卫星信号发射时刻的无偏恢复

卫星信号发射时刻在导航定位中是一个重要的参数,但是在城市峡谷等弱信号条件下,接收机可能完成不了所有卫星信号发射时刻的组装。在伪距定位中卫星信号发射时刻的组装和粗时段导航中卫星信号发射时刻的恢复(有偏)技术基础上,提出一种无偏的卫星信号发射时刻恢复方法,前提是卫星至少能完成一颗星的伪距测量,并且具有150km误差范围内的先验位置和辅助星历。利用BDS B1和GPS L1中频数据在软件接收机平台进行了BDS,GPS信号发射时刻无偏恢复验证实验证明了方法的有效性。     

基于短基线的北斗动动定位方法的几点探讨

针对北斗动动定位中接收机信号易受遮挡导致无法实时准确进行相对基线测量的问题,本文提出了一种利用惯性测量信息辅助动态模糊度的解算方法。通过载波相位差分观测方程与惯导观测方程组合的方式,讨论在共视卫星数目在不同观测条件下的模糊度求解方法。在此基础上,建立了基于惯导信息辅助的动动定位组合试验系统,利用车载试验进行了相关测试。结果表明,在可视卫星数目较少的情况下,BDS定位精度效果优于GPS;利用IMU信息辅助提高了定位连续性和精度。     

基于GT的钟差预测模型辅助GPS定位算法研究

为了解决在强干扰环境下由于GPS卫星信号被遮挡而无法定位的问题,从灰色理论(GT)的角度探讨了接收机的钟差序列,提出一种利用灰色理论的钟差预测模型辅助GPS定位的方法。对预测模型的基本思想和具体实现步骤作了详细的介绍,并且将钟差预测值引入到GPS接收机中,实现信号遮挡情况下GPS接收机的定位解算。通过对实测数据的验证分析表明,该钟差预测模型对钟差序列有很好的预测效果,能够在仅有3颗可观测卫星的情况下实现接收机的定位解算。     

改进的遗传算法在GPS基线解算上的研究

遗传算法(GA)处理数值优化计算问题具有的简单通用、并行、稳健等特点,因此应用于高精度GPS定位的基线解算过程。针对双差模糊度的整数域和基线向量的实数域解的特性,进行了GA算法改进,包括实数编码的改进、遗传算子及其控制参数等算法设计,提出了基于非线性最小二乘准则的GPS相对定位同步解算基线向量和双差模糊度的优化搜索新方法,避免了分步解算模糊度中对浮点解的依赖性,首次实现了大范围、高精度、整数实数不同域上的同步求解,提高了GPS相对定位的稳定性,也体现了遗传算法的优越性。算例表明改进的实数编码遗传算法对同步解算GPS相对定位是可行有效的。     

利用DUFCOM和DC算法的GPS单历元双差整周模糊度快速确定算法

为解决DUFCOM方法单历元解算GPS双差整周模糊度因观测卫星数多导致解算效率低而影响GPS高频数据实时动态解算这一问题,同时考虑到DC算法解算效率高的优点,对观测卫星进行筛选分级处理,提出了一种快速确定算法。算例表明,该算法可避免在应用DUFCOM方法中二级卫星对一级卫星双差整周模糊度解算效率的影响,使得GPS单历元确定双差整周模糊度的效率显著提高,达到了GPS高频数据实时动态解算的目的。     

基于部分模糊度解算的BDS/GPS组合RTK算法

GNSS多频率组合RTK定位逐步进入实际应用,存在模糊度维数增多、搜索空间增大,导致模糊度搜索运算量增大及模糊度固定效率低等问题。文中提出一种多星座部分模糊度解算算法,该算法综合考虑卫星高度角、模糊度固定成功率及Ratio值来筛选卫星进行模糊度解算。通过一组动态跑车实验分析表明:相比于全模糊度解算(FAR),部分模糊度解算(PAR)可以有效地提高BDS/GPS组合RTK的模糊度固定率,其模糊度固定率从79.9%(FAR)提高到99.1%(PAR),且PAR算法定位结果可靠性更高。     

基于遗传算法的高精度GPS相对定位解算研究

在高精度GPS相对定位中,初始模糊度的确定是保证高精度、快速定位的关键。依据遗传算法(GA)的稳健、并行和简单通用等特点,基于遗传算法的相对定位解算问题具有现实意义。基于改进的遗传编码和算法,建立同步实现相对定位坐标向量和模糊度的解算模型和流程,并通过实测数据的算例,对所提出算法的可靠性、搜索效率进行论证。     

