GNSS多系统组合测速模型与精度分析

基于GPS多普勒测速原理,建立了GNSS多系统组合测速数学模型,结合实测数据对GNSS多系统组合的原始多普勒测速、相位一阶中心差分导出多普勒测速及二者组合测速精度进行了分析。结果表明,GNSS多系统组合能够显著提高原始多普勒测速及导出多普勒测速的精度,同时能够在一定范围内提高原始多普勒与导出多普勒组合测速的精度;采用原始多普勒与相位导出多普勒观测值组合,GNSS单系统时能够有效地提高测速精度,GNSS多系统组合效果不明显。      

单点GPS多普勒测速模型比较与精度分析

讨论GPS单点测速的观测方程,重点讨论基于多普勒频移测速的两种方法,分析其误差来源及对测速精度的影响;然后用静态数据模拟动态测速试验,数据处理采用自编单点测速软件。通过对比分析表明,采用原始多普勒观测值进行测速时因接收机型号的不同,结果差异较大,较差者可达17cm/s左右;而采用高频导出多普勒值进行测速的精度可以达到1cm/s左右,甚至可以达到mm/s量级。     

北斗载波相位差分的高频测速

针对GNSS测速方法中,传统单站历元间伪距单点定位位置差分及原始多普勒观测实时估计载体速度精度较低的问题,该文通过GNSS模块输出的载波相位观测值,根据相位中心一阶差分导出多普勒观测值的方法、同时系统地分析参数估计中各项误差源的影响,最后通过多普勒测速原理实时估计载体的速度信息。实验结果表明,该文所采用的方法静态模式下精度可以达到1～2mm/s,动态情况下测速精度可以达到5cm/s,较好地满足了机械控制领域的测速需求。     

GPS单点测速的误差分析及精度评价

首先从理论和实测数据模拟两方面分析了SA取消后各类误差源对GPS测速的影响,推导并计算了GPS单点测速可能达到的精度水平。然后用静态数据模拟动态测速试验和实测动态数据测速与同步高精度惯导测速的动态试验进行验证。结果表明,采用载波相位导出的多普勒观测值使用静态数据模拟动态测速,其精度可以达到mm/s级;用接收机输出的多普勒观测值进行测速时,其精度为cm/s级。在动态测速试验中,GPS单点测速方法（即多普勒观测值测速与导出多普勒观测值测速）间的符合精度达到cm/s级,与高精度的惯导测速结果的符合精度为dm/s级,而且和运动载体的动态条件（如加速度和加速度变化率的大小）具有很强的相关性。     

GPS单点测速的误差分析及精度评伤

首先从理论和实测数据模拟两方面分析了sA取消后各类误差源对GPS测速的影响,推导并计算了GPs单点测速可能达到的精度水平.然后用静态数据模拟动态测速试验和实测动态数据测速与同步高精度惯导测速的动态试验进行验证.结果表明,采用栽波相位导出的多普勒观测值使用静态数据模拟动态测速,其精度可以达到mm/s级;用接收机输出的多普勒观测值进行测速时,其精度为cm/s级.在动态测速试验中,GPS单点测速方法(即多普勒观测值测速与导出多普勒观测值测速)间的符合精度达到cm/s级,与高精度的惯导测速结果的符合精度为dm/s级,而且和运动载体的动态条件(如加速度和加速度变化率的大小)具有很强的相关性.     

