共查询到20条相似文献，搜索用时 875 毫秒
1.
Network-based ambiguity resolution (AR) between reference stations is the prerequisite to realize a precise real-time kinematic positioning service. With the help of BDS triple-frequency signals, we can efficiently deal with the ionospheric delay and tropospheric delay, and achieve rapid and reliable AR. To overcome the inaccurate ionospheric delay estimated by the geometry-free three carrier ambiguity resolution (GF TCAR) technique, which leads to failure in the original ambiguity resolution, we propose an ionospheric-free (IF) TCAR method to resolve the ambiguity between the reference stations over long baselines. Taking full advantage of the known positions of the reference stations, the easily resolved extra-wide-lane (EWL) ambiguity, and the IF phase combinations, we can reliably fix the wide-lane (WL) ambiguity. A Kalman filter is applied to estimate precise IF ambiguities and the original ambiguity is resolved with the fixed WL ambiguity. A numerical analysis with triple-frequency BDS data from three long baselines of a CORS network is provided to compare the AR performance of GF TCAR with that of IF TCAR. The results show that both methods can reliably resolve the WL ambiguity with a remarkable correctly-fixed rate of higher than 99%, and the reliably-fixed rates of the IF TCAR slightly increase from 92.19, 94.67 and 94.61–98.26, 99.54 and 97.51% for the three baselines. Herein “correctly-fixed” and “reliably-fixed” mean the difference between the float ambiguity and the true one are less than ± 0.5 and ± 0.25 cycles, respectively. On the other hand, the AR performance of the original signals with the IF TCAR method is much better than that with the GF TCAR method attaining a 100% correctly-fixed rate, while the GF TCAR method can hardly fix the original ambiguity with the largest bias being as much as 4 cycles because of the amplified systematic bias. 相似文献
2.
Yanming Feng 《Journal of Geodesy》2008,82(12):847-862
This paper presents a general modeling strategy for ambiguity resolution (AR) and position estimation (PE) using three or
more phase-based ranging signals from a global navigation satellite system (GNSS). The proposed strategy will identify three
best “virtual” signals to allow for more reliable AR under certain observational conditions characterized by ionospheric and
tropospheric delay variability, level of phase noise and orbit accuracy. The selected virtual signals suffer from minimal
or relatively low ionospheric effects, and thus are known as ionosphere-reduced virtual signals. As a result, the ionospheric parameters in the geometry-based observational models can be eliminated for
long baselines, typically those of length tens to hundreds of kilometres. The proposed modeling comprises three major steps.
Step 1 is the geometry-free determination of the extra-widelane (EWL) formed between the two closest L-band carrier measurements,
directly from the two corresponding code measurements. Step 2 forms the second EWL signal and resolves the integer ambiguity
with a geometry-based estimator alone or together with the first EWL. This is followed by a procedure to correct for the first-order
ionospheric delay using the two ambiguity-fixed widelane (WL) signals derived from the integer-fixed EWL signals. Step 3 finds
an independent narrow-lane (NL) signal, which is used together with a refined WL to resolve NL ambiguity with geometry-based
integer estimation and search algorithms. As a result, the above two AR processes performed with WL/NL and EWL/WL signals
respectively, either in sequence or in parallel, can support real time kinematic (RTK) positioning over baselines of tens
to hundreds of kilometres, thus enabling centimetre-to-decimentre positioning at the local, regional and even global scales
in the future. 相似文献
3.
提出了一种顾及电离层约束的非差周跳实时探测与修复方法。通过构造3个线性无关的组合观测量,按逐级模糊度确定的思路,分别对超宽巷、宽巷和窄巷进行探测与修复;然后联合三步的探测结果,将周跳恢复到原始载波值上。在宽巷组合上进行了改进,将宽巷波长放大了5.34倍(GPS为3.4倍),由于窄巷波长较短需考虑电离层的影响,对不敏感周跳组合引入电离层残差法辅助窄巷的探测与修复。实验结果表明,该方法能够有效地进行周跳的实时探测和修复。 相似文献
4.
