scholarly journals Precision-Aided Partial Ambiguity Resolution Scheme for Instantaneous RTK Positioning

2021 ◽  
Vol 13 (15) ◽  
pp. 2904
Author(s):  
Juan Manuel Castro-Arvizu ◽  
Daniel Medina ◽  
Ralf Ziebold ◽  
Jordi Vilà-Valls ◽  
Eric Chaumette ◽  
...  
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Real Data ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Satellite Systems ◽  
Partial Ambiguity Resolution ◽  
Complete Vector ◽  
Global Navigation Satellite ◽  
Long Baselines

The use of carrier phase data is the main driver for high-precision Global Navigation Satellite Systems (GNSS) positioning solutions, such as Real-Time Kinematic (RTK). However, carrier phase observations are ambiguous by an unknown number of cycles, and their use in RTK relies on the process of mapping real-valued ambiguities to integer ones, so-called Integer Ambiguity Resolution (IAR). The main goal of IAR is to enhance the position solution by virtue of its correlation with the estimated integer ambiguities. With the deployment of new GNSS constellations and frequencies, a large number of observations is available. While this is generally positive, positioning in medium and long baselines is challenging due to the atmospheric residuals. In this context, the process of solving the complete set of ambiguities, so-called Full Ambiguity Resolution (FAR), is limiting and may lead to a decreased availability of precise positioning. Alternatively, Partial Ambiguity Resolution (PAR) relaxes the condition of estimating the complete vector of ambiguities and, instead, finds a subset of them to maximize the availability. This article reviews the state-of-the-art PAR schemes, addresses the analytical performance of a PAR estimator following a generalization of the Cramér–Rao Bound (CRB) for the RTK problem, and introduces Precision-Driven PAR (PD-PAR). The latter constitutes a new PAR scheme which employs the formal precision of the (potentially fixed) positioning solution as selection criteria for the subset of ambiguities to fix. Numerical simulations are used to showcase the performance of conventional FAR and FAR approaches, and the proposed PD-PAR against the generalized CRB associated with PAR problems. Real-data experimental analysis for a medium baseline complements the synthetic scenario. The results demonstrate that (i) the generalization for the RTK CRB constitutes a valid lower bound to assess the asymptotic behavior of PAR estimators, and (ii) the proposed PD-PAR technique outperforms existing FAR and PAR solutions as a non-recursive estimator for medium and long baselines.

scholarly journals Partial Carrier-Phase Integer Ambiguity Resolution for High Accuracy GNSS Positioning

2020 ◽  
Author(s):  
Andreas Brack
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Real Data ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Phase Measurements ◽  
Satellite Systems ◽  
Partial Ambiguity Resolution ◽  
Gnss Positioning ◽  
Global Navigation Satellite

Global navigation satellite systems provide ranging based positioning and timing services. The use of the periodic carrier-phase signals is the key to fast and accurate solutions, given that the inherent ambiguities of the carrier-phase measurements are correctly resolved. The idea of partial ambiguity resolution is to resolve a subset of all ambiguities, which enables faster solutions but does not fully exploit the high precision of the carrier-phase measurements. Theory, methods, and algorithms for partial ambiguity resolution are discussed and analyzed with simulated and real data.

scholarly journals A Refined SNR Based Stochastic Model to Reduce Site-Dependent Effects

2020 ◽  
Vol 12 (3) ◽  
pp. 493 ◽  
Author(s):  
Ruijie Xi ◽  
Xiaolin Meng ◽  
Weiping Jiang ◽  
Xiangdong An ◽  
Qiyi He ◽  
...  
Keyword(s):  
Stochastic Model ◽  
Data Processing ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Satellite System ◽  
Deformation Monitoring ◽  
Integer Ambiguity Resolution ◽  
Integer Ambiguity ◽  
Satellite Systems ◽  
Global Navigation Satellite

