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1.
Jin Xinxiang 《地球空间信息科学学报》2013,16(2):65-73
The DGPS technique can provide considerably better relative positioning accuracy than the stand-alone GPS positioning, but the improvement depends on the distance between the user and the reference station (spatial correlation), the latency of differential corrections (temporal correlation), and the quality of differential corrections. Therefore, how to correctly generate differential corrections as well as their pricision is very important to the DGPS positioning technique. This paper presents a new algorithm for generating differential GPS corrections. This algorithm directly uses code and carrier observations in the measurement model of a Kalman filter, so that it is possible to use a simple stochastic model and to use the standard algorithm of the Kalman filter. The algorithm accounts for biases like multipath errors and instrumental delays in code observations and it shows how differential corrections are differently affected by code biases when dual or single frequency data is used. In addition, the algorithm can be integrated with a real time quality control procedure. As a result, the quality of differential corrections can be guaranteed with a certain probability. 相似文献
2.
Xin-Xiang Jin 《Journal of Geodesy》1996,70(11):673-680
This paper presents a new algorithm for generating differential GPS corrections. This algorithm directly uses code and carrier observations in the measurement model of a Kalman filter, so that it is possible to use a simple stochastic observation model and to use the standard algorithm of the Kalman filter. The algorithm accounts for biases like multipath errors and instrumental delays in code observations and it shows how differential corrections are differently affected by code biases when dual or single frequency data are used. 相似文献
3.
X. X. Jin 《Journal of Geodesy》1997,71(7):411-422
This paper derives a DGPS positioning algorithm, referred to as the algorithm for carrier-adjusted DGPS positioning. This
algorithm can be applied by a DGPS user when code and carrier observations are available and when the dynamic behaviours of
both mobile positions and receiver-clock biases can and cannot be modelled. Since the algorithm directly uses code and carrier
observations, the stochastic model of observations has a simple structure and can be easily specified. When the dynamic behaviour
of mobile positions can be modelled, the algorithm can provide recursive solutions of the positions, on the other hand, when
the behaviour cannot be modelled, it can provide their instantaneous solutions. Furthermore, the algorithm can integrate with
a real-time quality-control procedure so that the quality of the position estimates can be guaranteed with a certain probability.
Since in the use of the algorithm there always exist redundant observations unless the position parameters are inestimable,
the quality control can even be performed when only four satellites are tracked. Using the algorithm and real GPS data collected
at a 100-km baseline, this contribution investigates how DGPS positioning accuracies vary with the type of observables used
at reference and mobile stations, and how important it is to choose an elevation-dependent standard deviation for code observations
in DGPS data reduction. It was found that using carrier observations along with code observations is more important at the
reference station than at the mobile station. Choosing an elevation-dependent standard deviation for code observations can
result in better positioning accuracy than choosing a constant standard deviation for code observations. For the 100-km baseline,
half-metre single-epoch positioning accuracy was achieved when dual-frequency data was used at both reference and mobile stations.
The positioning accuracy became better than 0.75m when the types of observable used at the mobile station were replaced by
L1 code and carrier.
Received: 9 April 1996 / Accepted: 6 February 1997 相似文献
4.
M. R. Mosavi 《GPS Solutions》2006,10(2):97-107
Position information obtained from standard global positioning system (GPS) receivers has time variant errors. For effective use of GPS information in a navigation system, it is essential to model these errors. A new approach is presented for improving positioning accuracy using neural network (NN), fuzzy neural network (FNN), and Kalman filter (KF). These methods predict the position components’ errors that are used as differential GPS (DGPS) corrections in real-time positioning. Method validity is verified with experimental data from an actual data collection, before and after selective availability (SA) error. The result is a highly effective estimation technique for accurate positioning, so that positioning accuracy is drastically improved to less than 0.40 m, independent of SA error. The experimental test results with real data emphasize that the total performance of NN is better than FNN and KF considering the trade-off between accuracy and speed for DGPS corrections prediction. 相似文献
5.
6.