In this paper a MATLAB toolbox for determining the attitude of a rigid platform by means of multiple non-dedicated antennas
using global positioning system is presented. The programs embedded in this toolbox cover the RINEX data analysis, single
point positioning, differential positioning, coordinate conversion, attitude determination, and other auxiliary functions.
After forming the baselines through double-differenced (carrier phase smoothed) code observables, the attitude parameters
are obtained by applying the direct attitude computation and the least squares attitude estimation. The theoretical background
is summarized, and some hints regarding the software implementation are given in the paper. Moreover, improvements yielding
an expanded functionality are proposed.
相似文献
| Zhen DaiEmail: |
5.
北斗卫星导航系统播发3个频点的导航信号,有利于载波相位模糊度解算。鉴于传统的三频模糊度解算方法由于受基线距离的限制难以在中长基线情形下可靠地固定模糊度,本文提出一种适用于北斗卫星系统中长基线模糊度固定的新方法。实验结果表明,改进的新算法不受基线长度的约束,在保证超宽巷、宽巷模糊度正确固定的同时,宽巷模糊度估值误差在0.3周以内;窄巷模糊度估值误差在3周以内。相比于传统算法,新方法的改进效果较好。 相似文献
6.
The architecture of the ultra-tight GPS/INS/PL integration is the key to its successful performance; the main feature of this
architecture is the Doppler feedback to the GPS receiver tracking loops. This Doppler derived from INS, when integrated with
the carrier tracking loops, removes the Doppler due to vehicle dynamics from the GPS/PL signal thereby achieving a significant
reduction in the carrier tracking loop bandwidth. The bandwidth reduction provides several advantages such as: improvement
in anti-jamming performance, and increase in post correlated signal strength which in turn increases the dynamic range and
accuracy of measurements. Therefore, any degradation in the derived Doppler estimates will directly affect the tracking loop
bandwidth and hence its performance. The quadrature signals from the receiver correlator, I (in-phase) and Q (quadrature),
form the measurements, whereas the inertial sensor errors, position, velocity and attitude errors form the states of the complementary
Kalman filter. To specify a reliable measurement model of the filter for this type of integrated system, a good understanding
of GPS/PL signal characteristics is essential. It is shown in this paper that phase and frequency errors are the variables
that relate the measurements and the states in the Kalman filter. The main focus of this paper is to establish the fundamental
mathematical relationships that form the measurement model, and to show explicitly how the system error states are related
to the GPS/PL signals. The derived mathematical relationships encapsulated in a Kalman filter, are tested by simulation and
shown to be valid.
相似文献
| Ravindra Babu (Corresponding author)Email: |
| Jinling WangEmail: |
7.
Oliver Montenbruck Miquel Garcia-Fernandez Yoke Yoon Steffen Schön Adrian Jäggi 《GPS Solutions》2009,13(1):23-34
Phase center variations of the receiver and transmitter antenna constitute a remaining uncertainty in the high precision orbit
determination (POD) of low Earth orbit (LEO) satellites using GPS measurements. Triggered by the adoption of absolute phase
patterns in the IGS processing standards, a calibration of the Sensor Systems S67-1575-14 antenna with GFZ choke ring has
been conducted that serves as POD antenna on various geodetic satellites such as CHAMP, GRACE and TerraSAR-X. Nominal phase
patterns have been obtained with a robotic measurement system in a field campaign and the results were used to assess the
impact of receiver antenna phase patterns on the achievable positioning accuracy. Along with this, phase center distortions
in the actual spacecraft environment were characterized based on POD carrier phase residuals for the GRACE and TerraSAR-X
missions. It is shown that the combined ground and in-flight calibration can improve the carrier phase modeling accuracy to
a level of 4 mm which is close to the pure receiver noise. A 3.5 cm (3D rms) consistency of kinematic and reduced dynamic
orbit determination solutions is achieved for TerraSAR-X, which presumably reflects the limitations of presently available
GPS ephemeris products. The reduced dynamic solutions themselves match the observations of high grade satellite laser ranging
stations to 1.5 cm but are potentially affected by cross-track biases at the cm-level. With respect to the GPS based relative
navigation of TerraSAR-X/TanDEM-X formation, the in-flight calibration of the antenna phase patterns is considered essential
for an accurate modeling of differential carrier phase measurements and a mm level baseline reconstruction.