Site-dependent effects are now the key factors that restrict the high accuracy applications of Global Navigation Satellite System (GNSS) technology, such as deformation monitoring. To reduce the effects of non-line-of-sight (NLOS) signal and multipath, methods and models applied to both of the function model and stochastic model of least-squares (LS) have been proposed. However, the existing methods and models may not be convenient to use and not be appropriate to all GNSS satellites. In this study, the SNR features of GPS and GLONASS are analyzed first, and a refined SNR based stochastic model is proposed, in which the links between carrier phase precision and SNR observation have been reasonably established. Compared with the existing models, the refined model in this paper could be used in real-time and the carrier phase precision could be reasonably shown with the SNR data. More importantly, it is applicable to all GNSS satellite systems. Based on this model, the site observation environment can be assessed in advance to show the obstruction area. With a bridge deformation monitoring platform, the performance of this model was tested in the aspect of integer ambiguity resolution and data processing. The results show that, compared with the existing stochastic models, this model could have the highest integer ambiguity resolution success rate and the lowest noise level in the data processing time series with obvious obstruction beside the site.

scholarly journals GNSS RTK Positioning Augmented with Large LEO Constellation

2019 ◽  
Vol 11 (3) ◽  
pp. 228 ◽  
Author(s):  
Xingxing Li ◽  
Hongbo Lv ◽  
Fujian Ma ◽  
Xin Li ◽  
Jinghui Liu ◽  
...  
Keyword(s):  
Low Earth Orbit ◽  
Global Navigation Satellite Systems ◽  
Convergence Time ◽  
Current Status ◽  
Initial Assessment ◽  
Satellite Systems ◽  
Long Baseline ◽  
Leo Satellites ◽  
Global Navigation Satellite ◽  
Long Baselines

It is widely known that in real-time kinematic (RTK) solution, the convergence and ambiguity-fixed speeds are critical requirements to achieve centimeter-level positioning, especially in medium-to-long baselines. Recently, the current status of the global navigation satellite systems (GNSS) can be improved by employing low earth orbit (LEO) satellites. In this study, an initial assessment is applied for LEO constellations augmented GNSS RTK positioning, where four designed LEO constellations with different satellite numbers, as well as the nominal GPS constellation, are simulated and adopted for analysis. In terms of aforementioned constellations solutions, the statistical results of a 68.7-km baseline show that when introducing 60, 96, 192, and 288 polar-orbiting LEO constellations, the RTK convergence time can be shortened from 4.94 to 2.73, 1.47, 0.92, and 0.73 min, respectively. In addition, the average time to first fix (TTFF) can be decreased from 7.28 to 3.33, 2.38, 1.22, and 0.87 min, respectively. Meanwhile, further improvements could be satisfied in several elements such as corresponding fixing ratio, number of visible satellites, position dilution of precision (PDOP) and baseline solution precision. Furthermore, the performance of the combined GPS/LEO RTK is evaluated over various-length baselines, based on convergence time and TTFF. The research findings show that the medium-to-long baseline schemes confirm that LEO satellites do helpfully obtain faster convergence and fixing, especially in the case of long baselines, using large LEO constellations, subsequently, the average TTFF for long baselines has a substantial shortened about 90%, in other words from 12 to 2 min approximately by combining with the larger LEO constellation of 192 or 288 satellites. It is interesting to denote that similar improvements can be observed from the convergence time.

Precise carrier phase altimetry over lakes using dual-frequency reflected signals of the Global Navigation Satellite Systems (GNSS)

2021 ◽  
Author(s):  
Estel Cardellach ◽  
Weiqiang Li ◽  
Dallas Masters ◽  
Takayuki Yuasa ◽  
Franck Borde ◽  
...  
Keyword(s):  
Sea Ice ◽  
Carrier Phase ◽  
Radio Occultation ◽  
Global Navigation Satellite Systems ◽  
Data Sets ◽  
Dual Frequency ◽  
Effective Wavelength ◽  
Raw Data ◽  
Satellite Systems ◽  
Global Navigation Satellite

