式。     

优化GPS测量软件系统的研制及其在岩土工程监测中的应用

为了提高GPS在岩土工程中的应用水平,研制了集GPS电子测量规范、适合多类型GPS接收机外业记录的电子手簿、岩土工程监测任务模拟软件和结果分析软件及岩土工程GPS监测网的优化设计于一体的面向岩土工程监测的GPS测量软件系统,并讨论了GPS网的基线重复性检核、同步环检核、异步环检核、坐标转换、网平差、GPS监测网的优化设计和形变量的显著性检验等关键问题.最后,通过对辽宁省抚顺地区的某矿区进行边坡变形监测的研究,验证了该软件系统不仅具有良好的实用性和可靠性,而且可以达到毫米级的监测精度,完全能够满足岩土工程监测的要求.图4,表3,参12.     

Precise orbit determination for GRACE with zero-difference kinematic method

Thanks to the high performance of the spaceborne GPS receiver and the availability of precise IGS orbit and clock products, ze-ro-difference kinematic precise orbit determination (POD) has been turned out to be a new effective method in orbit determination for the LEO satellites. Zero-difference kinematic POD, which is based on the GPS measurements only from the spaceborne GPS receiver, does not depend on the force models and orbit design. From this point of view, kinematic POD is suitable for the Earth observation satellites at very low altitudes, such as CHAMP, GRACE and GOCE, etc. This paper first reviews the basic ze-ro-difference GPS observation model. Then a modified data quality control scheme is put forward. Finally, a block-wise least squares algorithm, which first separates the parameters into several groups and then solves the parameters by elimination and back-substitution, is discussed and proposed for the kinematic orbit determination. With the above algorithms, we developed kinematic POD software to solve the orbit suitable for one-week GRACE observations. Comparisons with the published Rapid Science Orbit (RSO) indicate that, using our approach to determine the orbit, the accuracy in the radial direction can achieve 3―4 cm for GRACE-A, and 3―5 cm for GRACE-B.     

Precision ERS-2 orbit determination combining multiple tracking techniques

Both of the oceanographic research by using altimetry and the application of InSAR of ERS-2 satellite need the precise ephemerides of the satellite. In this note, the ERS-2 orbit is precisely determined by using SLR and PRARE observations to take advantage of the high accuracy of SLR and the widespread data coverage of PRARE. Based on the software system SODS-VCE established by us, the ERS-2 orbits in 1997 are calculated. The evaluation from tracking data fits, endpoint consistency of orbital arcs and comparison with independent orbit implies an orbit accuracy of 5–6 cm in radial component which can satisfy the requirement of being better than 10 cm in oceanographic research by altimetry, being less than 20 cm in cross-track component which can meet the requirement of InSAR. In orbit computation, the method of variance component estimation is employed to weight the SLR, PRARE range and Doppler measurements properly. The results indicate that the application of the method can improve the computation accuracy efficiently.     

数据融合在搜索结果多元化上的应用

信息检索系统不仅需要考虑文档的相关性,还要考虑文档的多样性和新颖性。针对信息检索结果的多元化问题,探讨了数据融合方法在搜索结果多元化上的适用性。针对线性组合方法,重新考察了成员系统的权重分配策略。通过考虑成员检索系统的有效性和成员检索系统之间的差异性,提出了一种比较简单方便的基于集合覆盖率的方法,使得采用这种权重分配方式的线性组合方法在结果的多样性上能够有所改善。实验采用了3组来自于TREC文本检索会议的针对Web检索多样化任务的数据,实验结果表明在多样性方面,所提出的数据融合方法均能提高检索结果的性能,优于最佳的成员检索系统。     

GPS机动车辆定位监控系统开发研究

应用GPS全球卫星定位技术、GSM全球数字移动通信技术、GIS地理信息技术和计算机网络技术开发机动车辆定位监控系统的研究 .     

阻尼白化滤波及其在GPS模糊度快速解算中应用

针对矿区开采沉陷观测中存在的两次观测的变形值不大等特点,将其作为约束条件,结合改进的白化滤波算法,提出了一种适合单频GPS监测开采沉陷的阻尼白化滤波快速解算模糊度算法。针对一般白化滤波方法对白化处理后模糊度直接取整的做法,提出在假设检验通不过时,引入LAMBDA中的条件最小二乘方法进行搜索,可以有效提高模糊度解算成功率。这个算法为用GPS监测矿区开采沉陷、大坝、滑坡、大桥及高层建筑物等的变形时的模糊度解算提供一条有效途径。     

An improved regularization method to resolve integer ambiguity in rapid positioning using single frequency GPS receivers

A new approach is employed in GPS rapid positioning using several-epoch single frequency phase data.Firstly, the structure characteristic of the normal matrix in GPS rapid positioning is analyzed. Then, in the light of the characteristic, based on TIKHONOV regularization theorem,a new regularizer is designed to mitigate the ill-condition of the normal matrix. The accurate float ambiguity solutions and their MSEM (Mean Squared Error Matrix) are obtained using several-epoch single frequency phase data. Combined with LAMBDA method, the new approach was used to fix the integer ambiguities correctly and quickly using MSEM instead of the cofactor matrix of the ambiguities. Finally, a baseline over 3 km is taken as an example. The fixed integer ambiguities by the new approach using five epoch single frequency phase data are the same as those fixed by Bernese software using long time data. The success rate of fixing the integer ambiguities is 100 percent using 197 group data.Compared with the traditional methods, the new approach provides better accuracy and efficiency in GPS rapid positioning. So, the new approach has an extensive application outlook in deformation monitoring, pseudokinematic relative positioning, and attitude determination, etc.     