相似文献
| Oliver MontenbruckEmail: |
8.
Analysis of inversion errors of ionospheric radio occultation 总被引：3，自引：0，他引：3
The retrieved electron density profile of ionospheric radio occultation (RO) simulation data can be compared with the background
model value during the simulation and the inversion error can be obtained exactly. This paper studies the inversion error
of ionospheric RO through simulation. The sources of the inversion errors are analyzed. The impacts of measurement errors,
such as the errors in phase measurements and satellite orbits, are very small and can be neglected. The approximation of straight-line
propagation introduces errors at the height of the F1 layer under solar maximum condition. The spherical symmetry approximation
of the electron density distribution is found to be the main source of the inversion error. The statistical results reveal
some characteristics of the inversion errors. (1) The relative error increases with enhanced solar activity. (2) It is larger
in winter than in equinox season, and it is smallest in summer. (3) For all seasons, it is smaller at middle latitude than
at other latitudes. (4) For all seasons and geomagnetic latitudes, it is smaller at daytime than at other times. The NmF2
of the ROs from COSMIC are compared with the measurements of ionosondes, and the relative differences show the same dependencies
on season, geomagnetic latitude and local time, as the relative errors of the simulated ionospheric ROs.
相似文献
| Xiaocheng WuEmail: |
9.
Pitch and roll attitude estimation of a small-scaled helicopter using single antenna GPS with gyroscopes 总被引：2，自引：2，他引：0
A method is presented for estimating the roll and pitch attitude of a small-scaled unmanned helicopter based on the velocity
measurements of the global positioning system (GPS). The small-scaled helicopter is a radio controlled (RC) model which is
readily available and affordable for academic laboratories as a research platform. Only one single antenna GPS receiver is
equipped on the RC helicopter to acquire the velocity measurements needed for the attitude estimation. The velocity information
is recorded by the onboard computer for post-processing. An attitude and heading reference system (AHRS) is used to provide
the reference attitudes. The required angular rates and heading for this study are also given by the gyroscopes and compass
of the AHRS for the sake of system’s simplification. The Kalman filter is applied to estimate the helicopter’s accelerations
by using the GPS velocity measurements. The estimated accelerations form the fundamental elements of synthesizing the pseudo-roll
and the pseudo-pitch. With some legitimate simplifications and assumptions, the relation between the helicopter’s attitudes
and the accelerations estimated from the GPS velocity measurements can be developed. Furthermore, to enhance the accuracy
of the pseudo-attitudes, the angular rates acquired from the gyroscopes are incorporated into the estimation algorithm of
pseudo-attitudes by using a complementary filter.
相似文献
| Fei-Bin HsiaoEmail: |
10.
