共查询到20条相似文献,搜索用时 0 毫秒
1.
U. Fernández-Plazaola T. M. Martín-Guerrero J. T. Entrambasaguas 《Journal of Geodesy》2008,82(4-5):269-278
A new method for resolving the carrier-phase integer ambiguity in Global Navigation Satellite Systems (GNSS) is presented:
the MOdified Cholesky factorization for Ambiguity (MOCA) resolution. The characteristics and features of this method are described
and results obtained using a software simulator and an emulator are presented to validate its efficiency. The results are
then compared to those obtained using another existing method and good performance of the MOCA method in new GNSS systems
is shown. Furthermore, the proposed method yields accurate results even when short time spans are used or when there are poor
estimations of measurement error, making it immune to non-ideal conditions and ultimately a practical solution for real applications. 相似文献
2.
U. Fernández-Plazaola T. M. Martín-Guerrero J. T. Entrambasaguas-Muñoz M. Martín-Neira 《Journal of Geodesy》2004,78(1-2):96-102
The Null method is a technique to fix the ambiguity in L1 phase measurements of the global positioning system (GPS). The method is adapted to new global navigation satellite systems (GNSS) which offer phase measurements at three frequencies. In order to validate the efficiency of the adapted method, results obtained using a software simulator and an emulator are presented. The results are then compared to those obtained with the least-squares ambiguity decorrelation adjustment (LAMBDA) method. Good performance of the Null method in new GNSS systems is shown.Acknowledgments. The measurements used were provided by the European Space Agency, and were generated by Spectra Precision Terrasat under contract No. 12.406/77/NL/DS. The authors thank Maria Belmontes Rivas for her comments and the reviewers for their suggestions. 相似文献
3.
GLONASS frequency division multiple access signals render ambiguity resolution (AR) rather difficult because: (1) Different wavelengths are used by different satellites, and (2) pseudorange inter-frequency biases (IFBs) cannot be precisely modeled by means of a simple function. In this study, an AR approach based on the ionospheric-free combination with a wavelength of about 5.3 cm is assessed for GLONASS precise point positioning (PPP). This approach simplifies GLONASS AR because pseudorange IFBs do not matter, and PPP-AR can be enabled across inhomogeneous receivers. One month of GLONASS data from 165 European stations were processed for different network size and different durations of observation periods. We find that 89.9% of the fractional parts of ionospheric-free ambiguities agree well within ± 0.15 cycles for a small network (radius = 500 km), while 77.6% for a large network (radius = 2000 km). In case of the 3-hourly GLONASS-only static PPP solutions for the small network, reliable AR can be achieved where the number of fixed GLONASS ambiguities account for 97.6% within all candidate ambiguities. Meanwhile, the RMS of the east, north and up components with respect to daily solutions is improved from 1.0, 0.6, 1.2 cm to 0.4, 0.4, 1.1 cm, respectively. When GPS PPP-AR is carried out simultaneously, the positioning performance can be improved significantly such that the GLONASS ambiguity fixing rate rises from 74.4 to 95.4% in case of hourly solutions. Finally, we introduce ambiguity-fixed GLONASS orbits to re-attempt GLONASS PPP-AR in contrast to the above solutions with ambiguity-float orbits. We find that ambiguity-fixed orbits lead to clearly better agreement among ionospheric-free ambiguity fractional parts in case of the large network, that is 80.5% of fractional parts fall in ± 0.15 cycles in contrast to 74.6% for the ambiguity-float orbits. We conclude that highly efficient GLONASS ionospheric-free PPP-AR is achievable in case of a few hours of data when GPS PPP-AR is also accomplished, and ambiguity-fixed GLONASS orbits will contribute significantly to PPP-AR over wide areas. 相似文献
4.
Qile Zhao Zhiqiang Dai Zhigang Hu Binzi Sun Chuang Shi Jingnan Liu 《GPS Solutions》2015,19(4):589-599
5.
