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Precise estimation of residual tropospheric delays using a regional GPS network for real-time kinematic applications 总被引:7,自引:0,他引:7
A new method called Trop_NetAdjust is described to predict in real time the residual tropospheric delays on the GPS carrier
phase observables using the redundant measurements from a network of GPS reference stations. This method can not only enhance
the effectiveness and reliability of real-time kinematic users within the network, but also provide a valid approach to tropospheric
parameter variation forecasting. Trop_NetAdjust is theoretically based upon LS prediction criteria and enables the prediction
of residual tropospheric delays remaining after a standard model has been applied to the raw GPS measurements. Two cases are
analyzed, namely a first case when the delay is required for an existing satellite at a new point within the network and a
second case when the delay is required for a new satellite. Field tests were conducted using data collected in a network of
11 reference stations covering a 400×600 km region in southern Norway. The results were analyzed in the measurement domain
(ionospheric-free double-difference residuals) and showed improvements of 20 to 65% RMS errors using Trop_NetAdjust. The estimates
of the Trop_NetAdjust prediction accuracy were also obtained using the covariance analysis method. The agreement was consistently
better than 30% when compared with data from a real network.
Received: 28 February 2000 / Accepted: 9 January 2001 相似文献
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Navigation applications will benefit significantly from the improved reliability, availability, and accuracy offered by combining BeiDou Navigation Satellite System (BDS) and Global Positioning System (GPS). In the BDS/GPS navigation data fusion model, the effect of inter-system bias (ISB) must be considered. We present a detailed analysis of the pseudorange measurements for BDS and GPS and demonstrate the existence of code ISB in BDS/GPS measurements. The ISB mainly consists of the time system offset, the coordinate system difference, and the inter-system hardware delay bias. A method based on statistical hypothesis testing is proposed to assess the stability and difference of the BDS–GPS ISB. Real data from 18 stations equipped with six types of receivers are used to compute the ISB. The results illustrate that (a) receiver-dependent ISBs are evident and comparatively consistent, with the maximum ISB observed in our experiments being ?1516 ns, (b) these receiver-dependent ISBs exhibit great stability in terms of their standard deviation and intra-day variation, and (c) the estimated ISBs for each BDS satellite type with respect to GPS are consistent. 相似文献
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Modernized GPS and Galileo will provide triple-frequency signals for civil use, generating a high interest to examine the improvement of positioning performance using the triple-frequency signals from both constellations over baselines up to hundreds or thousands of kilometers. This study adopts a generalized GPS/Galileo long-range approach to process the mutually compatible GPS and Galileo triple-frequency measurements for high-precision long baseline determination. The generalized approach has the flexibility to deal with GPS and Galileo constellations separately or jointly, and also the capability to handle dual or triple-frequency measurements. We compared the generalized long-range approach with the Bernese v5.0 software on two test baselines located in East Asia and obtained highly compatible computational results. Further, in order to assess possible improvement of GPS/Galileo long baseline determination compared with the current dual-frequency (L1/L2) GPS, we simulated GPS and Galileo measurements of the test baselines. It is shown that the current level of accuracy of daily baseline solutions can be improved by using the additional Galileo constellation. Both the additional constellation and the triple-frequency measurements can improve ambiguity resolution performance, but single-constellation triple-frequency ambiguity resolution is more resistant to the influences of code noise and multipath than dual-constellation dual-frequency ambiguity resolution. Therefore, in environments where large code noise or multipath is present, the use of triple-frequency measurements is the main factor for improving ambiguity resolution performance. 相似文献
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Classifying Human Activity Patterns from Smartphone Collected GPS data: A Fuzzy Classification and Aggregation Approach 下载免费PDF全文