基于BDS+GPS中长基线多频RTK定位的快速收敛模型

随着全球卫星导航系统(GNSS)进入多系统时代,天空中导航卫星的可见数不断增加,而我国北斗卫星导航系统(BDS)也已开始面向用户提供三频导航信号,这都有利于改善RTK定位的精度和可靠性。本文提出了一种BDS+GPS中长基线多频RTK定位算法,先以较高成功率快速固定BDS的两个超宽巷模糊度,继而通过简单变换得到BDS宽巷模糊度,然后用其辅助提高GPS宽巷模糊度固定成功率,最后采用将电离层延迟误差和对流层延迟误差参数化的策略以加快窄巷模糊度浮点解的收敛速度,缩短模糊度首次固定的时间。结合实测数据进行的验证分析结果表明,利用本文算法对模糊度进行解算是可行的。     

基于测元融合的GPS与北斗二代定位算法研究

针对GPS和北斗二代的测量原始数据,研究了卫星导航定位问题,给出了一种基于测元融合的定位算法。通过对卫星信号模拟器数据的融合解算,得出了目标的定位结果,并与模拟器真值数据做比较分析。结果表明:融合算法正确有效,该方法可以在测量的相关领域中应用。     

BDS/GPS单历元短基线动对动定位性能分析

针对在城市峡谷环境下观测卫星较少、观测质量差和周跳频繁,导致动对动定位过程中双差模糊度不连续的问题,提出了一种GPS/BDS组合系统的单历元模糊度解算方法。通过GPS/BDS组合定位提高了卫星的可用数量,利用单历元模糊度固定减弱了周跳频繁带来的影响。实验采用GPS/BDS组合的7组数据,分析了在不同高度角下动对动定位单历元解的模糊度固定率、解算失败率、粗差率和定位精度。结果表明,GPS/BDS组合动对动定位单历元模糊度解算方法,在高遮挡的城市峡谷环境仍然可以取得较好的定位结果。     

多传感器与道路网数据用于汽车导航的研究

对车载导航系统中GPS接收机，车论计数器和电子罗盘传感器数据与导航电子地图所提供的道路网络数据进行了综合处理，建立了道路网络数据的网络拓扑关系，在此基础上提出了基于道路网络拓扑关系，利用GPS接收机，车轮计数器和电子罗盘传感器对汽车进行实时定位的算法。最后，对导航中汽车的定位误差进行了分析。实验证明，GPS接收机，车轮计数器和电子罗盘传感器与道路网络数据综合，在导航过程中能够补偿GPS信号技失，实时、高精度、高可靠性地确定汽车的位置。     

A new coarse-time GPS positioning algorithm using combined Doppler and code-phase measurements

A new coarse-time Global Positioning System (GPS) positioning algorithm based on the use of Doppler and code-phase measurements is proposed and described. The proposed method was demonstrated to be essential for reducing the time to first fix and the power consumption in a GPS receiver. Only 1 ms of data is required to obtain a positioning fix with accuracy comparable to that of the traditional GPS navigation algorithm. The algorithm is divided into two parts. In the first part, the Doppler measurement of the GPS signal is used to determine the coarse user position. With proper constraints, the required time accuracy for the Doppler measurements can be relaxed to be as long as 12 h. In the second part of the algorithm, the accurate user position is calculated by means of the 1 ms code-phase data. The traditional tracking process is no longer necessary in the proposed algorithm. Using the acquired 1-ms code-phase measurement, the positioning accuracy was determined to be approximately a few tens of meters in our experimental results. However, if the data length is extended to 10 ms, the positioning accuracy can be improved to within 10–20 m, which is similar to that of the traditional GPS positioning method. Various experiments were conducted to verify the usefulness of the proposed algorithm.     

