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1.
The network-based real-time kinematic (RTK) positioning has been widely used for high-accuracy applications. However, the precise point positioning (PPP) technique can also achieve centimeter to decimeter kinematic positioning accuracy without restriction of inter-station distances but is not as popular as network RTK for real-time engineering applications. Typically, PPP requires a long initialization time and continuous satellite signals to maintain the high accuracy. In case of phase breaks or loss of signals, re-initialization is usually required. An approach of instantaneous cycle slips fixing using undifferenced carrier phase measurements is proposed, which leads to instantaneous re-initialization for real-time PPP. In the proposed approach, various errors such as real-time orbit and clock errors, atmosphere delay and wind-up effects are first refined and isolated from integer cycle slips. The integer values of cycle slips can then be estimated and fixed with the LAMBDA technique by applying a cascade cycle slip resolution strategy. Numerical experiments with different user dynamics are carried out to allow a comprehensive evaluation of efficiency and robustness of the cycle slip fixing algorithm. The results show that the cycle slips can be fixed correctly in all cases considered and that data gaps of up to 300?s can be connected with high confidence. As a result, instantaneous re-initialization is achieved in the real-time PPP processing. 相似文献
2.
GNSS精密单点定位中的实时质量控制 总被引：2，自引：1，他引：1
提出了一套适用于GNSS精密单点定位(PPP)的实时质量控制方法,重点研究了钟跳探测与修复、周跳探测与标记、抗差估计方法,并在现有质量控制方法的基础上进行了改进。对比分析了不同质量控制方案对PPP的影响,结果表明,钟跳不利于周跳探测,严重影响非差PPP的精度和效率,必须对其进行探测与修复;联合MW、GF组合可以探测出绝大多数周跳,且较使用单一方法更为准确、可靠;采用改进的抗差估计有效抑制了残余粗差对精密定位的影响,显著提高了PPP的精度和可靠性。 相似文献
3.
非组合精密单点定位算法精密授时的可行性研究 总被引：4，自引：1，他引：3
利用基于GPS双频原始观测数据的非组合精密单点定位(PPP)算法进行精密授时,给出了其数学模型与数据预处理策略。实验结果表明,非组合PPP算法可以有效避免传统PPP算法由于观测值组合过程中观测噪声及多路径效应误差被放大而造成的对接收机钟差解算的不利影响,实现亚纳秒级(0.3 ns)的钟差解算精度;同等条件下,非组合PPP算法授时精度优于传统PPP算法,可以用于精密授时解算。 相似文献
4.
Since the Selective Availability was turned off, the velocity and acceleration can be determined accurately with a single GPS receiver using raw Doppler measurements. The carrier-phase-derived Doppler measurements are normally used to determine velocity and acceleration when there is no direct output of the raw Doppler observations in GPS receivers. Due to GPS receiver clock drifts, however, a GPS receiver clock jump occurs when the GPS receiver clock resets itself (typically with 1 ms increment/decrement) to synchronize with the GPS time. The clock jump affects the corresponding relationship between measurements and their time tags, which results in non-equidistant measurement sampling in time or incorrect time tags. This in turn affects velocity and acceleration determined for a GPS receiver by the conventional method which needs equidistant carrier phases to construct the derived Doppler measurements. To overcome this problem, an improved method that takes into account, GPS receiver clock jumps are devised to generate non-equidistant-derived Doppler observations based on non-equidistant carrier phases. Test results for static and kinematic receivers, which are obtained by using the conventional method without reconstructing the equidistant continuous carrier phases, show that receiver velocity and acceleration suffered significantly from clock jumps. An airborne kinematic experiment shows that the greatest impact on velocity and acceleration reaches up to 0.2 m/s, 0.1 m/s2 for the horizontal component and 0.5 m/s, 0.25 m/s2 for the vertical component. Therefore, it can be demonstrated that velocity and acceleration measurements by using a standalone GPS receiver can be immune to the influence of GPS receiver clock jumps with the proposed method. 相似文献
5.
The International Atomic Time scale (TAI) is computed by the Bureau International des Poids et Mesures (BIPM) from a set of
atomic clocks distributed in about 40 time laboratories around the world. The time transfer between these remote clocks is
mostly performed by the so-called GPS common view method: The clocks are connected to a GPS time receiver whose internal software
computes the offsets between the remote clocks and GPS time. These data are collected in a standard formal called CCTF. In
the present study we develop both the procedure and the software tool that allows us to generate the CCTF files needed for
time transfer to TAI, using RINEX files produced by geodetic receivers driven by an external frequency. The CCTF files are
then generated from the RINEX observation files. The software is freely available at ftp://omaftp.oma.be/dist/astro/time/RINEX_CCTF.
Applied to IGS (International GPS Service) receivers, this procedure will provide a direct link between TAI and the IGS clock
combination. We demonstrate here the procedure using the RINEX files from the Ashtech Metronome (ZXII-T) GPS receiver, to
which we apply the conventional analysis to compute the CCTF data. We compared these results with the CCTF files produced
by a time receiver R100-30T from 3S-Navigation. We also used this comparison with the results of a calibrated time receiver
to determine the hardware delay of the geodetic receiver. ? 2001 John Wiley & Sons, Inc. 相似文献
6.