Smartphones have emerged as a promising type of equipment for monitoring human activities in environmental health studies. However, degraded location accuracy and inconsistency of smartphone‐measured GPS data have limited its effectiveness for classifying human activity patterns. This study proposes a fuzzy classification scheme for differentiating human activity patterns from smartphone‐collected GPS data. Specifically, a fuzzy logic reasoning was adopted to overcome the influence of location uncertainty by estimating the probability of different activity types for single GPS points. Based on that approach, a segment aggregation method was developed to infer activity patterns, while adjusting for uncertainties of point attributes. Validations of the proposed methods were carried out based on a convenient sample of three subjects with different types of smartphones. The results indicate desirable accuracy (e.g. up to 96% in activity identification) using of this method. Two examples are provided in the Appendix to illustrate how the proposed methods could be applied in environmental health studies. Researchers could tailor this scheme to fit a variety of research topics. 相似文献
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Differential carrier phase observations from GPS (Global Positioning System) integrated with high-rate sensor measurements,
such as those from an inertial navigation system (INS) or an inertial measurement unit (IMU), in a tightly coupled approach
can guarantee continuous and precise geo-location information by bridging short outages in GPS and providing a solution even
when less than four satellites are visible. However, to be efficient, the integration requires precise knowledge of the lever
arm, i.e. the position vector of the GPS antenna relative to the IMU. A previously determined lever arm by direct measurement
is not always available in real applications; therefore, an efficient automatic estimation method can be very useful. We propose
a new hybrid derivative-free extended Kalman filter for the estimation of the unknown lever arm in tightly coupled GPS/INS
integration. The new approach takes advantage of both the linear time propagation of the Kalman filter and the nonlinear measurement
propagation of the derivative-free extended Kalman filter. Compared to the unscented Kalman filter, which in recent years
is typically used as a superior alternative to the extended Kalman filter for nonlinear estimation, the virtue of the new
Kalman filter is equal estimation accuracy at a significantly reduced computational burden. The performance of the new lever
arm estimation method is assessed with simulated and real data. Simulations show that the proposed technique can estimate
the unknown lever arm correctly provided that maneuvers with attitude changes are performed during initialization. Field test
results confirm the effectiveness of the new method. 相似文献
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The Global Positioning System (GPS), in addition to providing precise navigation and positioning information, produces precise
time and frequency measurements. These measurements result from the atomic clocks in the GPS satellites, which are closely
coupled to Universal Coordinated Time as maintained by the U. S. Naval Observatory [UTC(USNO)]. The application of these measurements
to timekeeping and other systems requiring precise time and frequency is distinct from the navigation/positioning mission.
This article will describe the differences in application of GPS to time and frequency uses. These uses will be described
in the major areas of timekeeping; stationary uses, such as communications networking; and mobile use for aircraft and shipboard
applications. The major considerations in application and operation with precise and less-capable oscilators will be described.
Examples and data will be presented to illustrate the applications. ? 1999 John Wiley & Sons, Inc. 相似文献
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Stochastic assessment of GPS carrier phase measurements for precise static relative positioning 总被引:17,自引:11,他引:17
Global positioning system (GPS) carrier phase measurements are used in all precise static relative positioning applications.
The GPS carrier phase measurements are generally processed using the least-squares method, for which both functional and stochastic
models need to be carefully defined. Whilst the functional model for precise GPS positioning is well documented in the literature,
realistic stochastic modelling for the GPS carrier phase measurements is still both a controversial topic and a difficult
task to accomplish in practice. The common practice of assuming that the raw GPS measurements are statistically independent
in space and time, and have the same accuracy, is certainly not realistic. Any mis-specification in the stochastic model will
inevitably lead to unreliable positioning results. A stochastic assessment procedure has been developed to take into account
the heteroscedastic, space- and time-correlated error structure of the GPS measurements. Test results indicate that the reliability
of the estimated positioning results is improved by applying the developed stochastic assessment procedure. In addition, the
quality of ambiguity resolution can be more realistically evaluated.