Dezhong Chen Shirong Ye Wei Zhou Yanyan Liu Peng Jiang Weiming Tang Bing Yuan Lewen Zhao 《GPS Solutions》2016,20(3):439-450
The difficulty to detect and repair cycle slip of carrier phase measurements is a key limit for continuously high accuracy of GNSS positioning and navigation services. We propose an automated cycle slip detection and repair method for data preprocessing of a CORS network. The method jointly uses double-differenced (DD) geometry-free (GF) combination and ionospheric-free observation corrected for the computed geometrical distance (IF-OMC) to estimate the cycle slips in dual-frequency observations. The DD GF combination, which is only affected by the ionospheric residual, can be used to detect cycle slips with high reliability except for special pairs such as (77, 60) on GPS L1/L2 frequencies. The detection principle of the IF-OMC observable is such that there is a large discontinuity related to the previous epoch when cycle slips occur at the present epoch. The disadvantages of these two combinations can be overcome employing the proposed detection method. The cycle slip pair (77, 60) has no effect on the GF combination, while a change of 14.65 m is derived from GPS L1/L2 observations using the IF-OMC algorithm. Using pre-determined station coordinates as precise values, we found that the accuracy of the DD IF-OMC combination was 18 mm for a 200-km CORS baseline. Therefore, cycle slips in dual-frequency observations can be correctly and uniquely determined using DD GF and IF-OMC equations. The proposed method was verified by adding simulated cycle slips in observations collected from the CORS network under a quiet ionosphere and shown to be effective. Moreover, the method was assessed with observations made during intense ionospheric activity, which generated extensive cycle slips. The results show that the algorithm can detect and repair all cycle slips apart from two exceptions relating to long data gaps. 相似文献
11.
The reliability of the classical geometry- and ionospheric-free (GIF) three-carrier ambiguity resolution (TCAR) degrades when applied to long baselines of hundreds of kilometers. To overcome this deficiency, we propose two new models, which are used sequentially to resolve wide-lane (WL) and narrow-lane (NL) ambiguities and form a stepwise ambiguity resolution (AR) strategy. In the first model, after a successful extra-wide-lane AR, the pseudorange and phase observations are combined to estimate WL ambiguities, in which the residual ionospheric delays and geometry effects are eliminated. In the second model, using the resolved ambiguities from the first step, the two WL ambiguities are combined to remove ionospheric and geometry effects. The unknown coefficients in the two models are determined in such that they minimize the formal errors in the ambiguity estimates to optimize the ambiguity estimation. Using experimental BeiDou triple-frequency observations, we evaluate our method and identify three advantages. First, the two models use double-differenced phase observations that are not differences across frequency. Second, the two models are entirely free from ionospheric delay and geometry effects. Third, the unknown estimates in the two models satisfy the minimum noise condition, which makes the formal errors in the float NL ambiguity estimates much lower than those obtained with common GIF TCAR methods, thereby directly and significantly increasing the success rate of AR compared to the cascaded integer resolution method and two other GIF combinations. 相似文献
12.
Pseudorange-based integrity monitoring, for example receiver autonomous integrity monitoring (RAIM), has been investigated
for many years and is used in various applications such as non-precision approach phase of flight. However, for high-accuracy
applications, carrier phase-based RAIM (CRAIM), an extension of pseudorange-based RAIM (PRAIM) must be used. Existing CRAIM
algorithms are a direct extension of PRAIM in which the carrier phase ambiguities are estimated together with the estimation
of the position solution. The main issues with the existing algorithms are reliability and robustness, which are dominated
by the correctness of the ambiguity resolution, ambiguity validation and error sources such as multipath, cycle slips and
noise correlation. This paper proposes a new carrier phase-based integrity monitoring algorithm for high-accuracy positioning,
using a Kalman filter. The ambiguities are estimated together with other states in the Kalman filter. The double differenced
pseudorange, widelane and carrier phase observations are used as measurements in the Kalman filter. This configuration makes
the positioning solution both robust and reliable. The integrity monitoring is based on a number of test statistics and error
propagation for the determination of the protection levels. The measurement noise and covariance matrices in the Kalman filter
are used to account for the correlation due to differencing of measurements and in the construction of the test statistics.
The coefficient used to project the test statistic to the position domain is derived and the synthesis of correlated noise
errors is used to determine the protection level. Results from four cases based on limited real data injected with simulated
cycle slips show that residual cycle slips have a negative impact on positioning accuracy and that the integrity monitoring
algorithm proposed can be effective in detecting and isolating such occurrences if their effects violate the integrity requirements.
