关于坡面法向量求算的算法综述

通过对简单差分、二阶差分、Frame差分、三阶反距离权差分、三阶反距离平方权差分和三阶不带权差分6种常用坡面法向量算法的分析比较,得出在求算fx和fy时需要根据实际情况选择不同的差分算法以得到较好的结果。一般情况下三阶反距离平方权差分算法、三阶不带权差分和三阶反离权差分在计算精度上最佳。     

农用GPS接收机

天宝导航定位技术有限公司新近推出一款名叫Ag GPS 332型最优精选农用接收机。这种接收机可跟踪来自差分GPS信号源L1及L2 C／A码和载波相位信号，包括WAAS、EGNOS、信标和OmniSTAR信号。用户可选用两种天线，这两种天线可根据所接收到的信号提供不同的精度。据报道，组合式L1／L2天线可为RTK提供小于1cm的精度，为OmniSTAR HP提供小于10cm的精度，对OmniSTARXP提供小于20cm的精度。对OmniSTAR VBS提供小于1m的精度。     

罗兰-C小型有源接收天线设计与仿真

针对罗兰-C无线电导航信号接收需求,研究一种高性能的罗兰-C小型有源接收天线,可以减小天线体积和安装难度,方便罗兰-C导航接收机的使用,具有较高的实用意义. 天线主体采用磁棒线圈天线接收长波频段罗兰-C信号,在天线内设计了包含放大电路、带通滤波电路、差分输出电路和供电电路在内的前端信号调理电路,从而增大信号灵敏度,提高信噪比;设计了一体化的天线结构,以便工程化应用. 通过仿真和实测结果表明:该天线在工作频带内,可以全向高效接收罗兰-C信号,而且对接收到的微弱罗兰-C信号进行放大并滤除带外噪声,信号强度和信噪比满足使用要求. 该天线具有体积小、灵敏度高、使用方便的特点,可应用于罗兰-C无线电导航,组合导航、附加二次相位时延计算等场景.      

基于北斗导航卫星的伪卫星技术在区域定位中的应用

借鉴差分 GPS导航定位的原理 ,阐述了在北斗导航卫星支持下的伪卫星技术 ,探讨了其定位原理、系统配置、技术设计、信号结构、天线安装和使用条件等。实现区域快速无源导航定位 ,需要至少四个伪卫星站提供的导航信号。伪卫星定位导航具有自主、隐蔽、经济等特性 ,在区域定位中应用前景良好。     

基于VRS的差分GPS算法研究

随着差分GPS技术的发展,其应用于工程测量也越来越及,但随着基线长度的增加,常规差分GPS定位精度亦随之降低。为此,本文研究了基于虚拟参考站(Virtual Reference Station,VRS)的差分GPS定位算法,它能有效克服常规差分GPS存在的缺陷,使移动测量用户可在较大空间范围内获得均匀、高精度和可靠的定位结果。     

高性能的GPS／GLONASS一体化天线

人们特别感兴趣使用GPS和GLONASS一体化系统来改善卫星定位数据的可用性、精度和可靠性，尤其在需要高精谎和高度一体化的某些民用领域。另一方面，一些高精度应用，如一体化检测系统或差分基准系统，它们需要采用具有多径抑制能力强，相位一致性高，同时又能实现半球覆盖，而且增益方向图平滑，轴比最小等特性的天线。本将介绍一种最近开发成功的天线系统，该系统可以满足GPS L1/L2和GLONASS L1/L2系统频段内的性能要求。天线单元制作在介质层加载的叠层微带结构上，该微带结构平镶在波纹状接地平面上。重点强调的最佳多径抑制性能已经被实现，而且在这里详加介绍。本也已包括并介绍一些特殊的技术，用以改善辐射方向图和AR电平。本还讨论了有关宽带AR、输入反射系数和天线增益特性的一些设计条件。     

基于站间单差相位绕转数据估计测站天线旋转速率的方法研究

相位绕转在GNSS定位中是一种误差源,但包含接收机天线旋转的有用信息。提出了一种基于站间单差相位绕转观测数据估计测站天线旋转速率的方法。首先由无几何距离观测值的变化判断天线旋转的开始与结束时间,然后利用单颗卫星站间差分的无几何距离观测值求出测站的天线旋转角度,以及单颗卫星的测站天线旋转速率,最后将所有卫星计算的测站天线旋转速率按照高度角加权平均得到最终的天线旋转速率。通过精心设计实验方案,经实测数据验证,该方法可以精确地估计测站天线的旋转速率,在本实验中,天线旋转平均速率估计精度约为0.5°/s。     

TDD GPS技术与应用

TDDGPS全称是tender—deployable differential GPS，即易配置的差分GPS，它是由美国海岸警卫指挥控制工程中心设计发明的。通过采用可临时安置的天线，TDDGPS可提供大约10海里范围的差分信号。并且通过12小时的接收和处理GPS信号，海上灯塔就可以利用GPS信号进行辅助导航。     