<p>Recently, different studies have shown evidence of signals transmitted by the Global Navigation Satellite Systems (GNSS), coherently reflected over some parts of the ocean, and received from cubesats. In particular, strong coherent scattering has been reported in regions with low water surface roughness as those near continental masses and in atolls. Over open ocean, few coherent signals were reported to be found, although the data sets were somewhat limited and certainly not exhaustive. The level of coherence in reflected GNSS signals depends on the roughness of the  surface (i.e. significant wave height and small scale ripples and waves induced by the wind), the viewing geometry (i.e. incidence angle, or equivalently, elevation angle of the GNSS satellite as seen from the point of reflection), propagation effects (namely ionospheric disturbances) and on the frequency (i.e. particular GNSS band, like L1/E1, L2 or L5/E5). These coherent measurements over ocean follow earlier evidence of coherent GNSS reflections over sea ice which date back to 2005, the time of UK-DMC mission. More recently, Sea Ice Thickness (SIT) retrievals have also been carried out with this technique, at an accuracy comparable to that of SMOS.</p><p>All the observations referred so far were done at a single frequency, L1/E1. So, there is an interest to explore the coherence at the other main GNSS bands, i.e. L2 and L5/E5 as well as to the widelane combinations between them (linear combinations of carrier-phase measurements, of longer effective wavelength). Spire Global radio occultation cubesats work at L1 and L2 frequency bands, and therefore provide unique dual-frequency raw data sets of reflected signals over open ocean, sea ice and inland water bodies. With these, it is possible to study the coherence of these targets at each of the bands and at their widelane combination, as well as the performance of altimetric retrievals at grazing angles of observation (very slant geometries, which facilitate coherence properties of the scattering). The dual-frequency observations can correct the ionospheric effects, and their widelane combinations, of longer effective wavelength, might expand the conditions for coherence. The fact that this new approach is fully compatible with small GNSS radio occultation payloads and missions, might represent a low cost source of precise altimetry to complement larger dedicated missions.</p><p>An ESA research study involving Spire Global and IEEC aims at studying this new potential altimetric technique. Raw data acquisitions from limb-looking antennas of Spire’s cubesat constellation were selected to be geographically and time collocated with ESA Sentinel 3A and 3B passes in order to compare the results of coherence and altimetry. For this study, the raw data at two frequencies, acquired at 6.2 Mbps, are shifted to intermediate frequencies and downloaded to the ground without any further processing. In-house software receivers are then applied to generate the reflected echoes or waveforms, and to track the phase of the carrier signals. Precise altimetry (a few cm in 20 ms integration) is then possible from these observables. The results of this activity will be shown, focusing on altimetric retrievals over large lakes.</p>

scholarly journals Theoretical Upper Bound and Lower Bound for Integer Aperture Estimation Fail-Rate and Practical Implications

2012 ◽  
Vol 66 (3) ◽  
pp. 321-333 ◽  
Author(s):  
Tao Li ◽  
Jinling Wang
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Satellite Systems ◽  
Gnss Positioning ◽  
Integer Aperture Estimation ◽  
Ambiguity Validation ◽  
Global Navigation Satellite ◽  
Practical Implications

Integer ambiguity validation is pivotal in precise positioning with Global Navigation Satellite Systems (GNSS). Recent research has shown traditionally used ambiguity validation methods can be classified as members of the Integer Aperture (IA) estimators, and by the virtue of the IA estimation, a user controllable IA fail-rate is preferred. However, an appropriately chosen fail-rate is essential for ambiguity validation. In this paper, the upper bound and the lower bound for the IA fail-rate, which are extremely useful even at the designing stage of a GNSS positioning system, have been analysed, and numerical results imply that a meaningful IA fail-rate should be within this range.

Double-Difference Carrier-Phase Network Solution Using Nominal Gnss Constellations (Future Perception)

2008 ◽  
Vol 43 (2) ◽  
pp. 65-73
Author(s):  
A. Farah
Keyword(s):  
Carrier Phase ◽  
Satellite System ◽  
Global Navigation Satellite Systems ◽  
Double Difference ◽  
Navigation Satellite ◽  
Network Solution ◽  
Satellite Systems ◽  
Performance Improvements ◽  
Global Navigation ◽  
Global Navigation Satellite

Double-Difference Carrier-Phase Network Solution Using Nominal Gnss Constellations (Future Perception)Global Navigation Satellite Systems (GNSS) have an endless number of applications in industry, science, military, transportation and recreation & sports. Two systems are currently in operation namely GPS (the USA Global Positioning System) and GLONASS (the Russian GLObal NAvigation Satellite System), and a third is planned, the European satellite navigation system GALILEO. The potential performance improvements achievable through combining these systems could be significant and expectations are high. The need is inevitable to explore the future of positioning accuracy using different nominal constellations. In this research paper, Bernese 5.0 software could be modified to simulate and process GNSS observations from three different constellations (GPS, Glonass and Galileo) using different combinations. This study presents results of double-difference carrier-phase solution for five stations-network using the three constellations and different combinations.

scholarly journals Measurement Signal Quality Assessment on All Available and New Signals of Multi-GNSS (GPS, GLONASS, Galileo, BDS, and QZSS) with Real Data