The CRAIM algorithm proposed is suitable for use within Kalman filter-based integrated navigation systems.
相似文献
| Shaojun FengEmail: |
13.
In Global Navigation Satellite System (GNSS) positioning, the receiver measures the pseudorange with respect to each observable
navigation satellite and determines the position and clock bias. In addition to the GPS, several other navigation satellite
constellations including Glonass, Galileo and Compass can/will also be used to provide positioning, navigation, and timing
information. The paper is concerned with the solvability of the navigation problem when the receiver attempts to process measurements
from different constellations. As two different constellations may not be time-synchronized, the navigation problem involves
the determination of position of the receiver and clock bias with respect to each constellation. The paper describes an analytic
approach to account for the two-constellation navigation problem with three measurements from one constellation and two measurements
from another constellation. It is shown that the two-constellation GNSS navigation problem becomes the solving of a set of
two simultaneous quadratic equations or, equivalently, a quartic equation. Furthermore, the zero-crossover of the leading
coefficient and the sign of the discriminant of the quartic equation are shown to play a significant role in governing the
solvability, i.e., the existence and uniqueness of the navigation solutions.
相似文献
| Jyh-Ching JuangEmail: |
14.
准确固定非差模糊度是利用相位观测量获取高精度电离层延迟的关键。三频观测条件下常规的处理策略需依次固定超宽巷、宽巷以及窄巷模糊度,通常利用MW（melbourne-wubbena）组合解算宽巷模糊度时易受到码硬件延迟和观测噪声的影响而固定错误。利用北斗三频数据和GIM（grid ionosphenimap）产品,通过固定的超宽巷模糊度以及构造相位无几何组合解算宽巷模糊度,进而重构得到高精度电离层延迟,并且分离了码硬件延迟总量。结果表明,GIM模型辅助条件下宽巷模糊度固定成功率能达到100%,且消除了系统性偏差;电离层重构值与GIM模型改正值存在约1 m的差异,等效精度约6TECU;分离的码硬件延迟变化平稳,标准偏差不超过0.3 m。 相似文献
15.
Lambert Wanninger 《GPS Solutions》2009,13(2):133-139
Antenna changes at GNSS reference stations frequently produce discontinuities in the coordinate time series. These apparent
position shifts are mainly caused by changes of carrier-phase multipath effects and different errors in the antenna phase
center corrections. A monitoring method was developed and successfully tested, which requires additional GNSS observations
from a local, temporary reference station. Changes of carrier-phase measurement errors due to the antenna change are determined
and stored in L1 and L2 phase maps. These phase maps provide corrections to be applied either to the observation data obtained
before the antenna change or to the observation data obtained after the antenna change. The observation corrections are able
to remove coordinate discontinuities independent of the selected coordinate estimation algorithm.
相似文献
| Lambert WanningerEmail: |
16.
Total electron content processing from GPS observations to facilitate ionospheric modeling 总被引：2，自引：1，他引：1
With the increasing global distribution of high rate dual-frequency global positioning system (GPS) receivers, the production
of a real-time atmospheric constituent definition, total electron content (TEC), has become a beneficial contributor to the
modeling applications used in the assessment of GPS position accuracy and the composition of the ionosphere, plasmasphere,
and troposphere. Historically, TEC measurements have been obtained through post processing techniques to produce the quality
of data necessary for modeling applications with rigorous error estimate requirements. These procedures necessitated the collection
of large volumes of data to address the various abnormalities in the computation of TEC associated with the use of greater
data quality controls and source selection while real-time modeling environments must rely on autonomous controls and filtration
techniques to prevent the production of erroneous model results. In this paper we present methods for processing TEC in real
time, which utilize several procedures including the application of an ionospheric model to automatically perform quality
control on the TEC output and the computational techniques used to address receiver multipath, faulty receiver observations,
cycle-slips, segmented processing, and receiver calibrations. The resulting TEC measurements are provided with rigorous error
estimates validated using the vertical TEC from the Jason satellite mission.
