scholarly journals The Application of Robust Least Squares Method in Frequency Lock Loop Fusion for Global Navigation Satellite System Receivers

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1224 ◽  
Author(s):  
Mengyue Han ◽  
Qian Wang ◽  
Yuanlan Wen ◽  
Min He ◽  
Xiufeng He
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Satellite System ◽  
Complex Environment ◽  
Tracking Accuracy ◽  
Proposed Model ◽  
Robust Least Squares ◽  
Promising Application ◽  
Overall Performance ◽  
Global Navigation Satellite

The tracking accuracy of a traditional Frequency Lock Loop (FLL) decreases significantly in a complex environment, thus reducing the overall performance of a satellite receiver. In order to ensure high tracking accuracy of a receiver in a complex environment, this paper proposes a new tracking loop combining the vector FLL (VFLL) with a robust least squares method, which accurately matches the weights of received signals of different qualities to ensure high positioning accuracy. The weights of received signals are selected at the signal level, not at the observation level. In this paper, the ranges of strong and weak signals of the loop are determined according to the different expressions of the distribution function at different signal strengths, and the concept of loop segmentation is introduced. The segmentation results of the FLL are taken as a basis of the weight selection, and then combined with the Institute of Geodesy and Geophysics (IGGIII) weight function to obtain the equivalent weight matrix; the experiments are conducted to prove the advantages of the proposed method over the traditional methods. The experimental results show that the proposed VFLL tracking method has strong denoising capability under both normal- signal and harsh application environment conditions. Accordingly, the proposed model has a promising application perspective.

A Signal Quality Monitoring Based on Least-Squares for Global Navigation Satellite System

2011 ◽  
Vol 383-390 ◽  
pp. 7582-7587
Author(s):  
Hai Long Chen ◽  
Yan Bo Zhu ◽  
Rui Xue
Keyword(s):  
Least Squares ◽  
Global Navigation Satellite System ◽  
Least Squares Method ◽  
Satellite System ◽  
Quality Monitoring ◽  
Quadratic Model ◽  
Signal Quality ◽  
Navigation Satellite ◽  
Global Navigation ◽  
Global Navigation Satellite

Signal Quality Monitoring (SQM) proposes to detect anomalous Global Navigation Satellite System (GNSS) signal distortions primarily through the using the multi-correlator receivers. These receivers employ three or more correlator pairs per channel-each slaved to tracking pairs. Then the measurements from each channel are transformed to form detection metrics. However, previously such some metrics were only simple algebraic combinations of the measurements and did not describe truly the characteristics of the correlation peak. This paper introduced a metric which uses measurements of each channel to fit the quadratic model with least-squares method to monitor the GNSS signal.

GPS-BDS-Galileo double-differenced stochastic model refinement based on least-squares variance component estimation

2021 ◽  
pp. 1-16
Author(s):  
Hong Hu ◽  
Xuefeng Xie ◽  
Jingxiang Gao ◽  
Shuanggen Jin ◽  
Peng Jiang
Keyword(s):  
Stochastic Model ◽  
Least Squares ◽  
Stochastic Models ◽  
Variance Component ◽  
Satellite System ◽  
Variance Component Estimation ◽  
Short Baseline ◽  
Component Estimation ◽  
Zero Baseline ◽  
Global Navigation Satellite

Abstract Stochastic models are essential for precise navigation and positioning of the global navigation satellite system (GNSS). A stochastic model can influence the resolution of ambiguity, which is a key step in GNSS positioning. Most of the existing multi-GNSS stochastic models are based on the GPS empirical model, while differences in the precision of observations among different systems are not considered. In this paper, three refined stochastic models, namely the variance components between systems (RSM1), the variances of different types of observations (RSM2) and the variances of observations for each satellite (RSM3) are proposed based on the least-squares variance component estimation (LS-VCE). Zero-baseline and short-baseline GNSS experimental data were used to verify the proposed three refined stochastic models. The results show that, compared with the traditional elevation-dependent model (EDM), though the proposed models do not significantly improve the ambiguity resolution success rate, the positioning precision of the three proposed models has been improved. RSM3, which is more realistic for the data itself, performs the best, and the precision at elevation mask angles 20°, 30°, 40°, 50° can be improved by 4⋅6%, 7⋅6%, 13⋅2%, 73⋅0% for L1-B1-E1 and 1⋅1%, 4⋅8%, 16⋅3%, 64⋅5% for L2-B2-E5a, respectively.

scholarly journals Design of Unambiguous Combined Tracking Loop for GNSS Complex Subcarrier Signal

2018 ◽  
Vol 36 (1) ◽  
pp. 176-181
Author(s):  
Xianzhi Luo ◽  
Hongwei Zhao ◽  
Hao Yan
Keyword(s):  
Satellite System ◽  
Tracking Loop ◽  
Tracking Accuracy ◽  
Multiple Correlation ◽  
Data Simulation ◽  
Side Peak ◽  
Main Loop ◽  
Modulation Signal ◽  
Global Navigation Satellite ◽  
Complex Exponential