基于虚拟观测值的伪距差分方法研究

针对当前伪距差分服务观测值双差模式基准站坐标涉密不能在线传输与伪距改正数模式标准格式无法兼容北斗卫星导航系统（BDS）的问题,本文基于局域连续运行参考站（CORS）网数据,生成虚拟格网综合伪距改正数,并进一步生成虚拟伪距观测值,向用户实时播发虚拟观测值与站点坐标,用于用户差分定位．实验证明,虚拟格网伪距观测值差分可为用户提供平面亚米级、垂直优于1.5 m的定位服务．对实验数据进行分析,给出了格网差分最优配置方案．本文方法在解决上述两个问题的基础上由于服务端计算压力恒定,不受用户数限制,从算法上解决了大量用户并发接入服务的问题．      

基于BD930板卡的RTK测量系统研制

针对物探测量作业中经常会遇到密林、峡谷、窄沟等遮挡严重的不良环境,导致可视卫星数减少、卫星信号不稳定,进而造成定位结果精度下降、作业效率降低等问题。本文提出了使用多系统兼容的高灵敏度BD930板卡作为接收机主板,给出了板卡的控制方法。研制出了一款实时动态定位手簿软件,并且利用网络通信技术搭建了差分数据链,多次在实际物探测量作业环境下对整个测量系统的性能进行了测试。结果表明,该系统在一定程度上提高了RTK适应困难环境的能力,所搭建的差分数据链使测量作业更加便捷、高效,能够满足工程应用的需要。     

基于单个GPS/BDS信标台增强的实时精密单点定位

随着IGS实时服务的推广,实时轨道、钟差产品可用于实时PPP;然而,在一些通讯条件差的地方,如偏远山区和广袤的海洋,差分信号的播发与接收仍然是实时PPP的障碍。文中提出一种基于单个GPS/BDS信标台的实时PPP定位方法:基站采用广播星历和无电离层伪距、相位观测值,实时估计耦合轨道、钟误差;单向通讯的方式播发给用户端,减小通讯量,提高用户端的定位性能。经过分别距参考站约200km和300km的流动站进行验证,通过约10~12min收敛,GPS/BDS组合可得到水平优于20cm的定位精度。本案验证了采用广播星历进行实时PPP的可行性,为海洋和偏远地区提供一种高精度定位方法。     

Generation of differential GPS corrections along with performance of quality control

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Generation of differential GPS corrections along with performance of quality control

The DGPS technique can provide considerably better relative positioning accuracy than the stand-alone GPS positioning, but the improvement depends on the distance between the user and the reference station (spatial correlation), the latency of differential corrections (temporal correlation), and the quality of differential corrections. Therefore, how to correctly generate differential corrections as well as their pricision is very important to the DGPS positioning technique. This paper presents a new algorithm for generating differential GPS corrections. This algorithm directly uses code and carrier observations in the measurement model of a Kalman filter, so that it is possible to use a simple stochastic model and to use the standard algorithm of the Kalman filter. The algorithm accounts for biases like multipath errors and instrumental delays in code observations and it shows how differential corrections are differently affected by code biases when dual or single frequency data is used. In addition, the algorithm can be integrated with a real time quality control procedure. As a result, the quality of differential corrections can be guaranteed with a certain probability.     

北斗/超宽带组合定位的室内外过渡区无缝链接方法

室内外无缝导航定位是万物互联之基石,具有广阔的市场前景和应用价值. 但目前对于室内外过渡区的无缝组合导航技术,仍存在诸多棘手问题亟待解决. 对此,从三个方面对BDS/UWB组合定位的室内外无缝链接方法进行了改进:一是提出了一种基于内引法和外引法的室内信标绝对定位方法,以解决室内外定位结果的坐标基准统一问题;二是提出了一种基于位置精度因子(PDOP)平稳变化的室内信标优化布局方案,以提高过渡区域的导航定位精度与信标可用性;三是提出引入自适应权重因子,来解决BDS/UWB组合定位的观测值合理定权问题. 通过具体实验验证:1) 利用基于内引法和外引法的室内信标绝对定位方法,可实现室内外坐标基准的统一,显著提高了用户使用的便捷性;2) 采用所提信标优化布局方案,可有效提高过渡区定位精度,相比无超宽带(UWB)信标,BDS/UWB组合定位的平均定位精度至少提高 355%;3) 自适应权重因子可实时调节不同时间、不同类型观测值的权比,增强了观测信息利用效率,相比北斗卫星导航系统(BDS)空旷区域,定位精度可至少提高22.5%.      

