scholarly journals GNSS Precise Relative Positioning Using A Priori Relative Position in a GNSS Harsh Environment

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1355
Author(s):  
Euiho Kim
Keyword(s):  
Carrier Phase ◽  
Low Cost ◽  
A Priori ◽  
Field Tests ◽  
Satellite System ◽  
Integer Ambiguity ◽  
Double Difference ◽  
Baseline Length ◽  
Harsh Environment ◽  
Relative Positioning

To enable Global Navigation Satellite System (GNSS)-based precise relative positioning, real-time kinematic (RTK) systems have been widely used. However, an RTK system often suffers from a wrong integer ambiguity fix in the GNSS carrier phase measurements and may take a long initialization time over several minutes, particularly when the number of satellites in view is small. To facilitate a reliable GNSS carrier phase-based relative positioning with a small number of satellites in view, this paper introduces a novel GNSS carrier phase-based precise relative positioning method that uses a fixed baseline length as well as heading measurements in the beginning of the operation, which allows the fixing of integer ambiguities with rounding schemes in a short time. The integer rounding scheme developed in this paper is an iterative process that sequentially resolves integer ambiguities, and the sequential order of the integer ambiguity resolution is based on the required averaging epochs that vary for each satellite depending on the geometry between the baseline and the double difference line-of-sight vectors. The required averaging epochs with respect to various baseline lengths and heading measurement uncertainties were analyzed through simulations. Static and dynamic field tests with low cost GNSS receivers confirmed that the positioning accuracy of the proposed method was better than 10 cm and significantly outperformed a conventional RTK solution in a GNSS harsh environment.

Low Cost AHRS Aids GPS Attitude Navigation System

2014 ◽  
Vol 536-537 ◽  
pp. 748-755
Author(s):  
Tong Yue Gao ◽  
Hai Lang Ge
Keyword(s):  
Navigation System ◽  
Carrier Phase ◽  
Phase Measurement ◽  
Low Cost ◽  
Integer Ambiguity ◽  
Baseline Length ◽  
Carrier Phase Measurement ◽  
Basic Model ◽  
Aircraft Type ◽  
Gps System

Recently, the SUAV has become the research focus at home and abroad. There is a new aircraft type: double ducted tilting Subminiature UAV system, this paper put forward a new attitude navigation system:AHRS-based low-cost GPS carrier phase orientation Navigation System. AHRS aids GPS fastly fix the attitude.This article proposed application the constraint solving the ambiguity basic model, which is based on the double differential equations of the carrier phase measurement. Then we use baseline length and the inaccurate attitude angle constraint to solver integer ambiguity. By the static experimental results show that this method is fast, effective, the AHRS-GPS system can provide high accuracy navigation for SUAV.

scholarly journals Improving DGNSS Performance through the Use of Network RTK Corrections

2021 ◽  
Vol 13 (9) ◽  
pp. 1621
Author(s):  
Duojie Weng ◽  
Shengyue Ji ◽  
Yangwei Lu ◽  
Wu Chen ◽  
Zhihua Li
Keyword(s):  
Carrier Phase ◽  
Local Area ◽  
Satellite System ◽  
High Accuracy ◽  
Single Frequency ◽  
Baseline Length ◽  
Low Latitude ◽  
Phase Measurements ◽  
Network Rtk ◽  
Global Navigation Satellite

The differential global navigation satellite system (DGNSS) is an enhancement system that is widely used to improve the accuracy of single-frequency receivers. However, distance-dependent errors are not considered in conventional DGNSS, and DGNSS accuracy decreases when baseline length increases. In network real-time kinematic (RTK) positioning, distance-dependent errors are accurately modelled to enable ambiguity resolution on the user side, and standard Radio Technical Commission for Maritime Services (RTCM) formats have also been developed to describe the spatial characteristics of distance-dependent errors. However, the network RTK service was mainly developed for carrier-phase measurements on professional user receivers. The purpose of this study was to modify the local-area DGNSS through the use of network RTK corrections. Distance-dependent errors can be reduced, and accuracy for a longer baseline length can be improved. The results in the low-latitude areas showed that the accuracy of the modified DGNSS could be improved by more than 50% for a 17.9 km baseline during solar active years. The method in this paper extends the use of available network RTK corrections with high accuracy to normal local-area DGNSS applications.