Complex subcarrier modulation signal, is a kind of BOC signal which is used complex exponential function as subcarrier, has been widely applied in GNSS(Global Navigation satellite system). The existence of multiple correlation peaks of the autocorrelation function of the complex subcarrier signal, will cause the acquisition error and tracking to the side peak when the signal is synchronized. To solve this problem, an unambiguous combined tracking loop for complex subcarrier signals is proposed. In this loop architecture, the main loop completes the coarse synchronization with BPSK-like algorithm, and the assisted loop realizes the accurate tracking together main loop. In this paper, the dual estimate tracking algorithm and the side-peak cancellation scheme are employed respectively in the assisted loop. The performance of tracking accuracy and anti-multipath capability of the proposed architecture is analyzed, and the practicability is verified by using the actual collected data. Simulation and experimental results show that the tracking structure proposed in this paper is practical and has good performance of anti-noise and anti-multipath.

Understanding Quantitative Performance of Large Standoff Magnetometry in Detecting Live Gas Pipeline Anomalies With Stress Estimation

2018 ◽  
Author(s):  
Tianzong (David) Xu
Keyword(s):  
Satellite System ◽  
Measurement Technology ◽  
Location Accuracy ◽  
Basic Physics ◽  
Leakage Measurement ◽  
Quantitative Performance ◽  
Stress Estimation ◽  
Overall Performance ◽  
Global Navigation Satellite ◽  
Flux Leakage

Large standoff magnetometry (LSM) is an emerging non-intrusive, above-ground, passive geo-magnetization flux leakage measurement technology to detect pipeline features or anomalies associated with elevated stresses. Although many promising field trial results have been reported in the past, its overall performance still has not reached sufficient consistency and reliability. This paper presents PG&E’s effort in gaining some fundamental understanding of the current LSM technology and its qualitative & quantitative performance. Specifically location accuracy of girth weld, casing end, dent and landslide damage is analyzed with references to inline inspection (ILI) and excavation data. In addition, basic physics of LSM stress quantification is examined using references of a full-scale finite element stress analysis on selected plain dents. The outcomes indicate advanced global navigation satellite system (GNSS) tool plus capability of identifying girth weld are important to achieve good anomaly location accuracy especially as LSM tends to report more indications than other inspection technologies in current practice. The LSM stress estimation and its comparison to pipe’s specified minimum yield strength (SMYS) may be only good quantitatively within magneto-elastic regime where localized stress concentration zones (SCZs) are under elastic stress loading only and without presence of residual plastic stress.

scholarly journals A Novel Dynamical Filter Based on Multi-Epochs Least-Squares to Integrate the Carrier Phase and Pseudorange Observation for GNSS Measurement

2020 ◽  
Vol 12 (11) ◽  
pp. 1762
Author(s):  
Fangchao Li ◽  
Jingxiang Gao ◽  
Panos Psimoulis ◽  
Xiaolin Meng ◽  
Fuyang Ke
Keyword(s):  
Least Squares ◽  
Carrier Phase ◽  
Satellite System ◽  
Convergence Speed ◽  
Least Square ◽  
Phase Observation ◽  
Carrier Phase Observation ◽  
Lower Accuracy ◽  
Accuracy Difference ◽  
Global Navigation Satellite

The high noise of pseudorange and the ambiguity of carrier phase observation restrain the GNSS (Global Navigation Satellite System) application in military, industrial, and agricultural, to name a few. Thus, it is crucial for GNSS technology to integrate the pseudorange and carrier phase observations. However, the traditional method proposed by Hatch has obtained only a low convergence speed and precision. For higher convergence speed and precision of the smoothed pseudorange, aiming to improve positioning accuracy and expand the application of GNSS, we introduced a new method named MELS (Multi-Epochs Least-Squares) that considered the cross-correlation of the estimating parameters inspired by DELS (Double-Epochs Least-Square). In this study, the ionospheric delay was compensated, and so its impact was limited to the performance of the filters, and then exploited the various filters to integrate carrier phase observation and pseudorange. We compared the various types of Hatch’s filter and LS (Least-Square) methods using simulation datasets, which confirmed that the types of LS method provided a smaller residual error and a faster convergence speed than Hatch’s method under various precisions of raw pseudorange. The experimental results from the measured GNSS data showed that LS methods provided better performance than Hatch’s methods at E and U directions and a lower accuracy at N direction. Nevertheless, the types of LS method and Hatch’s methods improved about 12% and 9–10% at the 3D direction, respectively, which illustrated the accumulating improvement at the enhanced directions was more than the decreased direction, proving that the types of LS method resulted to better performance than the Hatch’s filters. Additionally, the curve of residual and precision based on various LS methods illustrated that the MELS only provided a millimeter accuracy difference compared with DELS, which was proved by the simulated and measured GNSS datasets.

Sign in / Sign up

Export Citation Format

Share Document