GPS code pseudorange measurements exhibit group delay variations at the transmitting and the receiving antenna. We calibrated C1 and P2 delay variations with respect to dual-frequency carrier phase observations and obtained nadir-dependent corrections for 32 satellites of the GPS constellation in early 2015 as well as elevation-dependent corrections for 13 receiving antenna models. The combined delay variations reach up to 1.0 m (3.3 ns) in the ionosphere-free linear combination for specific pairs of satellite and receiving antennas. Applying these corrections to the code measurements improves code/carrier single-frequency precise point positioning, ambiguity fixing based on the Melbourne–Wübbena linear combination, and determination of ionospheric total electron content. It also affects fractional cycle biases and differential code biases. 相似文献
7.
基于GPS双频原始观测值的精密单点定位算法及应用 总被引:9,自引:2,他引:7
本文提出一种基于GPS双频原始观测值的PPP算法,与基于消电离层组合观测值的传统PPP算法不同,新算法通过参数化站星视线方向的电离层延迟以消除其对PPP估值的不利影响;该新算法可以有效避免观测值组合过程所引起的观测数据噪声以及多路径效应被放大的不利影响;同时在利用扩展卡尔曼滤波模型进行未知参数的递归估计过程中,通过对大气延迟参数引入符合实际的约束,可以加快滤波收敛,提高参数估值的可靠性;视线方向电离层延迟可与其他未知参数同时估计得到,进而便于利用PPP技术进行精密电离层研究;此外,对于可能的模型误差(如码观测值粗差、相位观测值周跳等),基于DIA的质量控制策略以消除或削弱其对参数估值的不利影响。利用实测数据对新算法在静态、低动态以及高动态定位应用方面的精度进行检验,结果表明,静、动态定位结果的外符合精度可分别达到1~2 cm和7~8 cm,验证了新算法的可行性和有效性。 相似文献
8.
基于方差分量估计原理的自适应卡尔曼滤波及其应用 总被引:9,自引:0,他引:9
简单介绍了GPS伪距动态定位的卡尔曼滤波模型的建立,针对传统卡尔曼滤波中动态噪声不准或不容易确定以及因动态目标机动而导致滤波发散的现象,提出了一种根据方差分量估计原理,利用预报残差计算模型的动态噪声方差分量的自适应滤波算法,当利用预报残差进行计算时,这一方面增加的计算量不大,能有效地克服由上述原因而导致的滤波不稳定现象,适用于GPS动态定位数据的实时处理。 相似文献
9.
A user of heterogeneous GPS and GLONASS receiver pairs in differential positioning mode will experience ambiguity fixing challenges due to the presence of inter-channel biases. These biases cannot be canceled by differencing GLONASS observations, whether pseudorange or carrier phase. Fortunately, pre-calibration of GLONASS pseudorange and carrier phase observations can make ambiguity fixing for GPS/GLONASS positioning much easier. We propose an effective algorithm that transforms an RTK (real-time kinematic) solution in a mixed receiver baseline from a float to a fixed ambiguity solution. Carrier phase and code inter-channel biases are estimated from a zero baseline. Then, GLONASS both carrier phase and code observations are corrected accordingly. The results show that a mixed baseline can be transformed from a float (~100 %) to a fixed (more than 92 %) solution. 相似文献
10.
11.
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
12.
David M. Gleason 《Journal of Geodesy》1996,70(5):263-275
A current pursuit of the geodetic community is the optimal integration of differential GPS (DGPS) and inertial navigation system (INS) data streams for precise and efficient position and gravity vector surveying. Therein a complete INS and multiple-antenna GPS receiver payload, mounted on a moving platform, is used in conjunction with a network of ground-fixed single antenna GPS receivers. This paper presents a complete, GPS-based, external updating measurement model for the applicable Kalman filter. The model utilizes four external observation types for every GPS satellite in-view: DGPS range differences, single phase differences, and single phase-rate differences; as well as the mobile, multipleantenna GPS receiver's measurement of theerrors in the INS's estimate of the phase difference between any two vehicle-borne GPS antennae. Although not widely conveyed in the geodetic world, the inertial navigation community has long known that traditional Kalman filter covariance propagation recurrences are inherently unstable when such highly accurate external updates are repeatedly applied (every 1 second) over long time durations. A hybrid square root covariance/U — D covariance factorization approach is a numerically stable alternative and is reviewed herein. The hybrid makeup of the algorithm is necessitated by the correlated nature of the fourth type of GPS external measurement listed above (each vehicle-borne GPS antenna formstwo baselines). Such measurement correlations require a functional transformation of the overall external updating model to permit the multiple updates (simultaneously available at each updating epoch) to be sequentially (and efficiently) processed. An appropriate transformation is given. Stable covariance propagation relationships are presented and the transformed Kalman gain is also furnished and its use in the determination of the externally updated error states is discussed. Specific DGPS/INS instabilities produced by the traditional recurrences are displayed. The stable alternative method requires about 25% more CPU time than the traditional Kalman recurrences. With the ever-increasing computational speeds of microprocessors, this added CPU time is of no real concern. 相似文献
13.