Received: 13 February 2001 / Accepted: 3 September 2001 相似文献
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Geometry-free undifferenced, single and double differenced analysis of single frequency GPS, EGNOS and GIOVE-A/B measurements 总被引:3,自引:1,他引:2
This paper demonstrates a geometry-free GNSS measurement analysis approach and presents results of single frequency GPS, EGNOS
and GIOVE short and zero baseline measurements. The purpose is to separate the different contributions to the measurement
noise of pseudo range code and carrier phase observations at the receiver. The influence of multipath on the different combinations
of observations is also determined. Quantitative results are presented for the thermal code and phase measurement noise and
for the correlation between the observations. Comparison of the results with theoretical approximations confirms the validity
of the used approach. Results from field measurements clearly show less thermal noise on the Galileo E1BC observations than
on the GPS L1C/A observations due to the new signal modulation. The feasibility of ambiguity resolution with a geometry-free
model is also discussed including the significant impact of multipath thereon. 相似文献
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Michael Moore Christopher Watson Matt King Simon McClusky Paul Tregoning 《Journal of Geodesy》2014,88(9):887-900
Continuous global positioning system (GPS) stations propagate biases and spurious signals into the derived parameter time series when the measurements are subject to site-specific effects, such as multipath. This is a particular problem in the investigation of geophysical and atmospheric phenomena where signals may be small in magnitude. A methodology to remove these erroneous signals from long-term time series will significantly increase the usefulness of the derived time series. This work provides the theoretical basis for use of an empirical site model (ESM) derived from post-fit phase residuals to mitigate unmodelled site-specific errors. Additionally, we also investigate the effectiveness of applying an ESM to a regional GPS network and a short baseline solution. Under most observing scenarios, we show that the ESM approach is predicted to improve the precision and accuracy of the site coordinates. However, it is important to note that we found some scenarios where the ESM can introduce a bias. For instance, when the antenna is mounted close to the ground. In this scenario, for a short baseline, we observed the introduction of a 4-mm bias in height. Use of an ESM for the same short baseline with an uncalibrated radome substantially improves the results by removing a large bias of over 10 mm in height. Similarly, application of an ESM derived from historic data yields similar improvements. This demonstrates that the ESM can be a powerful tool when applied to appropriate site-specific configurations and could potentially be implemented in routine GPS analysis for a broad range of applications. 相似文献
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Modern dual-frequency global positioning system (GPS) receivers are capable of providing direct measurements of both L1 C/A (C1) and P code (P1) without the use of the Y-codes under Anti-Spoofing. A discrepancy or bias between the C1 and P1 measurements from these receivers has however been of concern to operators and users of GPS reference networks. For the
purpose of modeling and estimation, the nature and characteristics of the discrepancy must be investigated. The research results
presented indicate that the discrepancy between the C1 and P1 measurements contains two different types of components: one is of constant type while another is time variant. A method
has been developed for their modeling and estimation. The residual C1–P1 time series after a satellite-dependent bias removal agree at a few-centimeter level, indicating the effectiveness of the
proposed model. This allows the C1–P1 discrepancy, both constant and non-constant components, to be removed from GPS reference network solutions. Numerical results
are provided to support the analysis.
Received: 12 October 1999 / Accepted: 11 May 2000 相似文献
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Satellite clock bias estimation for iGPS 总被引:4,自引:0,他引:4
John Pratt Penina Axelrad Kristine M. Larson Bruno Lesage Richard Gerren Nicholas DiOrio 《GPS Solutions》2013,17(3):381-389
The High Integrity GPS program seeks to provide enhanced navigation performance by combining conventional GPS with a communications and ranging broadcast from the Iridium® Communications System. Through clock and message aiding, it would enable existing GPS receivers to acquire and track in more challenging environments. As is the case for standard GPS, accurate and precise timing is key to performance. An approach is presented for estimating the bias of each Iridium satellite clock using satellite-to-ground and satellite-to-satellite measurements. The satellite clock bias estimates are based on a Kalman filter that incorporates code-type observations from the measurements at 10 s intervals. Filter parameters are set based on the expected behavior of the clocks, allowing for discontinuous bias and frequency adjustments due to ground commands. Typical results show the current filter to be accurate to within 200 ns while always meeting the initial system specification of half a microsecond. 相似文献
