在线PPP软件的精度比较分析

对目前存在的在线免费PPP软件进行了介绍,并用实际算例对这些在线免费PPP软件进行了测试,综合比较了在线免费PPP软件的特点,分析其精度特性,得出了一些值得参考的结论。     

利用非组合精密单点定位提取区域电离层延迟及其精度评定

提出了一种利用非组合精密单点定位（PPP）提取区域电离层延迟的方法,并将区域电离层延迟内插至用户站实施单频仿动态PPP,以检验电离层延迟的提取精度。结果表明,电离层延迟内插精度受电离层活动变化影响较小,2 d内均能保证优于1 dm;单频仿动态PPP的定位精度在平面方向约为4~5 cm,高程方向优于1 dm;为便于比较分...     

附加区域电离层约束的PPP定位收敛性分析

为了改善PPP的定位精度和收敛速度,提出一种有效的解决思路：在非差非组合模型PPP定位的基础上,附加高精度区域电离层先验信息约束,利用美国西海岸CORS网内183个参考站的观测数据进行区域电离层建模,获取高精度电离层延迟信息;通过实验对比分析无电离层组合模型、非差非组合模型和附加电离层约束的非差非组合模型3种算法的PPP定位表现,结果表明,附加电离层约束算法具有更好的模型几何强度,相比于前两种模型,在PPP定位过程前10 min,该算法可以显著提升PPP定位的收敛速度和定位精度。     

基于北斗的精密单点定位估计对流层天顶延迟精度分析

通过全球导航卫星（GNSS）系统获取对流层天顶延迟对于气象和电波折射修正具有重要应用价值。利用自主研发的静态精密单点定位软件CRPPP,基于国际GNSS地球动力学服务局（IGS）发布的北斗系统（BDS）精密星历和精密钟差,给出了BDS估算天顶延迟结果。以IGS发布的全球定位系统（GPS）结果为参考对比,BDS估算天顶延迟结果平均偏差优于5mm,均方根误差（rms）优于2．3cm．同时,给出了西沙地区GPS与BDS估计结果,结果表明：利用北斗系统估计的对流层天顶延迟精度与GPS相当。     

利用精密单点定位（PPP）方法在黑龙江省进行1∶10000像片控制测量的精度分析

通过对黑龙江省某测区利用GPS静态网和精密单点定位（PPP）两种方法对1∶10 000像片控制测量成果进行对比分析,在利用CQG2000对大地高进行高程异常改算精度同传统GPS网拟合高程进行对比分析。通过对比分析得出结论：精密单点定位（PPP）方法施测的像控点平面精度能够满足1∶10 000地形图更新、山区1∶10 000地形图测绘中±1 m的精度要求。同时也验证了＂我国大陆重力大地水准面CQG2000绝对精度在东经120°以东高于±0.3 m的可靠性。     

精密单点定位技术在困难地区重力调查中的应用

概述了精密单点定位的原理,结合困难地区重力调查的实际情况详细介绍了利用精密单点定位获取该地区重力测点平面坐标和正常高的技术路线及方法,为精密单点定位应用于重力调查困难地区提供参考。     

LEO星座增强GNSS的精密单点定位初步分析

本文选取GPS系统和Iridium系统，采用数学仿真技术初步分析了LEO星座对GNSS在精密单点定位中的增强作用。在仿真了BJFS站GPS和Iridium观测数据的基础上进行Iridium增强GPS的伪动态下精密单点定位实验，结果表明：与GPS单系统相比，GPS＋Iridium双系统的可视卫星数平均增加1.5颗，GDOP值和PDOP值降低0.25左右；Iridium增强GPS后PPP滤波矩阵的条件数快速减小，提升了PPP滤波矩阵的稳定性，提高了天顶U方向的定位精度，从而提高了三维的定位精度，PPP收敛时间缩短了30%以上；采用单差MW法固定PPP模糊度，分别以Ratio=1.5、3、5作为模糊度固定成功的指标，并与模糊度仿真值对比，PPP模糊度首次固定成功所需的时间缩短40%以上。     

Ocean Tides Observed from A GPS Receiver on Floating Sea Ice Near Chinese Zhongshan Station,Antarctica