2015 ◽  
Vol 69 (2) ◽  
pp. 313-334 ◽  
Author(s):  
Yiming Quan ◽  
Lawrence Lau ◽  
Gethin W. Roberts ◽  
Xiaolin Meng
Keyword(s):  
Attitude Determination ◽  
Real Data ◽  
Global Navigation Satellite Systems ◽  
Double Difference ◽  
Signal Quality ◽  
Early Assessment ◽  
Satellite Systems ◽  
Agricultural Applications ◽  
Short Baselines ◽  
Global Navigation Satellite

Global Navigation Satellite Systems (GNSS) Carrier Phase (CP)-based high-precision positioning techniques have been widely used in geodesy, attitude determination, engineering survey and agricultural applications. With the modernisation of GNSS, multi-constellation and multi-frequency data processing is one of the foci of current GNSS research. The GNSS development authorities have better designs for the new signals, which are aimed for fast acquisition for civil users, less susceptible to interference and multipath, and having lower measurement noise. However, how good are the new signals in practice? The aim of this paper is to provide an early assessment of the newly available signals as well as assessment of the other currently available signals. The signal quality of the multi-GNSS (GPS, GLONASS, Galileo, BDS and QZSS) is assessed by looking at their zero-baseline Double Difference (DD) CP residuals. The impacts of multi-GNSS multi-frequency signals on single-epoch positioning are investigated in terms of accuracy, precision and fixed solution availability with known short baselines.

scholarly journals Context-Aware Sensor Uncertainty Estimation for Autonomous Vehicles

Vehicles ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 721-735
Author(s):  
Mohammed Alharbi ◽  
Hassan A. Karimi
Keyword(s):  
Autonomous Vehicles ◽  
Real Data ◽  
Global Navigation Satellite Systems ◽  
Learning Approach ◽  
Context Aware ◽  
Satellite Systems ◽  
Sensor Performance ◽  
Machine Learning Approach ◽  
Global Navigation Satellite ◽  
Data Acquisition Process

Sensor uncertainty significantly affects the performance of autonomous vehicles (AVs). Sensor uncertainty is predominantly linked to sensor specifications, and because sensor behaviors change dynamically, the machine learning approach is not suitable for learning them. This paper presents a novel learning approach for predicting sensor performance in challenging environments. The design of our approach incorporates both epistemic uncertainties, which are related to the lack of knowledge, and aleatoric uncertainties, which are related to the stochastic nature of the data acquisition process. The proposed approach combines a state-based model with a predictive model, where the former estimates the uncertainty in the current environment and the latter finds the correlations between the source of the uncertainty and its environmental characteristics. The proposed approach has been evaluated on real data to predict the uncertainties associated with global navigation satellite systems (GNSSs), showing that our approach can predict sensor uncertainty with high confidence.

Impact of Decorrelation on Success Rate Bounds of Ambiguity Estimation

2016 ◽  
Vol 69 (5) ◽  
pp. 1061-1081 ◽  
Author(s):  
Lei Wang ◽  
Yanming Feng ◽  
Jiming Guo ◽  
Charles Wang
Keyword(s):  
Success Rate ◽  
Ambiguity Resolution ◽  
Performance Measure ◽  
Global Navigation Satellite Systems ◽  
Navigation Systems ◽  
Success Rates ◽  
Satellite Systems ◽  
Integer Estimation ◽  
Ambiguity Estimation ◽  
Global Navigation Satellite

Reliability is an important performance measure of navigation systems and this is particularly true in Global Navigation Satellite Systems (GNSS). GNSS positioning techniques can achieve centimetre-level accuracy which is promising in navigation applications, but can suffer from the risk of failure in ambiguity resolution. Success rate is used to measure the reliability of ambiguity resolution and is also critical in integrity monitoring, but it is not always easy to calculate. Alternatively, success rate bounds serve as more practical ways to assess the ambiguity resolution reliability. Meanwhile, a transformation procedure called decorrelation has been widely used to accelerate ambiguity estimations. In this study, the methodologies of bounding integer estimation success rates and the effect of decorrelation on these success rate bounds are examined based on simulation. Numerical results indicate decorrelation can make most success rate bounds tighter, but some bounds are invariant or have their performance degraded after decorrelation. This study gives a better understanding of success rate bounds and helps to incorporate decorrelation procedures in success rate bounding calculations.

Sign in / Sign up

Export Citation Format

Share Document