在复杂观测环境下,GNSS信号容易发生周跳和失锁现象,导致精密单点定位技术（PPP）模糊度重新初始化,影响定位精度及可靠性。本文基于PPP／SINS紧组合,提出了利用短时间内惯导递推的高精度位置信息辅助PPP周跳修复的几何模型。该模型采用原始观测值建立历元间差分方程,将周跳作为参数进行估计,而惯导提供的高精度位置作为带权的虚拟观测值参与平差解算,在固定周跳整数值后修复相位观测值,从而保持高精度的连续定位。以车载和机载两组数据分析了该方法的有效性,结果表明,引入惯性辅助能够显著加快PPP定位的重新收敛,实现周跳的准确修复。 相似文献
7.
8.
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). 相似文献
9.
DAI LiwenHAN ShaoweiChris Rizos 《地球空间信息科学学报》2001,4(4):9-18
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10.
11.
利用精密星历进行单点定位的数学模型和初步分析 总被引：14，自引：1，他引：14
精密单点定位(Precise Point Positioning,简称PPP),是相对于一般的单点定位而言的,它是利用GPS的精密星历和钟差文件,以载波相位和伪距为观测资料,进行独立的单点精密定位.它的特点在于各站的解算相互独立,计算量远远小于一般的相对定位.尝试以伪距为观测值,利用JPL给出的精密星历(*.sp3)和钟差(*.clk),进行精密单点定位的试验,取得了初步的结果. 相似文献
12.
Time-relative positioning is a recent method for processing GPS phase observations. The operational method undertaken in this
paper consists of the following steps: first, recording phase observations at a station of known coordinates; second, moving
the GPS receiver to an unknown station (which can be located up to a few hundred meters away, dependint on what type of transportation
– e. g., walking, motorcycle – is available) while continuously observing carrier phases; and, third, recording phase observations
at a second station of unknown coordinates with a single GPS receiver. To obtain the position of the unknown station relative
to the first (known) station, the processing method uses combined observations taken at two different epochs and two different
stations with the same receiver. For this reason, the errors that vary between two epochs must be taken into account in an
appropriate way, especially errors in satellite clock corrections and ephemerides, and errors related to tropospheric and
ionospheric delays. Ionospheric modeling using IONEX files (the ionospheric maps calculated by the International GPS Service)
was also tested to correct L1 phase observations. This method has been used to calculate short vectors with an accuracy of
a few centimeters (for a processing interval of 30 s) using a single civil GPS receiver. ? 2001 John Wiley & Sons, Inc. 相似文献
13.
14.
Currently, the GNSS computing modes are of two classes: network-based data processing and user receiver-based processing. A GNSS reference receiver station essentially contributes raw measurement data in either the RINEX file format or as real-time data streams in the RTCM format. Very little computation is carried out by the reference station. The existing network-based processing modes, regardless of whether they are executed in real-time or post-processed modes, are centralised or sequential. This paper describes a distributed GNSS computing framework that incorporates three GNSS modes: reference station-based, user receiver-based and network-based data processing. Raw data streams from each GNSS reference receiver station are processed in a distributed manner, i.e., either at the station itself or at a hosting data server/processor, to generate station-based solutions, or reference receiver-specific parameters. These may include precise receiver clock, zenith tropospheric delay, differential code biases, ambiguity parameters, ionospheric delays, as well as line-of-sight information such as azimuth and elevation angles. Covariance information for estimated parameters may also be optionally provided. In such a mode the nearby precise point positioning (PPP) or real-time kinematic (RTK) users can directly use the corrections from all or some of the stations for real-time precise positioning via a data server. At the user receiver, PPP and RTK techniques are unified under the same observation models, and the distinction is how the user receiver software deals with corrections from the reference station solutions and the ambiguity estimation in the observation equations. Numerical tests demonstrate good convergence behaviour for differential code bias and ambiguity estimates derived individually with single reference stations. With station-based solutions from three reference stations within distances of 22–103 km the user receiver positioning results, with various schemes, show an accuracy improvement of the proposed station-augmented PPP and ambiguity-fixed PPP solutions with respect to the standard float PPP solutions without station augmentation and ambiguity resolutions. Overall, the proposed reference station-based GNSS computing mode can support PPP and RTK positioning services as a simpler alternative to the existing network-based RTK or regionally augmented PPP systems. 相似文献
15.
