初始种群范围及运行参数对遗传算法解算GPS病态方程的影响

通过实验研究了GPS快速定位病态方程中参数的搜索范围对基线及双差模糊度解算精度的影响,通过GPS基线解算实例研究了种群大小、交叉概率、变异概率及最大进化代数等参数设置对GPS基线及双差模糊度解算精度的影响。计算结果表明,如果测站近似坐标精度达到±0.5m以内,仅利用2个历元的单频载波相位观测数据,利用遗传算法可得到较准确的模糊度浮点解,有利于模糊度的快速固定。种群大小、交叉概率、变异概率及最大进化代数对遗传算法解算精度有一定的影响,通过实验将其分别设置为80,0.75,0.02,400,计算结果表明这些参数的设置是合适的。     

基于遗传算法的GPS病态方程的解算

为准确解算仅有少数几个历元的GPS载波相位观测数据的病态定位方程,将GPS快速定位的病态法方程求解问题转化为一个函数优化问题,应用遗传算法求解病态方程,避免了法方程的求逆运算,从而可以得到参数的近似最优解。实验表明,通过设计合适的适应度函数、确定合理的初始种群范围并选择合适的遗传算法运行参数,可使GPS快速定位病态方程参数浮点解的精度得到大大提高,接近参数正确值,有利于快速固定模糊度。该成果对于缩短GPS定位时间、提高GPS定位精度具有一定的意义。     

改进LAMBDA算法实现GPS整周模糊度快速解算

针对LAMBDA算法在实时解算GPS整周模糊度过程中存在模糊度浮点解偏差大、搜索范围大的缺点,采用Tikhonov正则化改进LAMBDA算法,对宽巷双差观测方程和L1双差观测方程中未知参数的系数矩阵进行奇异值(USV)分解,用分解后的协方差矩阵替换经典LAMBDA算法的协方差矩阵进行整周模糊度的搜索,该算法提高了模糊度浮点解的精度,缩小了模糊度的搜索范围.为了验证本文算法的正确性,对实测GPS基线观测数据进行了实验分析.结果表明:改进后的LAMBDA算法模糊度浮点解精度显著提高,改进后的LAMBDA算法模糊度固定成功率可以达到100%,可以无需初始化时间即可固定模糊度整数解,快速实现厘米级定位.     

基于粒子滤波的GPS定位解算方法

针对GPS定位解算将非线性GPS伪距方程线性展开,产生较大定位解算误差的问题,采用粒子滤波算法定位解算伪距方程。实验结果表明,基于粒子滤波的GPS定位解算优于卡尔曼滤波,有效提高了GPS导航定位的精度和可靠性。     

基于天牛须种群算法的整周模糊度解算算法

如何快速、准确的固定整周模糊度是载波相位测量中的一个关键问题。为了提高整周模糊度搜索速率,本文提出了一种基于天牛须种群算法(Beetle Antennae Colony Search, BACS)的整周模糊度解算算法。通过与BAS算法、BAS-Nadam算法、LAMBDA算法以及MLAMBDA算法进行解算速率、稳定性的对比实验,在三维模糊度解算时,BACS算法在与LAMBDA和MLAMBDA算法解算成功率相当的情况下,能利用更少的时间搜索到模糊度最优解。为了验证BACS算法在高维模糊度解算以及工程解算情况下是否适用,进行了高维模糊度解算的实验以及单频单GPS系统下BACS算法的应用实验。分析及实验表明,BACS算法能很好保证高维模糊度解算的实时性和鲁棒性,对于12维模糊度解算,平均解算时间0.068秒,解算成功率为92%,对于低维模糊度解算,解算速率更快,解算成功率更高。在单频单GPS系统工程解算中,x,y,z方向定位精度分别为±0.008米,±0.01米,±0.01米,能达到厘米级精度定位。     

GNSS整周模糊度概率特性

为了描述GNSS定位结果的可靠性和整周模糊度的概率分布,采用理论分析和实验的方法,推导了各种整周模糊度取整方法的成功率,分析了针对现代化后的GPS和Galileo系统的TCAR/MCAR方法。实验验证了LAMBDA算法能够较大提高模糊度取整成功率。研究结果表明,LAMBDA算法是一种比较理想的模糊度解算方法,TCAR/MCAR是LAMBDA算法在多频情况下的特例。研究结论有助于提高GNSS载波相位定位的可靠性。     

GPS接收机对移动载体姿态测量方法的研究

本文主要论述了使用三个GPS接收机通过载波相位测量,对运动目标进行姿态测量的一种解算方法,同时介绍了模糊度的快速解算和多路径效应的削弱方法。     

利用分块迭代法解算GPS整周模糊度

为实现GPS动态实时相位差分中整周模糊度参数快速精确解算,本文从参数估计的角度出发,针对常规方法的不足引入分块选代法,介绍其原理,将分块迭代法应用于GPS动态定位整周模糊度的解算,并对结果进行比较和分析,得出一些有益结论。     

GPS相位模糊度固定对钟差解算的影响研究

分析了全球定位系统(GPS)载波相位模糊度固定对接收机钟差解算的影响,并利用GRACE-FO实测数据基于不固定模糊度、固定单差模糊度和固定双差模糊度三种方法解算了三组钟差,最后通过与官方产品比较和重叠弧段比较两种方法进行了质量评估.结果显示：固定单差模糊度和固定双差模糊度所解算的相对钟差与官方产品差异的标准差(17.2和13.2 ps)比不固定模糊度(32.8 ps)分别减小了48%和60%;重叠弧段差异标准差(2.3和0.7 ps)比不固定模糊度(11.4 ps)分别减小了80%和94%,比官方产品(3.6 ps)分别减小了36%和81%.以上结果表明固定GPS相位模糊度可显著改善相对钟差精度.     