基于信噪比的正则化方法及其在GPS快速定位中的应用

本文针对GPS快速定位中设计阵病态性的特点,提出了一种新的正则化方法.该方法首先利用参数LS估计的信噪比提取了各个参数是否受到复共线性严重危害的信息,从而在一定程度上揭示了设计阵复共线性结构的特征.然后针对复共线性的特征,以信噪比为依据构造正则化矩阵,以极小化均方误差为目标选取正则化参数,提出了基于信噪比的正则化方法（SNR）.最后进行的数值试验表明,本文提出的SNR方法较好地利用了复共线性特征的信息,处理病态问题针对性更强,解算效果更佳.     

英语中常见的歧义现象及消除方法

从语言三要素的角度归纳了英语中常见歧义现象的类型； 分析了导致歧义现象的种种因素及诸因素对语言交际的影响， 从而找出辨识及消除歧义的基本方法， 以达到在英语语言交际中准确地表达思想、传递信息     

Precise GPS/GNSS positioning solution for airborne data acquisition systems

The precise positioning of aircrafts during flights belongs to the great challenges with respect to the development of airborne data acquisition systems. Satellite positioning systems like GPS offers a unique capability for precise positioning but requires in depth knowledge of GPS in airborne applications, e.g.GPS for high dynamic application, integration of GPS with other sensors, dynamic behaviour of aircrafts or antenna location. For its positioning reference system of Flight Inspection systems Aerodata AG has developed a robust GPS carrier phase ambiguity solution P-DGPS, Precise Differential GPS combined with complementary sensors like INS, barometers, radio altimeters or laser altimeters as well as laser trackers. Using recorded data during the flight the algorithm offers also the capability to calculate more accurate positions in post-processing. The presented sensor fusion algorithm using GPS without differential corrections (SGPS, standalone GPS) offers a precise height reference solution for approach calibration based only on aircraft-based sensors. SGPS data are combined in post-processing with inertial, pressure, radio and laser altimeter data. Flight trials with a Bombardier "Global Express" at Braunschweig Airport on May 2002 shows the achieved accuracies of the height reference solution calculated by SGPS in comparison to P-DGPS. The SGPS solution for precise height calculation of special mission aircrafts provides accuracies in the order of 5 m and at the runway's threshold in the order of 30 cm.     

Drazin逆的线性组合及其应用

借助于矩阵的Schur三角化过程,给出矩阵的Drazin逆表达形式,进一步给出了矩阵线性组合的Drazin逆表示形式,推广了Robert的结论.     

Precise orbit determination for Jason-1 satellite using on-board GPS data with cm-level accuracy

The joint US/French Jason-1 satellite altimeter mission, launched from the Vandenberg Air Force Base on December 7, 2001, continues the time series of centimeter-level ocean topography observations as the follow-on to the highly successful T/P radar altimeter satellite. Orbit error especially the radial orbit error is a major component in the overall budget of all altimeter satellite missions, in order to continue the T/P standard of observations. Jason-1 has a radial orbit error budget requirement of 2.5 cm. In this work, two cycles (December 19, 2002 to January 7, 2003) of the Jason-1 on-board GPS data were processed using the zero-difference (ZD) dynamic precise orbit determination (POD) technique. The resulting Jason-1 orbit accuracy was assessed by comparison with the precise orbit ephemeris (POE) produced by JPL, orbit overlaps and SLR residuals. These evaluations indicate that the RMS radial accuracy is in the range of 1－2 cm.     

软件可靠性测试充分性的多准则判定及应用

在分析软件可靠性测试充分性特点的基础上,提出一种多准则充分性判定方法.依据运行剖面构造系统的使用模型,通过假设检验和贝叶斯推断确定测试用例数量,建立差异函数判断测试模型与使用模型的偏离,根据软件失效情况进行多轮次充分性判定,并使用贝叶斯方法积累测试信息,同时利用测试结果开展软件可靠性的评价与预测.实例分析表明,多准则充分性判定方法对可靠性测试用例集要求更加严格,使得根据该测试用例集的测试结果开展可靠性评价与预测更具可信性.     

VRS系统流动端单历元整周模糊度搜索

为了实现VRS系统虚拟参考站和流动端单历元模糊度快速搜索,采用宽巷相位和C码伪距观测值组成联合双差观测方程,用改进LAMBDA方法搜索宽巷载波双差模糊度,并提出双频相位观测值组合模型逐星固定L1和L2双差模糊度,研究结果表明:该方法具有很高成功率和效率,单历元定位精度优于3 cm,该研究实现流动端单历元实时高精度动态定位。