相似文献
| Nelson A. BonitoEmail: |
17.
In this article, an algorithm for clock offset estimation of the GPS satellites is presented. The algorithm is based on a
Kalman-filter and processes undifferenced code and carrier-phase measurements of a global tracking network. The clock offset
and drift of the satellite clocks are estimated along with tracking station clock offsets, tropospheric zenith path delay
and carrier-phase ambiguities. The article provides a brief overview of already existing near-real-time and real-time clock
products. The filter algorithm and data processing scheme is presented. Finally, the accuracy of the orbit and clock product
is assessed with a precise orbit determination of the MetOp satellite and compared to results gained with other real-time
products.
相似文献
| André HauschildEmail: |
18.
Troposphere zenith path delays derived from the Global Data Assimilation System (GDAS) numerical weather model (NWM) are compared
with those of the International GNSS Service (IGS) solutions over a 1.5-year period at 18 globally distributed IGS stations.
Meteorological parameters can be interpolated from the NWM model at any location and at any time after December 2004. The
meteorological parameters extracted from the NWM model agree with in situ direct measurements at some IGS stations within
1 mbar for pressure, 3° for temperature and 13% for relative humidity. The hydrostatic and wet components of the zenith path
delay (ZPD) are computed using the meteorological parameters extracted from the NWM model. The total ZPDs derived from the
GDAS NWM agree with the IGS ZPD solutions at 3.0 cm RMS level with biases of up to 4.5 cm, which can be attributed to the
wet ZPDs estimates from the NWM model, considering the less accurate interpolated relative humidity parameter. Based on this
study, it is suggested that the availability and the precision of the GDAS NWM ZPD should be sufficient for nearly all GPS
navigation solutions.
相似文献
| Constantin-Octavian AndreiEmail: |
19.
Modeling spatial autocorrelation in spatial interaction data: empirical evidence from 2002 Germany journey-to-work flows 总被引：3，自引：3，他引：0
Daniel A. Griffith 《Journal of Geographical Systems》2009,11(2):117-140
Since before the inception of work by Okabe, the intermingling of spatial autocorrelation (i.e., local distance and configuration)
and distance decay (i.e., global distance) effects has been suspected in spatial interaction data. This convolution was first
treated conceptually because technology and methodology did not exist at the time to easily or fully address spatial autocorrelation
effects within spatial interaction model specifications. Today, however, sufficient computer power coupled with eigenfunction-based
spatial filtering offers a means for accommodating spatial autocorrelation effects within a spatial interaction model for
modest-sized problems. In keeping with Okabe’s more recent efforts to dissemination spatial analysis tools, this paper summarizes
how to implement the methodology utilized to analyze a particular empirical flows dataset.
相似文献
| Daniel A. GriffithEmail: |
20.
Artificial neural networks for predicting DGPS carrier phase and pseudorange correction 总被引：2，自引：2，他引：0
Arif Indriyatmoko Taesam Kang Young Jae Lee Gyu-In Jee Yong Beom Cho Jeongrae Kim 《GPS Solutions》2008,12(4):237-247
Artificial neural networks (ANNs) were used to predict the differential global positioning system (DGPS) pseudorange and carrier
phase correction information. Autoregressive moving average (ARMA) and autoregressive (AR) models were bounded with neural
networks to provide predictions of the correction. The neural network was employed to realize time-varying implementation.
Online training for real-time prediction of the carrier phase enhances the continuity of service of the differential correction
signals and, therefore, improves the positioning accuracy. When the correction signal from the DGPS was lost, the artificial
neural networks predicted the correction data with good accuracy for the navigation system during a limited period. Comparisons
of the prediction results using the two models are given.
相似文献
| Young Jae LeeEmail: |