Weiwei Song Wenting Yi Yidong Lou Chuang Shi Yibin Yao Yanyan Liu Yong Mao Yu Xiang 《GPS Solutions》2014,18(3):323-333
GLONASS carrier phase and pseudorange observations suffer from inter-channel biases (ICBs) because of frequency division multiple access (FDMA). Therefore, we analyze the effect of GLONASS pseudorange inter-channel biases on the GLONASS clock corrections. Different Analysis Centers (AC) eliminate the impact of GLONASS pseudorange ICBs in different ways. This leads to significant differences in the satellite and AC-specific offsets in the GLONASS clock corrections. Satellite and AC-specific offset differences are strongly correlated with frequency. Furthermore, the GLONASS pseudorange ICBs also leads to day-boundary jumps in the GLONASS clock corrections for the same analysis center between adjacent days. This in turn will influence the accuracy of the combined GPS/GLONASS precise point positioning (PPP) at the day-boundary. To solve these problems, a GNSS clock correction combination method based on the Kalman filter is proposed. During the combination, the AC-specific offsets and the satellite and AC-specific offsets can be estimated. The test results show the feasibility and effectiveness of the proposed clock combination method. The combined clock corrections can effectively weaken the influence of clock day-boundary jumps on combined GPS/GLONASS kinematic PPP. Furthermore, these combined clock corrections can improve the accuracy of the combined GPS/GLONASS static PPP single-day solutions when compared to the accuracy of each analysis center alone. 相似文献
16.
TEQC: The Multi-Purpose Toolkit for GPS/GLONASS Data 总被引：31，自引：11，他引：20
17.
GPS非差相位精密单点定位技术探讨 总被引：77，自引：12，他引：77
探讨了精密单点定位的基本原理，处理方法，所涉及的误差改正及数据处理中的一些关键技术；采用直接内插IGS卫星精密星历的方法代替利用IGS跟踪站进行轨道精化方法计算卫星轨道参数，对现有精密单点定位计算方法进行了简化，使之更具有实用性。最后利用自主研发的精密非差单点定位软件计算和分析了实测数据。计算结果表明，经过大约15min的初始化后，非差相位单历元的定位结果精确度在X，Y，Z方向上均优于20cm。 相似文献
18.
精密卫星钟差加密方法及其对星载GPS低轨卫星定轨精度影响 总被引：7，自引：0，他引：7
韩保民 《武汉大学学报(信息科学版)》2006,31(12):1075-1078
系统分析、比较了几种精密卫星钟差加密方法，研究了利用全球分布的IGS永久跟踪站的GPS观测数据估计高采样率卫星钟差参数的原理与方法，并将各种卫星钟差加密方法得到的结果与IGS数据分析中心估计的卫星钟差结果相比较。最后将不同加密方法得出的精密卫星钟差结果用于基于星载GPS双频非差观测值的CHAMP低轨卫星的定轨，并将不同方法得到的定轨精度进行比较。结果表明，利用地面跟踪站的GPS观测数据，可高精度、高密度地估计GPS卫星钟差，估计精度可达0．1～0．5ns。经地面GPS跟踪站数据估计的GPS卫星钟差，应用于基于PPP方法的低轨卫星定轨，其定轨精度在10cm以内。 相似文献
19.
广域实时精密定位与时间服务已成为GNSS应用领域研究热点,目前国内外学者围绕其模型算法已展开大量的研究。本文重点论述广域实时精密定位与时间服务数据的处理方法和服务系统,给出了基于不同基准约束的卫星钟差解算数学模型,提出通过引入外接原子钟测站、标准时间源(UTC/BDT)等不同时间基准,构建卫星拟稳基准、外接原子钟跟踪站拟稳基准及标准时间源等约束下的钟差解算模型,分析了时间基准对精密单点定位和精密单点授时的影响。本文采用实时卫星轨道、钟差、相位偏差、电离层延迟等服务产品及跟踪站实时数据,验证了系统产品可靠性及终端定位与时间服务性能。实测结果表明:GPS轨道径向精度1.8 cm,钟差STD精度约0.05 ns;BDS-3轨道径向精度6.7 cm,钟差STD精度优于0.1 ns;GPS和BDS-2电离层改正精度分别为0.74 TECU与1.03 TECU。基于该产品实现了用户端PPP、PPP-RTK及PPT、PPT-RTK服务,满足了用户实时厘米级定位和优于0.5 ns的单站时间传递服务,当采用GPS+BDS-2 PPP-RTK解算时,平面收敛至5 cm约需要12 min。 相似文献
20.
在传统多系统非差非组合精密单点定位（precise point positioning,PPP）模型中,电离层延迟会吸收部分接收机码硬件延迟,其估计值可能为负数。提出了一种估计接收机差分码偏差（differential code bias,DCB）参数的GPS（Global Positioning System）/BDS（BeiDou Navigation Satellite System）非组合PPP模型,将每个系统第1个频率上的接收机码硬件延迟约束为零,对接收机DCB进行参数估计,达到了分离电离层延迟和接收机码硬件延迟的目的,降低了接收机钟差和电离层延迟的相关程度。利用4个多星座实验（multi-GNSS experiment,MGEX）跟踪站的GPS/BDS数据进行了静态和动态PPP试验,结果表明,与不估计DCB参数的PPP模型相比,采用估计DCB参数PPP模型后,静态模式下定位精度和收敛速度平均提高了29.3%和29.8%,动态模式下定位精度和收敛速度平均提高了15.7%和21.6%。 相似文献