针对BDS单系统未校准相位延迟(UPD)估计以及不同时长精密单点定位(PPP)模糊度固定对定位精度影响的问题,该文选取56个测站估计UPD,利用未参与UPD计算的8个测站进行不同时长BDS静态PPP模糊度固定实验。结果表明:BDS星间单差宽巷和窄巷UPD在连续时段内具有一定的稳定性,其估计精度满足用于PPP模糊度固定要求。时长越短模糊度固定率越低。以IGS周解为参考值,不同时长模糊度固定解较浮点解三维定位精度均提高12%以上,时长越短模糊度固定解精度提高越显著。因此,模糊度固定是提高BDSPPP定位精度的重要手段。 相似文献
6.
GPS Solutions - Frequency diversity is expected to benefit the ambiguity resolution (AR) with the modernization of global navigation satellite system. As one classic AR method, triple-carrier AR... 相似文献
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8.
A discrimination test procedure for ambiguity resolution on-the-fly 总被引:16,自引:2,他引:16
Ambiguity validation tests include the acceptance test and discrimination test, which are both important steps in the Global
Positioning System ambiguity resolution process. An ambiguity discrimination test procedure based on a test statistic which
is constructed by the difference (not the ratio as used in current procedures) between the minimum and second minimum quadratic
form of the residuals in ambiguity identification, and its standard deviation, is proposed. The distribution function of the
proposed test statistic is theoretically identified as a standard normal distribution when the known a priori variance factor
is used, or as a Student's t distribution when the estimated variance factor is used. With this procedure, the ambiguity discrimination test is based
on a more rigorous test statistic whose critical value can be calculated with any chosen level of significance. Test results
indicate that the proposed ambiguity discrimination test procedure is reliable for use in ambiguity resolution on-the-fly.
Received: 17 December 1997 / Accepted: 30 June 1998 相似文献
9.
Luc Fraiture 《GPS Solutions》2003,6(4):219-228
A new approach for ambiguity resolution is presented and tested by means of Monte-Carlo simulations. This approach applies
to both single and double phase differences sampled at a given instant, and to any number of baselines and lines of sight,
provided the number of lines of sight exceeds a certain threshold. The algorithms are based on the combined global geometry
of the baselines and lines of sight and thereby consider all geometric constraints that are inherent in the problem. The algorithms
have been programmed and applied to a large number of different configurations of GPS sight lines, and limited to baselines
of approximately 1 m in length and the GPS L1 frequency only. The cause of the occurrence of multiple solutions has been investigated.
To check the adequacy and limitations of the new algorithms for practical application, it was assessed in which proportion
the algorithms either failed to provide a result, provided a false result, or provided a good result as a function of number
of baselines, lines of sight and accuracy of the ambiguous phase difference measurements.
Electronic Publication 相似文献
10.
传统网络RTK模糊度解算方法需要多个历元的观测数据,并且要进行周跳的探测和修复,影响模糊度解算的效率。本文提出一种单历元确定网络RTK双差整周模糊度的新方法。首先利用测码伪距观测值和载波相位观测值的单历元数据组成双差联合观测方程,采用改进LABMDA算法进行两步搜索确定GPS双差相位观测值的宽巷模糊度。确定宽巷模糊度后,再用宽巷模糊度值和载波相位观测值组成新的联合观测方程,大大改善了方程的状态,可以准确解算出GPS双差整周模糊度,显著提高了网络RTK整周模糊度固定的效率。 相似文献
11.
12.
Rapid GPS ambiguity resolution for short and long baselines 总被引:3,自引:0,他引:3
A method of quick initial carrier cycle ambiguity resolution is described. The method applies to high-quality dual-band global
positioning system observations. Code measurements on both frequencies must be available. The rapidity of the method is achieved
through smoothing pseudoranges by phase observables and forming linear combinations between the phase observables. Two cases
are investigated. Case 1: ionospheric bias is neglected (short distances); and case 2: the bias is taken into account (longer
distances, more than, say, 10 km). The method was tested on six baselines, from 1 to 31 km long. In most cases, single-epoch
ambiguity resolution was achieved.
Received: 6 October 1999 / Accepted: 4 March 2002 相似文献
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14.
