An Algorithm of Detecting and Repairing One Cycle Wide Lane Integer Ambiguity Error for Short Baseline

2016 ◽  
Author(s):  
Shuo Liu ◽  
Lei Zhang ◽  
Jian Li ◽  
Meina Li
Keyword(s):  
Integer Ambiguity ◽  
Short Baseline ◽  
Wide Lane

An Improved Geometry-free Three Carrier Ambiguity Resolution Method for the BeiDou Navigation Satellite System

2016 ◽  
Vol 69 (6) ◽  
pp. 1393-1408 ◽  
Author(s):  
Xing Wang ◽  
Wenxiang Liu ◽  
Guangfu Sun
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Success Probability ◽  
Satellite System ◽  
Observation Data ◽  
Short Baseline ◽  
Long Baseline ◽  
Triple Frequency ◽  
Wide Lane ◽  
Three Carrier Ambiguity Resolution

BeiDou satellites transmit triple-frequency signals, which bring substantial benefits to carrier phase Ambiguity Resolution (AR). The traditional geometry-free model Three-Carrier Ambiguity Resolution (TCAR) method looks for a suitable combination of carrier phase and code-range observables by searching and comparing in the integer range, which limits the AR success probability. By analysing the error characteristics of the BeiDou triple-frequency observables, we introduce a new procedure to select the optimal combination of carrier phase and code observables to resolve the resolution of Extra-Wide-Lane (EWL) and Wide-Lane (WL) ambiguity. We also investigate a geometry-free and ionosphere-eliminated method for AR of the Medium-Lane (ML) and Narrow-Lane (NL) observables. In order to evaluate the performance of the improved TCAR method, real BeiDou triple-frequency observation data for different baseline cases were collected and processed epoch-by-epoch. The results show that the improved geometry-free TCAR method increases the single epoch AR success probability by up to 90% for short baseline and 80% for long baseline. The A perfect (100%) AR success probability can also be effortlessly achieved by averaging the float ambiguities over just tens of epochs.

scholarly journals Assessment of GNSS Orthogonal Transformation Model

2012 ◽  
Vol 65 (3) ◽  
pp. 561-570 ◽  
Author(s):  
Wantong Chen ◽  
Yanzhong Zhang
Keyword(s):  
Orthogonal Transformation ◽  
Transformation Method ◽  
Transformation Model ◽  
Integer Ambiguity ◽  
Baseline Model ◽  
Short Baseline ◽  
Conditional Least Squares ◽  
Important Field ◽  
Positioning Technique ◽  
The Mathematical Model

GNSS relative positioning technique is an important field of study, in which the standard ‘GNSS Baseline Model’ is often used. Differencing between observation equations is used to construct the mathematical model, since this method can eliminate some common errors in the GNSS signal measurements. The ‘Orthogonal Transformation’ method can also construct the GNSS Baseline Model. However, as is described by some scholars, this model may avoid some drawbacks of Double Differencing (DD) while maintaining all the advantages. For comparison purposes, this model is evaluated and the theoretical equivalence of both approaches is proved for the short baseline from two aspects: the Integer Ambiguity Resolution and the conditional least-squares baseline vector.

scholarly journals Improvement of Multi-GNSS Precision and Success Rate Using Realistic Stochastic Model of Observations

2021 ◽  
Vol 14 (1) ◽  
pp. 60
Author(s):  
Farinaz Mirmohammadian ◽  
Jamal Asgari ◽  
Sandra Verhagen ◽  
Alireza Amiri-Simkooei
Keyword(s):  
Stochastic Model ◽  
Data Processing ◽  
Success Rate ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Double Difference ◽  
Unbiased Estimation ◽  
Data Sets ◽  
Short Baseline ◽  
Gnss Data