Due to limit of coverage in TOPEX/Poseidon (T/P) satellite and sparseness of in-situ tide gauges around Antarctica, the accuracy of global ocean tide models in Antarctic seas is relatively poorer than in low- and mid-latitude regions. To better understand ocean tides in Prydz Bay, east Antarctica, a GPS receiver was deployed on floating sea ice to measure tide-induced ice motion in multiple campaigns. Four online Precise Point Positioning (PPP) services are used to process the GPS data in the kinematic PPP mode, and UTide software is used to separate the major tidal constituents. Comparison between results from different processing methods (relative processing solutions from Track, kinematic PPP solutions from online services) and with bottom pressure gauge (BPG) shows that, high-accuracy tidal information can be obtained from GPS observations on floating sea ice, the root-sum-square (RSS) for the eight major constituents (O1, K1, P1, Q1, M2, S2, N2, K2) is below 4 cm. We have also studied the impacts of data span and filter edge effects at daily boundaries on the accuracy of tide estimates, and found that to obtain reliable tide estimates and neglect the filter edge effects, continuous observation longer than 30 days is necessary. Our study suggests that GPS provides an independent method to estimate tides in Prydz Bay, and can be an alternative to tidal gauges, which are costly and hard to maintain in Antarctica.     

电离层高阶项延迟对多系统PPP的影响

计算位于不同纬度的3个MGEX测站在不同太阳活动及地磁场活动情况下GPS、GLONASS、Beidou和Galileo卫星导航定位系统的电离层高阶项(HOI)延迟，分析高阶项延迟对多系统PPP结果的影响，总结不同太阳活动和地磁活动对PPP的影响。结果表明，电离层延迟随纬度的增加而减小；太阳活动是影响电离层高阶项延迟的主要因素，在太阳活动指数较低时，二阶项延迟不超过2 cm，三阶项延迟约为1 mm；当太阳指数较高时，二阶项延迟超过2.5 cm，三阶项延迟可达到5 mm；当磁暴发生时，高阶项延迟会存在一定程度的增长。将电离层高阶项延迟改正后，太阳活动指数较低时点位精度提升效果明显。     

Determination of Ocean Tide Loading Displacement by GPS PPP with Priori Information Constraint of NAO99b Global Ocean Tide Model

The published global ocean tide models show good agreement in deep oceans and exhibit differences in complex coastal areas, along with subsequent Ocean Tide Loading Displacement (OTLD) modeling differences. Meanwhile, OTLD parameters (amplitudes and phase lags) derived by Global Positioning System (GPS) Precise Point Positioning (PPP) approach need long time to converge to a stable state and show poor precision of S2, K1, and K2 constituents. Based on the fact that no constraint is imposed in the current kinematic solution, a new method is put forward, in which global ocean tide model predictions are taken as the priori information constraints to speed up the convergence rate and improve the accuracy of the GPS-derived OTLD parameters. First, the data of tide gauge from 01 January 2014 to 31 December 2016 are used to generate the harmonic parameters to evaluate the accuracy of six global ocean tide models and a regional ocean tide model (osu.chinesea.2010). Osu.chinesea.2010 model shows good agreement with the tide gauge results, while NAO99b model presents relatively large difference. The predictions from osu.chinesea.2010 and NAO99b model are employed as reference and the prior information, respectively. Second, continuous observations of 12 GPS sites during 2006–2013 in Hong Kong are collected to generate three dimensional OTLD amplitudes and phase lags of eight constituents using PPP with prior information constraints approach and harmonic analysis. Third, comparing the convergence time of eight constituents from PPP without and with priori information constraints approaches, the results show that the new method can significantly improve the convergence rate of OTLD amplitude estimates which obtain a certain level of stability seven years earlier than that derived by the PPP without priori information constraints. Precision of OTLD parameters derived by the new method is about 1 mm. By comparing with the precision of single PPP approach, the accuracy of eight constituents has been improved, especially for S2, K1, and K2 constituents. Finally, through comparing the different correction effects of OTLD estimates on the coordinates and their time series of the ground GPS stations, the results show that OTLD estimates derived by the new approach have similar influence as the osu.chinasea.2010 ocean tide model. The new method provides an effective means to improve the convergence and precision of the GPS-derived OTLD parameters, and achieve a similar correction as the high precision ocean tide model.