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
14.
Triple Differencing with Kalman Filtering: Making It Work 总被引:4,自引:0,他引:4
Since global positioning system (GPS) measurements are ranges (code) and biased ranges (carrier), it seems natural to model
them as ranges and determine the biases. This is particularly compelling since the double-difference range biases turn out
to be integers. At some level there is also an elegance, perhaps therefore a naturalness, to modeling the carrier measurements
as time differences of double differences. While something is lost something else is gained. Here we apply the proven delayed-state
Kalman filter to processing carrier phase measurements as triple differences. In practice we process these triple differences
along with double-difference code measurements. We also treat the measurement error as, mostly, Gauss-Markov states to be
determined. Many of the details are discussed and experimental results are included. These demonstrate that excellent performance
can be obtained if the Kalman filter modeling is done carefully. ? 2000 John Wiley & Sons, Inc. 相似文献
15.
16.
Assessment of the LandStar Real-Time DGPS Service under Several Operational Conditions 总被引:1,自引:0,他引:1
LandStar is a differential global positioning service (DGPS) that provides 24-h real-time positioning for various applications
on land, water, and air in North America, Australia, New Zealand, Europe, and Africa. Its focus is on real-time applications
requiring a submeter positioning capability such as agriculture, forestry, Geospatial Information Systems (GIS), survey/mapping,
and land/vehicular navigation. LandStar uses a Wide Area Network of reference stations to derive DGPS corrections to model
the variation of GPS error sources over a large area. These model parameters are used by the Virtual Reference Station processors
to calculate standard corrections that are available for all predefined locations in the network. The corrections are transmitted
to the user by L-band satellite communication in the standard RTCM SC104 DGPS correction format. This article investigates
the performance of the LandStar Mk III system under various operational conditions and assesses its performance in both static
and kinematic modes. Four field tests were conducted during 12 months that tested the sysem in clear static and kinematic
conditions as well as suboptimal environments associated with low and heavy foliage conditions. Both the accuracy and availability
of the system under these conditions is investigated, with an emphasis on whether the above variables are caused by the LandStar
system differential corrections, the GPS measurements, or a combination of both. ? 1999 John Wiley & Sons, Inc. 相似文献
17.
18.
SiGOG: simulated GPS observation generator 总被引:3,自引:0,他引:3
19.
In recent years the importance of real-time positioning and navigation with the Global Positioning System (GPS) has grown
rapidly. Starting from the establishment of differential GPS (DGPS) reference stations for marine and land navigation, new
users and applications have emerged that resulted in a high demand for the establishment of a high-density network of reference
stations around the world. Many countries have established their own DGPS service, which is either governmentally or commercially
owned. These services are referred to as Local Area DGPS Systems (LADGPS). However, the costs for the establishment and maintenance
of a dense network of reference stations are very high. Therefore Wide Area DGPS Systems (WADGPS) are being developed to overcome
the main drawbacks of LADGPS. In this case, only a few reference stations are used to cover a large area, such s a continent
like Europe. To achieve high positioning accuracies, real-time modeling of the main error sources for long-range baselines
is required as errors in the satellite orbit and ionospheric refraction do not cancel entirely in double differencing. In
this article, a real-time correction model based on the Kalman filter for WADGPS and networked LADGPS services is discussed
and results of field tests in a WADGPS network in Europe are presented. ? 2000 John Wiley & Sons, Inc. 相似文献