With the advancement of multi-constellation and multi-frequency global navigation satellite systems (GNSSs), more observations are available for high precision positioning applications. Although there is a lot of progress in the GNSS world, achieving realistic precision of the solution (neither too optimistic nor too pessimistic) is still an open problem. Weighting among different GNSS systems requires a realistic stochastic model for all observations to achieve the best linear unbiased estimation (BLUE) of unknown parameters in multi-GNSS data processing mode. In addition, the correct integer ambiguity resolution (IAR) becomes crucial in shortening the Time-To-Fix (TTF) in RTK, especially in challenging environmental conditions. In general, it is required to estimate various variances for observation types, consider the correlation between different observables, and compensate for the satellite elevation dependence of the observable precision. Quality control of GNSS signals, such as GPS, GLONASS, Galileo, and BeiDou can be performed by processing a zero or short baseline double difference pseudorange and carrier phase observations using the least-squares variance component estimation (LS-VCE). The efficacy of this method is investigated using real multi-GNSS data sets collected by the Trimble NETR9, SEPT POLARX5, and LEICA GR30 receivers. The results show that the standard deviation of observations depends on the system and the observable type in which a particular receiver could have the best performance. We also note that the estimated variances and correlations among different observations are also dependent on the receiver type. It is because the approaches utilized for the recovery techniques differ from one type of receiver to another kind. The reliability of IAR will improve if a realistic stochastic model is applied in single or multi-GNSS data processing. According to the results, for the data sets considered, a realistic stochastic model can increase the computed empirical success rate to 100% in multi-GNSS as well as a single system. As mentioned previously, the realistic precision of the solution can be achieved with a realistic stochastic model. However, using the estimated stochastic model, in fact, leads to better precision and accuracy for the estimated baseline components, up to 39% in multi-GNSS.

Performance of GPS Precise Time and Frequency Transfer with Integer Ambiguity Resolution

2021 ◽  
Author(s):  
Pengfei Zhang ◽  
Rui Tu ◽  
Xiaochun Lu ◽  
Yuping Gao ◽  
Lihong Fan
Keyword(s):  
Real Time ◽  
Ambiguity Resolution ◽  
Integer Ambiguity Resolution ◽  
Integer Ambiguity ◽  
Convergence Time ◽  
Processing Modes ◽  
Wide Lane ◽  
Frequency Transfer ◽  
Fixed Solution ◽  
Precise Time

Abstract The global positioning system (GPS) carrier-phase (CP) technique is a widely used spatial tool for remote precise time and frequency transfer. However, the performance of traditional GPS time and frequency transfer has been limeted because the ambiguity paramter is still the float solution. This study focuses on the performance of GPS precise time and frequency transfer with integer ambiguity resolution and discusses the corresponding mathematical model. Fractional-cycle bias (FCB) products were estimated by using an ionosphere-free combination. The results show that the satellite wide-lane (WL) FCB products are stable, with a standard deviation (STD) of 0.006 cycles. The narrow-lane (NL) FCB products were estimated over 15 min with the STD of 0.020 cycles. More than 98% of the WL and NL residuals are smaller than 0.25 cycles, which helps to fix the ambiguity into integers during the time and frequency transfer. Subsequently, the performances of the time transfers with integer ambiguity resolution at two time links between international laboratories were assessed in real-time and post-processing modes and compared. The results show that fixing the ambiguity into an integer in the real-time mode significantly decreases the convergence time compared with the traditional float approach. The improvement is ~49.5%. The frequency stability of the fixed solution is notably better than that of the float solution. Improvements of 48.15% and 27.9% were determined for the IENG–USN8 and WAB2–USN8 time links, respectively.

scholarly journals Detection and elimination method for deception jamming based on an antenna array

2018 ◽  
Vol 14 (5) ◽  
pp. 155014771877446 ◽  
Author(s):  
Shuyan Ni ◽  
Jianhua Cui ◽  
Naiping Cheng ◽  
Yurong Liao
Keyword(s):  
Global Positioning System ◽  
Measurement Errors ◽  
Integer Ambiguity ◽  
Double Difference ◽  
Fast Method ◽  
Short Baseline ◽  
Elimination Method ◽  
Medium Length ◽  
Global Positioning ◽  
Jamming Detection

A global positioning system is an important way of locating an aircraft, while deception jamming can affect the positioning accuracy of such navigation. Considering this, a detection and elimination method for deception jamming is proposed based on a specially designed array for the aircraft. The jamming is detected by comparing the double-difference observation of the carrier phases of two different signals to a certain threshold derived according to the measurement errors of the receiver. To estimate the jamming direction with high accuracy, meanwhile considering the feasibility of airborne installation, a novel configurated array combining medium-length baseline with short baseline is designed, and a fast method to solve the integer ambiguity is discussed. After jamming detection, the nulling of the array beam is pointed to the jamming source through the orthogonal vector weighting to suppress jamming. The validity of the method is verified by computer simulations.

scholarly journals Optimization and selection of Galileo triple-frequency carrier linear combination