一种基于多普勒频移的GPS自适应滤波算法研究

针对接收机的动态模型对GPS定位精度的影响,提出了一种基于多普勒频移观测的高动态GPS自适应滤波算法。该算法利用GPS伪距测量值以及利用信号载波的多普勒频移所获得的伪距率测量值,在GPS动态滤波中同时观测伪距和伪距率。借助于移动目标的运动矢量模型以及GPS定位误差模型建立了滤波方程。重点讨论了运用该模型进行Kalman滤波的实现过程。仿真实验表明,该模型与传统的方差自适应模型相比,位置精度提高了32%、速度精度提高了25%,应用本文算法能够提高定位精度和改善接收机的动态性能,拓宽高精度、高动态导航的应用范围。     

接收机五参数定位算法研究

介绍了卫星钟差数据仿真方法以及基于星间双向测距的导航卫星两步滤波时间同步算法。仿真数据结果表明,与一步滤波方法相比,两步解算方法的时间同步精度有一定提高。     

基于卡尔曼滤波的GPS静态定位精度分析

GPS静态定位精度是实现精密测量的关键。简要介绍了GPS静态定位原理和卡尔曼滤波技术,针对GPS信号噪声特点,建立GPS静态定位数据处理的数学模型,设计卡尔曼滤波算法,通过对三种定位方式的实测数据进行比较分析,得出相关结论,为工程应用提供有益的参考。     

Identification of GPS positioning solutions deteriorated by signal degradations using a fuzzy inference system

The accuracy of GPS positioning based on pseudorange measurements under signal degradation environments is limited by poor satellite geometry and signal distortions due to diffraction and multipath. As a result, the GPS position solutions could become unreliable. Those deteriorated solutions should be identified and not used for navigation. For that purpose, methods for reliable identification of deteriorated GPS positioning solutions from a navigation receiver should be developed. In this paper, a fuzzy inference system is proposed to classify the quality of GPS positioning solutions. The input for the system includes the signal quality evaluated by the difference between the measured and expected carrier-to-noise density ratio (C/N0) and the satellites geometry strength evaluated by the dilution of precision (DOP) number. The proposed fuzzy inference system is developed based on the human knowledge and understanding of the problem under consideration and is further optimized using data acquired from the field. The test results indicate that the proposed method can be used for reliable identification of deteriorated GPS position solutions affected by signal degradations.     

Performance analysis of integrated GPS/GLONASS carrier phase-based positioning

Due to the different signal frequencies for the GLONASS satellites, the commonly-used double-differencing procedure for carrier phase data processing can not be implemented in its straightforward form, as in the case of GPS. In this paper a novel data processing strategy, involving a three-step procedure, for integrated GPS/GLONASS positioning is proposed. The first is pseudo-range-based positioning, that uses double-differenced (DD) GPS pseudo-range and single-differenced (SD) GLONASS pseudo-range measurements to derive the initial position and receiver clock bias. The second is forming DD measurements (expressed in cycles) in order to estimate the ambiguities, by using the receiver clock bias estimated in the above step. The third is to form DD measurements (expressed in metric units) with the unknown SD integer ambiguity for the GLONASS reference satellite as the only parameter (which is constant before a cycle slip occurs for this satellite). A real-time stochastic model estimated by residual series over previous epochs is proposed for integrated GPS/GLONASS carrier phase and pseudo-range data processing. Other associated issues, such as cycle slip detection, validation criteria and adaptive procedure(s) for ambiguity resolution, is also discussed. The performance of this data processing strategy will be demonstrated through case study examples of rapid static positioning and kinematic positioning. From four experiments carried out to date, the results indicate that rapid static positioning requires 1 minute of single frequency GPS/GLONASS data for 100% positioning success rate. The single epoch positioning solution for kinematic positioning can achieve 94.6% success rate over short baselines (<6 km).     

PERFORMANCE ANALYSIS OF INTEGRATED GPS/GLONASS CARRIER PHASE-BASED POSITIONING

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An enhanced bit-wise parallel algorithm for real-time GPS software receiver

Software-based global positioning system (GPS) receivers perform all the baseband signal processing and the high level functions on a general purpose processor. The heavy computational loads of the signal correlation in baseband processing make it difficult for software receivers to operate in real time. In order to improve the real-time performance, an enhanced bit-wise parallel algorithm has been developed in this study. The enhanced algorithm has been implemented and tested in a 12 channels real-time GPS software receiver. The system consists of a radio frequency front end, a data acquisition board and software that runs on a laptop with a Pentium-M 1.5 GHz processor running the Window^® XP operating system. The data acquisition board packs the 2-bit intermediate frequency samples with a 2-bit in/8-bit out shift register and transfers the packed samples to laptop through a USB port. The software running on the laptop performs all the baseband and navigation processing in real time. The test results show that the enhanced algorithm significantly improves the real-time performance of the software receiver by reducing the computational operations for signal correlation by 50% compared with the existing bit-wise parallel algorithm. Furthermore, the enhanced algorithm also reduces the amount of required memory for storing data for signal correlation.