The ratio test for future GNSS ambiguity resolution 总被引:5,自引:5,他引:5
The performance of the popular ambiguity ratio test is analyzed. Based on experimental and simulated data, it is demonstrated that the current usage of the ratio test with fixed critical value is not sustainable in light of the enhanced variability that future global navigation satellite system (GNSS) ambiguity resolution will bring. As its replacement, the model-driven ratio test with fixed failure rate is proposed. The characteristics of this fixed-failure rate ratio test are described, and a performance analysis is given. The relation between its critical value and various GNSS model parameters is also studied. Finally, a procedure is presented for the creation of fixed failure rate look-up tables for the critical values of the ratio test. 相似文献
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16.
A comparison of three PPP integer ambiguity resolution methods 总被引:2,自引:5,他引:2
Precise point positioning (PPP) integer ambiguity resolution with a single receiver can be achieved using advanced satellite augmentation corrections. Several PPP integer ambiguity resolution methods have been developed, which include the decoupled clock model, the single-difference between-satellites model, and the integer phase clock model. Although similar positioning performances have been demonstrated, very few efforts have been made to explore the relationship between those methods. Our aim is to compare the three PPP integer ambiguity resolution methods for their equivalence. First, several assumptions made in previous publications are clarified. A comprehensive comparison is then conducted using three criteria: the integer property recovery, the system redundancy, and the necessary corrections through which the equivalence of these three PPP integer ambiguity resolution methods in the user solution is obtained. 相似文献
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18.
Weiming Tang Wenjian Liu Xuan Zou Zongnan Li Liang Chen Chenlong Deng Chuang Shi 《Journal of Geodesy》2016,90(12):1359-1369
19.
Triple-frequency carrier ambiguity resolution for Beidou navigation satellite system 总被引:3,自引:3,他引:3
The Chinese Beidou system, also known as Compass, has entered its trial operational stage and can already provide services for triple-frequency users. Using triple-frequency signals is expected to be of great benefit for ambiguity resolution. Based on error characteristic analysis of the Beidou frequencies, we introduce the procedure of selecting the best combinations of triple-frequency signals. The geometry-based model and geometry-free model of triple-frequency signals are presented. Three triple-frequency carrier ambiguity resolution (TCAR) methods are described, which include the cascading rounding method, the stepwise AR method and the modified stepwise AR method. In order to evaluate the performance of these methods, observations from baselines of various lengths were collected using Beidou triple-frequency receivers and were processed epoch-by-epoch using the three methods. The same observation data were also processed in a dual-frequency mode for comparison. The results show that, compared to the dual-frequency based solution, the single epoch ambiguity resolution success rate with triple frequency improved nearly 30 % for the short baselines (<20 km) and 100 % for the mid-length baselines (20–50 km) using the proposed modified stepwise AR method. 相似文献
20.
An approach to GLONASS ambiguity resolution 总被引:7,自引:2,他引:7
J. Wang 《Journal of Geodesy》2000,74(5):421-430
When processing global navigation satellite system (GLONASS) carrier phases, the standard double-differencing (DD) procedure
cannot cancel receiver clock terms in the DD phase measurement equations due to the multiple frequencies of the carrier phases.
Consequently, a receiver clock parameter has to be set up in the measurement equations in addition to baseline components
and DD ambiguities. The resulting normal matrix unfortunately becomes singular. Methods to deal with this problem have been
proposed in the literature. However, these methods rely on the use of pseudo-ranges. As pseudo-ranges are contaminated by
multi-path and hardware delays, biases in these pseudo-ranges are significant, which may result in unreliable ambiguity resolution.
A new approach is addressed that is not sensitive to the biases in the pseudo-ranges. The proposed approach includes such
steps as converting the carrier phases to their distances to cancel the receiver clock errors, and searching for the most
likely single-differenced (SD) ambiguity. Based on the results from the theoretical investigation, a practical procedure for
GLONASS ambiguity resolution is presented. The initial experimental results demonstrate that the proposed approach is useable
in cases of GLONASS and combined global positioning system (GPS) and GLONASS positioning.
Received: 19 August 1998 / Accepted: 12 November 1999 相似文献