2021 ◽  
Vol 54 (1-2) ◽  
pp. 116-128
Author(s):  
Jun Wang ◽  
Xurong Dong ◽  
Wei Fu ◽  
Di Yan ◽  
Zengkai Shi
Keyword(s):  
Linear Combination ◽  
Low Noise ◽  
Integer Ambiguity ◽  
Convergence Time ◽  
Linear Combinations ◽  
Long Wavelength ◽  
Triple Frequency ◽  
Cycle Slip Detection ◽  
Wide Lane ◽  
Speed Up

The triple-frequency linear combination with a low noise, a long wavelength, and a weak ionosphere is beneficial to effectively eliminate or weaken the common errors, advance the reliability of cycle slip detection and repair, and speed up the convergence time of fixed ambiguity. By establishing the Galileo triple-frequency carrier linear combination model, three types of linear combinations are derived: Geometry-free (GF) combinations, minimum noise (MN) combinations, and ionosphere-free (IF) combinations. The geometric relationships of these linear combinations are displayed in the form of image. The results indicate that the angle formed by the IF combinations and the MN combinations is between 75.02° and 86.01°, which also illustrates that it is more difficult to meet the carrier phase combinations with a low noise and a weak ionosphere. Moreover, to guarantee the integer cycle characteristics of ambiguity, the combination coefficient must be an integer. Galileo triple-frequency linear combination is solved utilizing the extremum method. To sum up, the sum of the coefficients of the extra wide lane (EWL) combinations and wide lane (WL) combinations is zero, and the sum of the coefficients of the narrow lane (NL) combinations is one. (0, 1, −1) is the optimal triple-frequency linear combination in Galileo. Three independent linear combinations are selected separately from the EWL, WL, and NL to jointly solve the integer ambiguity. Further, it creates a prerequisite for high-precision and real-time kinematic positioning.

scholarly journals High-Accuracy Attitude Determination Using Single-Difference Observables Based on Multi-Antenna GNSS Receiver with a Common Clock

2021 ◽  
Vol 13 (19) ◽  
pp. 3977
Author(s):  
Chenglong Zhang ◽  
Danan Dong ◽  
Wen Chen ◽  
Miaomiao Cai ◽  
Yu Peng ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Attitude Determination ◽  
Clock Synchronization ◽  
Integer Ambiguity ◽  
Double Difference ◽  
Fiber Optic Gyroscope ◽  
Short Baseline ◽  
Practical Applications ◽  
Gnss Receiver ◽  
Single Difference

A global navigation satellite system (GNSS) receiver with multi-antenna using clock synchronization technology is a powerful piece of equipment for precise attitude determination and reducing costs. The single-difference (SD) can eliminate both the satellites and receiver clock errors with the common clock between antennas, which benefits the GNSS short-baseline attitude determination due to its lower noise, higher redundancy and stronger function model strength. However, the existence of uncalibrated phase delay (UPD) makes it difficult to obtain fixed SD attitude solutions. Therefore, the key problem for the fixed SD attitude solutions is to separate the SD UPD and fix the SD ambiguities into integers between antennas. This article introduces the one-step ambiguity substitution approach to separate the SD UPD, through which we merge the SD UPD parameter with the SD ambiguity of the reference satellite ambiguity as the new SD UPD parameter. Reconstructing the other SD ambiguities, the rank deficiency can be remedied by nature, and the new SD ambiguities can have a natural integer feature. Finally, the fixed SD baseline and attitude solutions are obtained by combining the ambiguity substitution approach with integer ambiguity resolution (IAR). To verify the effect of the ambiguity substitution approach and the advantages of the SD observables with a common clock in practical applications, we conducted static, kinematic, and vehicle experiments. In static experiments, the root mean squared errors (RMSEs) of the yaw and pitch angles obtained by the SD observables with a common clock were improved by approximately 80% and 93%, respectively, compared to double-difference (DD) observables with a common clock in multi-day attitude solutions. The kinematic results show that the dispersion of the SD-Fix in the pitch angle is two times less that of the DD-Fix, and the standard deviations (STDs) of the pitch angle for SD-Fix can reach 0.02°. Based on the feasibility, five bridges with low pitch angles in the vehicle experiment environment, which the DD observables cannot detect, were detected by the SD observables with a common clock. The attitude angles obtained by the SD observables were also consistent with the fiber optic gyroscope (FOG) inertial navigation system (INS). This research on the SD observables with a common clock provides higher accuracy.