多约束条件的全球定位系统单频单历元短基线定向技术与实现

通过研究全球定位系统(GPS)伪距测量精度对GPS载波相位差分技术在短基线定向问题中的影响,提出利用基线长度、基线俯仰、卫星之间几何关系的多约束最小二乘整周模糊度实时搜索算法,给出单频单历元进行短基线定向的具体过程和需要注意的关键问题.算法采用单历元解算,规避载波相位周跳问题,极大地减小初始化时间.静态和动态实验结果均表明:该方法快速有效,解算成功率高,具有较高的定向精度.     

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.     

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。     

单频GPS载波相位整周模糊度解算研究

介绍了一种求解单频GPS载波相位整周模糊度的改进算法.通过Tikhonov正则化,减弱GPS快速定位中少数历元情形下法矩阵的病态性,得到更接近整周模糊度准确值的浮点解.然后对整周模糊度的方差协方差阵白化滤波,减弱短时间内双差整周模糊度之间的相关性,取整后得到整周模糊度的固定解.并结合一个实例与白化滤波、Lambda方法和白化滤波 Lambda方法进行对比,验证改进方法的效果.     

附加约束法在单频GPS快速静态定位中的应用

针对在短时间内GPS观测方程的法方程容易形成病态的实际,探讨用附加约束条件来消除其病态性的方法,然后用LAMBDA方法确定其整周模糊度,实验证明,对于单频GPS接收机,利用5个历元数据,使用该技术即可正确确定整周模糊度,从而实现厘米级定位.     

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...     

基于改进的遗传算法解算GPS双差模糊度的研究

将遗传算法(GA)应用于GPS双差模糊度解算过程,针对双差模糊度的整数特性,进行了实数编码的改进、遗传算法的改进等算法设计,实现了双差模糊度直接在大范围、高精度、整数域上的优化搜索,提高了解算的稳定性与高效性。试验结果表明,经过改进的实数编码GA可以取得比二进制编码GA更高的效率和成功率,更适于双差模糊度搜索。     

Near-field surface displacement and permanent deformation induced by the Alaska Mw 7.5 earthquake determined by high-rate real-time ambiguity-fixed PPP solutions

High-rate GPS data from the United States continuously operating reference stations in the Alaska region are processed using the recently developed precise point positioning （PPP） technique. The traditional PPP technique does not fix ambiguities into their integers because these ambiguities do not have an integer nature when data from a single receiver, as well as precise orbit and clock corrections, are used. Additional corrections, i.e., uncalibrated phase delay （UPD）, are needed to fix integer ambiguities and consequently improve positioning accuracy. This study proposes a methodology to compute for wide-lane and L2 （the second L-band frequency） UPDs using the geometry-based model and subsequently applies these parameters to the computation for ambiguity-fixed solutions. The instantaneous displacements of near-field sites, as well as the permanent deformations after the earthquake, are therefore obtained for the January 5, 2013, Alaska earthquake. The real-time performance of PPP solutions are assessed by considering realistic data latency and data interval of corrections. Ambiguity-fixed solutions are compared with ambiguity-float ones. The comparison shows that the positioning accuracy can be improved significantly when the ambiguities are fixed correctly. The solutions using the real-time corrections are also compared with those using post-processing corrections, i.e., Center for Orbit Determination in Europe final orbit and clock. Although the accuracy is somehow degraded because of the data latency and data interval, the real-time results are satisfactory for use in monitoring the small-scale deformation （1-2 cm） caused by the Alaska earthquake. In addition, the kinematic ambiguity-fixed PPP solutions for 7 days around the earthquake are calculated to obtain permanent pre- and post-earthquake deformations. The deformations computed from real-time and post-processing corrections do not appear to be significantly different.     

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.     

基于基线约束及递推多历元的改进GNSS定姿技术

在GNSS单频姿态测量技术中,利用单差载波相位和码相位结合模型以及CLAMBDA算法(带有基线约束的最小二乘降相关平差算法)解算整周模糊度可以达到较好的定姿结果,但解算成功率不高。针对这一问题,提出了一种多基线三角形约束的递推多历元方法。三角形基线约束主要针对副基线,利用它可以使CLAMBDA算法得出的整周模糊度更准确。而递推多历元则保证了在此时刻没有解出整周模糊度时仍然可以计算出姿态角,主、副基线都适用。2种方法结合,进一步提高了姿态解算的成功率。对副基线的解算进行了验证,实验证明,这种方法将副基线的成功率提高到99.7%以上。