GPS观测值综合测速

使用GPS观测量不仅可以确定运动载体的位置，而且可以计算载体的运动速度。多普勒观测量一般用于速度的测定。多普勒观测量既有原始输出的(对于部分接收机)，也有由相位观测值导出的，而且有两种频率的观测值，它们均可以独立用于载体速度的计算，当然也可以综合起来测定载体速度，后者还未见报道，且值得探讨。本文讨论了用多种多普勒观测值综合测速的问题，给出了综合测速的数学模型，分析了其精度，评价了其优缺点，处理了实际测量数据，给出了一些结论。     

几种GPS测速方法的比较分析

GPS高精度定位结果、原始多普勒频移观测量，以及由载波相位中心差分而获得的多普勒频移观测值，它们都可以用来获得高精度的速度测量结果。主要从测速精度方面，对这3种方法进行了比较，并作算例分析。     

GPS多普勒观测值测速的精度分析

讨论了利用多普勒观测值进行单点测速的观测方程,分析了其误差来源和各误差源对测速精度的影响。用自编软件计算了静态和动态条件下GPS测速的精度,其中动态测速的参考速度采用GrafNav Version7．00软件计算得到,比较结果表明在静态和动态条件下测速精度都可以达到cm／s级     

GPS原始多普勒观测值精度评估

原始多普勒观测值可以用于测定速度、平滑伪距和周跳的探测，不论在哪个方面使用，都需要了解其精度情况，本文意在用实际测量数据来评价其测量精度，并分析测量精度与卫星高度角的关系。数据分析结果表明，原始多普勒观测值的内附合精度是1-2cm／s，外符合精度是2-3cm/s，可以推断原始多普勒观测值的精度约为2cm／s。另外原始多普勒观测值的误差与卫星高度角有关，高度角越大，误差越小，反之，高度角越小，误差越大，确切关系可以用分段函数来描述。值得说明的是这是一个针对特定试验的精度评价，有一定的参考价值，但是不具有普遍意义。     

利用GPS伪距导出的多普勒频移测速

推导了利用伪距观测值获取多普勒频移的公式,并利用导出的多普勒频移来确定载体的速度。实测数据表明,利用伪距导出的多普勒频移测速,可以达到dm/s级的水平。在没有原始多普勒观测值或者相位观测出现了频繁周跳的情况下,可以利用伪距导出的多普勒频移获得载体概略的速度信息。     

GPS单点测速的误差分析及精度评价 (英文)

Error sources which decrease the accuracy of GPS in absolute velocity determination have been changed since SA was turned off. Firstly, quantities of all kinds of error sources that influence velocity determination are analyzed. The potential accuracy of GPS absolute velocity determination is derived from both theory and field GPS data simulation. After that, two tests were carried out to evaluate the performance of GPS absolute velocity determination in the case of a static and an airborne GPS receiver and INS （Inertial Navigation System） instrument in kinematic mode. In static mode, the receiver velocity has been estimated to be several mm/s with the carrier-phase derived Doppler measurements, and several cm/s with the receiver generated Doppler measurements. In kinematic mode, GPS absolute velocity estimates are compared with the synchronized measurements from the high accuracy INS. The root mean square statistics of the velocity discrepancies between GPS and INS come up to dm/s. Moreover, it has a strong correlation with the acceleration or jerk of the aircraft.     

GPS多普勒频移测量速度模型与误差分析

利用GPS多普勒频移观测量可以获得高精度的速度测量结果。文中先给出GPS载波相位观测方程，在此基础上，详细推导了GPS多普勒频移测量载体速度的数学模型。然后在相对测量模式下，讨论各种误差对速度的影响。     

Initial results of precise orbit and clock determination for COMPASS navigation satellite system