scholarly journals Accuracy Evaluation of Ionospheric Delay from Multi-Scale Reference Networks and Its Augmentation to PPP during Low Solar Activity

2021 ◽  
Vol 10 (8) ◽  
pp. 516
Author(s):  
Lewen Zhao ◽  
Jan Douša ◽  
Pavel Václavovic
Keyword(s):  
Solar Activity ◽  
Ambiguity Resolution ◽  
Periodic Variation ◽  
Ionospheric Delay ◽  
Integer Ambiguity ◽  
Activity Period ◽  
Accuracy Evaluation ◽  
Short Baseline ◽  
Hardware Biases ◽  
Global Ionosphere Map

The Precise Point Positioning (PPP) with fast integer ambiguity resolution (PPP-RTK) is feasible only if the solution is augmented with precise ionospheric parameters. The vertical ionospheric delays together with the receiver hardware biases, are estimated simultaneously based on the uncombined PPP model. The performance of the ionospheric delays was evaluated and applied in the PPP-RTK demonstration during the low solar activity period. The processing was supported by precise products provided by Deutsches GeoForschungsZentrum Potsdam (GFZ) and also by real-time products provided by the National Centre for Space Studies (CNES). Since GFZ provides only precise orbits and clocks, other products needed for ambiguity resolution, such as phase biases, were estimated at the Geodetic Observatory Pecny (GOP). When ambiguity parameters were resolved as integer values in the GPS-only solution, the initial convergence period was reduced from 30 and 20 min to 24 and 13 min when using CNES and GFZ/GOP products, respectively. The accuracy of ionospheric delays derived from the ambiguity fixed PPP, and the CODE global ionosphere map were then assessed. Comparison of ambiguity fixed ionospheric delay obtained at two collocated stations indicated the accuracy of 0.15 TECU for different scenarios with more than 60% improvement compared to the ambiguity float PPP. However, a daily periodic variation can be observed from the multi-day short-baseline ionospheric residuals. The accuracy of the interpolated ionospheric delay from global maps revealed a dependency on the location of the stations, ranging from 1 to 3 TECU. Precise ionospheric delays derived from the EUREF permanent network with an inter-station distance larger than 73 km were selected for ionospheric modeling at the user location. Results indicated that the PPP ambiguity resolution could be achieved within three minutes. After enlarging the inter-station distance to 209 km, ambiguity resolution could also be achieved within several minutes.

QIF-based GPS Long-baseline Ambiguity Resolution with the Aid of Atmospheric Delays Determined by PPP

2016 ◽  
Vol 69 (6) ◽  
pp. 1278-1292 ◽  
Author(s):  
Baocheng Zhang ◽  
Yunbin Yuan ◽  
Yanju Chai
Keyword(s):  
Ambiguity Resolution ◽  
Integer Ambiguity ◽  
Long Baseline ◽  
Integer Rounding ◽  
Wide Lane ◽  
Set Up ◽  
Time Required ◽  
Tropospheric Delays ◽  
Atmospheric Delays ◽  
Long Baselines

The Global Positioning System (GPS) long-baseline set up has been widely employed to generate high-accuracy positioning, timing and atmospheric information. Bernese GPS software adopts two appropriate strategies for long-baseline Integer Ambiguity Resolution (IAR): Quasi Ionosphere-Free (QIF) and Wide-lane/Narrow-lane (WN). With the goal of reasonably shortening the time required for long-baseline IAR, we propose the Precise Point Positioning (PPP) method for estimating, on a per receiver basis, the Zenith Tropospheric Delays (ZTDs) and the Slant Ionospheric Delays (SIDs) from zero-differenced, uncombined GPS observables. We then reformulate these PPP-derived ZTDs and SIDs into two types of atmospheric constraints with proper uncertainties that could be readily assimilated into the process of IAR with the QIF. Our numerical tests based on five independent long-baselines (>1,000 kilometres) suggest that the empirical precision of PPP-derived ZTDs (SIDs) is always better than 2 (10) centimetres. The modified QIF would be able to correctly resolve at least 98% and 88% of the wide- and narrow-lane ambiguities for all the long-baselines relying on the very simple integer rounding method. However, under the same condition, the WN can only get the correct integers of 76·6% wide-lane ambiguities and 55·2% narrow-lane ones.

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