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北斗导航卫星系统测距信号的精度分析 总被引:1,自引:0,他引:1
基于单测站和短基线实验的伪距相位差值 (Code-minus-phase Combination, CC)和多路径(Multipath, MP)两类组合观测值,对比分析了北斗(BD)和GPS测距信号质量,并检验了多路径误差对CC模糊度固定的影响。结果表明:BD GEO卫星(Geostationary Earth Orbit)的测距信号质量优于IGSO卫星(Inclined Geosynchronous Satellite Orbit),且两类测距信号的多路径误差分别包含长、短期的变化趋势。针对CC模糊度固定,当采用较长时间段(如本文中的600s)时,GPS L1/L2和BD B1/B2四个频段上的成功率均超90%;而对于快速模糊度固定(如仅采用120秒),由于受强多路径误差影响,BD IGSO卫星的固定成功率最低,不超过50%。 相似文献
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The density of GPS measurements is usually one of the key issues in resolving 3-D coseismic deformation field from integrating GPS and Interferometric Synthetic Aperture Radar (InSAR) measurements with pure mathematic interpolation methods An approach that combines the elastic dislocation model with the Best Quadratic Unbiased Estimator (BQUE) or a robust estimation method named IGG (Institute of Geodesy and Geophysics) is proposed to reconstruct 3-D coseismic deformation field, in which only a small amount of GPS data is needed to produce a reasonable initial 3-D coseismic deformation. Then the BQUE and IGG are used to weight the InSAR and GPS measurements to avoid computational issues caused by the negative variance problem and to decrease the impact from gross errors. The Wenchuan earthquake is used to test the proposed method. We find that the developed method makes it possible to use only a few GPSs and InSAR data to recover the 3-D coseismic deformation field, which offers extensive future usage for measuring earthquake deformation, particularly in some tectonically active regions with sparse GPS measurements. 相似文献
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The accuracy of standalone GPS positioning improved significantly when Selective Availability was turned off in May 2000. With the availability of various public GPS related products including precise satellite orbits and clocks, and ionosphere maps, a single-frequency standalone user can experience even a further improvement of the position accuracy. Next, using carrier phase measurements becomes crucial to smoothen the pseudorange noise. In this contribution, the most critical sources of error in single-frequency standalone positioning will be reviewed and different approaches to mitigate the errors will be considered. An optimal filter (using also carrier phase measurements) will be deployed. The final approach will then be evaluated in a decently long static test with receivers located in different regions of the world. Kinematic experiments have also been performed in various scenarios including a highly dynamic flight trial. The accuracy, in general, can be confirmed at 0.5 m horizontal and 1 m vertical, with static tests. Ultimate results demonstrate an accuracy close to 2 dm (95%) for the horizontal position components and 5 dm (95%) for the vertical in the flight experiment.
相似文献
Anh Quan LeEmail: |
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Dah-Jing Jwo 《GPS Solutions》2004,8(3):160-169
The solution for the receivers position and clock bias using four or more GPS pseudorange measurements involves nonlinear quadratic equations. One of the popular techniques for linearizing the equations and solving them is the least squares (LS) scheme based on an iterative gradient approach. For real-time applications when the solution is to be obtained within a time of the order of 100 ns, a computer often cannot comply with the desired computation time, or high-end computers are too expensive. In this paper various ordinary differential equation formulation schemes, and corresponding circuits of neuron-like analog processors, will be described and several tested in order to ascertain their suitability for GPS navigation processing purposes. The circuits of simple neuron-like analog processors are employed essentially for on-line inversion of matrices, which is usually required for determining LS solutions, as well as dilution of precision (DOP) calculation in standard GPS receivers. Data from single epoch and kinematic positioning experiments will be simulated to validate the effectiveness of the proposed scheme. The properties and performance of the proposed scheme will be assessed and compared to those of the conventional method of matrix inversion. 相似文献
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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
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GPS观测数据中的仪器偏差对确定电离层延迟的影响及处理方法 总被引:48,自引:5,他引:43
本文通过设计不同的计算方案详细分析了GPS观测中的仪器偏差对确定电离层延迟的影响,利用多天实测数据,结合仪器偏差与电离层延迟的分离方法,探讨了仪器偏差的稳定性,并提出了一种静态确定电离层延迟的方案。算例表明它能有效克服仪器偏差影响。 相似文献