RTK差分技术在网约车计费系统检测中的应用

2013年以来,随着打车软件的流行,网络约车不断进入人们的视野并活跃在全国各大城市。随之而来的网络约车软件定位不准、计程不准而导致的客户投诉也接踵而来。针对这些问题,本文提出了一套网络约车计费检测方法,采用多模多频RTK载波相位差分技术和惯性导航组合定位技术,使用基准站+流动站的RTK差分GNSS接收机、惯导模块、高精度扼流圈导航天线及回放仪记录汽车行驶过程中的信息,包括经纬度、乘车时间、速度等,通过计算得出汽车行驶里程。通过与司机手机计费结果进行比较,试验结果表明,采用载波相位差分技术和组合导航定位的技术可以有效解决定位失锁、轨迹不连续等问题。     

星座异构基准站网虚拟参考站数据生成方法

针对各地现有卫星导航定位基准站可用星座存在差异性的问题,提出了按星座分别生成虚拟参考站数据的方法。该方法通过修正接收机钟差影响,实现了多个参考站作为主参考站生成同一个站点的虚拟观测值,有效避免了单个主参考站星座兼容性的影响,可为流动站提供更多的可用卫星。试验针对部分基准站不兼容北斗卫星的情况,分别在开阔区域和房角区域测试了按星座组网前后流动站的定位性能。结果显示：更多基准站参与服务能够改善虚拟参考站数据质量;按星座组网后流动站的定位质量更优,尤其可以显著改善流动站在房角等有遮挡区域的可用性和定位质量。研究成果对于有效整合当前各类基准站数据资源、提升服务对星座的兼容性具有实用价值。     

Development and testing of a new ray-tracing approach to GNSS carrier-phase multipath modelling

Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8 cm for the Global Positioning System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation, but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite–reflector–antenna geometry and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method will have important practical applications for correcting for multipath in well-constrained environments (such as at base stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can be used to simulate realistic multipath errors for various performance analyses in high-precision positioning.     

GPS snow depth meter with geometry-free linear combinations of carrier phases

Multipath in global positioning system (GPS) is the interference of the microwave signals directly from satellites and those reflected before reaching the antenna, typically by the ground. Because reflected signals cause positioning errors, GPS antennas are designed to reduce such interference. Recent studies show that multipath could be utilized to infer the properties of the ground around the antenna. Here, we report one such application, i.e. a fixed GPS station used as a snow depth meter. Because the satellite moves in the sky, the excess path length of reflected waves changes at rates dependent on the antenna height. This causes quasi-periodic variations of the amplitude and phase of the received signals. Accumulation of snow reduces effective antenna heights, and we can see it by analyzing multipath signatures. Signal-to-noise ratios (SNR) are often used to analyze multipath, but they are not always available in raw GPS data files. Here, we demonstrate that the geometry-free linear combination (L4), normally used to study the ionosphere, can also be used to analyze multipath signatures. We obtained snow depth time series at a GPS station in Hokkaido, Japan, from January to April in 2009 using L4 and SNR. Then, we compared their precisions. We also discuss mechanisms responsible for the possible underestimation of the snow depth by GPS. Finally, we investigate the possibility of inferring physical conditions of the snow surface using amplitudes of multipath signatures.     

长距离网络RTK实时厘米级定位算法

针对CORS系统建设成本高和选址困难的问题,该文提出GPS长距离网络RTK定位算法。该算法首先利用MW组合观测方程解算基准站双差宽巷整周模糊度,采用Saastamoinen模型和GMF映射函数模型相结合解算双差对流层干分量延迟残差,并将双差对流层湿分量延迟残差作为未知参数进行估计,同时结合无电离层组合观测值解算基准站双差载波整周模糊度;然后,采用综合误差内插法解算基准站和流动站的误差改正数;最后,采用最小二乘法逐历元进行法方程叠加解算流动站双差模糊度浮点解,并利用LAMBDA算法和通过TIKHONOV正则化改进的LAMBDA算法搜索固定流动站双差宽巷整周模糊度和双差载波整周模糊度。实验表明,该算法能够将基准站间距离提高到100~150km,使流动站用户可以获得厘米级定位结果。     

New global positioning system reference station in Brazil

Co-located very long baseline interferometry (VLBI) and global positioning system (GPS) reference stations were installed near Fortaleza, Brazil, in 1993. Both have been important in the realization and maintenance of the International Terrestrial Reference Frame. A new-generation GPS system was installed in 2005 to replace the original station. Experience gained in the prior 12 years was used to improve the design of the GPS antenna mount. Preliminary indications are greatly improved data quality from the new station. Simultaneous observations from the nearly half-year of overlapping operation have been used to determine the local tie between the new and old GPS reference points to about 1 mm accuracy. This can be used to update the 1993 survey tie between the original GPS and the VLBI points, although there are questions about the accuracy of that measurement based on a comparison with space geodetic data. A test of removing the conical radome over the old GPS antenna indicates that it has biased the station height by about 16 mm downward, which probably accounts for most of the previous survey discrepancy.