The development of the COMPASS satellite system is introduced, and the regional tracking network and data availability are described. The precise orbit determination strategy of COMPASS satellites is presented. Data of June 2012 are processed. The obtained orbits are evaluated by analysis of post-fit residuals, orbit overlap comparison and SLR (satellite laser ranging) validation. The RMS (root mean square) values of post-fit residuals for one month’s data are smaller than 2.0 cm for ionosphere-free phase measurements and 2.6 m for ionosphere-free code observations. The 48-h orbit overlap comparison shows that the RMS values of differences in the radial component are much smaller than 10 cm and those of the cross-track component are smaller than 20 cm. The SLR validation shows that the overall RMS of observed minus computed residuals is 68.5 cm for G01 and 10.8 cm for I03. The static and kinematic PPP solutions are produced to further evaluate the accuracy of COMPASS orbit and clock products. The static daily COMPASS PPP solutions achieve an accuracy of better than 1 cm in horizontal and 3 cm in vertical. The accuracy of the COMPASS kinematic PPP solutions is within 1–2 cm in the horizontal and 4–7 cm in the vertical. In addition, we find that the COMPASS kinematic solutions are generally better than the GPS ones for the selected location. Furthermore, the COMPASS/GPS combinations significantly improve the accuracy of GPS only PPP solutions. The RMS values are basically smaller than 1 cm in the horizontal components and 3–4 cm in the vertical component.     

Precise relative positioning using real tracking data from COMPASS GEO and IGSO satellites

China completed a basic COMPASS navigation network with three Geostationary and three Inclined Geosynchronous satellites in orbit in April 2011. The network has been able to provide preliminary positioning and navigation functions. We first present a quality analysis using 1-week COMPASS measurements collected in Wuhan. Satellite visibility and validity of measurements, carrier-to-noise density ratio and code noise are analyzed. The analysis of multipath combinations shows that the noise level of COMPASS code measurements is higher than that of GPS collected using the same receiver. Second, the results of positioning are presented and analyzed. For the standalone COMPASS solutions, an accuracy of 20 m can be achieved. An accuracy of 3.0 m for the vertical, 1.5 m for the North and about 0.6–0.8 m for the East component is obtained using dual-frequency code only measurements for a short baseline. More importantly, code and phase measurements of the short baseline are processed together to obtain precise relative positioning. Kinematic solutions are then compared with the ground truth. The precision of COMPASS only solutions is better than 2 cm for the North component and 4 cm for the vertical. The standard deviation of the East component is smaller than 1 cm, which is even better than that of the East component of GPS solutions. The accuracy of GPS/COMPASS combination solutions is at least 20 % better than that of GPS alone. Furthermore, the geometry-based residuals of double differenced phase and code measurements are analyzed. The analysis shows that the noise level of un-differenced phase measurements is about 2–4 mm on both B1 and B2 frequencies. For the code measurements, the noise level is less than 0.45 m for B1 CA and about 0.35 m for B2 P code. Many of the COMPASS results presented are very promising and have been obtained for the first time.     

顾及卫星非圆轨道改正的GNSS精密测速方法

详细推导了卫星非圆轨道改正的计算公式,给出高精度测速顾及该项误差的处理策略．采用全球均匀分布的12个国际GNSS服务（IGS）测站的多普勒和载波相位观测数据,仿动态评估了该项误差对测速精度的影响．结果表明:基于历元间载波相位差分的测速方法,改正后东、北、天顶方向分别提高8％、9％和10％,三维测速精度从9.9 mm／s改正到8.9 mm／s;基于原始多普勒的测速方法,东、北方向与载波相位差分方法的改正数值基本一致,天顶方向约是载波相位差分方法的改正数值的一半．      

星载BDS/GPS低轨卫星定轨精度分析

针对低轨卫星搭载BDS/GPS接收机实现定轨将成为定轨领域热点的现状,该文讨论了基于星载BDS/GPS实时定轨和精密定轨需要考虑的数学模型,阐述了实时定轨和精密定轨的模型差异。基于自主研发程序,利用高动态信号仿真器仿真的星载BDS/GPS数据研究了基于星载BDS/GPS实时定轨和精密定轨的可行性及其能达到的精度。试验结果表明,星载BDS/GPS实时定轨位置精度为1.19m,速度精度为2.35mm/s。GPS信号发生中断时即仅采用BDS观测数据进行实时定轨时,三维位置误差达到3.73m;星载BDS/GPS精密定轨位置精度为2.30cm,仅采用BDS观测数据进行精密定轨时,三维位置误差可达到8.26cm。