scholarly journals Effect of Nonlinear Baseline Length Constraint on Global Navigation Satellite System Compass: A Theoretical Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Yanlong Chen ◽  
Jincheng Fan ◽  
Guobin Chang ◽  
Siyu Zhang
Keyword(s):  
Global Navigation Satellite System ◽  
Low Cost ◽  
Satellite System ◽  
Baseline Length ◽  
Navigation Satellite ◽  
Angle Estimation ◽  
Length Constraint ◽  
Simple Scaling ◽  
Global Navigation ◽  
Global Navigation Satellite

GNSS (global navigation satellite system) compass is a low-cost, high-precision, and temporally stable north-finding technique. While the nonlinear baseline length constraint is widely known to be important in ambiguity resolution of GNSS compass, its direct effect on yaw angle estimation is theoretically analyzed in this work. Four different methods are considered with different ways in which the length constraint is made use of as follows: one without considering the constraints, one with simple scaling, one with indirect statistical scaling, and one with direct statistical scaling. It is found that simple scaling does not have any effect on yaw estimation; indirect and direct statistical scalings are equivalent to each other with both being able to increase the precision. The analysis and the conclusion developed in this work can go in parallel for the case of the tilt angle estimation.

scholarly journals An Advanced Multipath Mitigation Method Based on Trend Surface Analysis

2020 ◽  
Vol 12 (21) ◽  
pp. 3601
Author(s):  
Zhiren Wang ◽  
Wen Chen ◽  
Danan Dong ◽  
Chenglong Zhang ◽  
Yu Peng ◽  
...  
Keyword(s):  
Surface Analysis ◽  
Low Cost ◽  
Correction Method ◽  
Satellite System ◽  
Double Difference ◽  
Trend Surface Analysis ◽  
Multipath Mitigation ◽  
Trend Surface ◽  
Noise Interference ◽  
Grid Points

Among various ways to eliminate the multipath effect in high-precision global navigation satellite system positioning, the multipath hemispherical map (MHM) is a typical multipath correction method based on spatial domain repeatability, which is suitable for not only static environments, but also some dynamic carriers, such as ships and aircraft. So, it has notable advantages and is widely used. The MHM method divides the sky into grids according to the azimuth and elevation angles of satellite, and calculates the average of the residuals within the grid points as its multipath calibration value. It is easy to implement, but it will inevitably lead to excessive or insufficient multipath correction in the grid. The trend surface analysis-based multipath hemispherical map (T-MHM) method makes up for this deficiency by performing trend surface analysis on the multipath spatial changes within the grid points. However, the effectiveness of T-MHM is limited and less capable of resisting noise interference due to the multicollinearity between the independent variables caused by the special spatial distribution of multipath sampling and the overfitting problem caused by ignoring the multipath anisotropy. Thus, we proposed an improved multipath elimination method named AT-MHM (advanced trend surface analysis-based multipath hemispherical model), which cautiously judges the occurrence of the above problems and gives corresponding solutions. This was extended to double-difference mode, which expands the scope of application. The performance of AT-MHM in GPS pseudorange multipath mitigation was verified on geodetic receiver and low-cost receiver in a strong multipath environment with high occlusion.

scholarly journals Characterisation of GNSS Carrier Phase Data on a Moving Zero-Baseline in Urban and Aerial Navigation

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4046 ◽  
Author(s):  
Fabian Ruwisch ◽  
Ankit Jain ◽  
Steffen Schön
Keyword(s):  
Global Navigation Satellite System ◽  
Carrier Phase ◽  
High Sensitivity ◽  
Satellite System ◽  
Double Difference ◽  
Navigation Satellite ◽  
Noise Levels ◽  
Global Navigation ◽  
Zero Baseline ◽  
Global Navigation Satellite

We present analyses of Global Navigation Satellite System (GNSS) carrier phase observations in multiple kinematic scenarios for different receiver types. Multi-GNSS observations are recorded on high sensitivity and geodetic-grade receivers operating on a moving zero-baseline by conducting terrestrial urban and aerial flight experiments. The captured data is post-processed; carrier phase residuals are computed using the double difference (DD) concept. The estimated noise levels of carrier phases are analysed with respect to different parameters. We find DD noise levels for L1 carrier phase observations in the range of 1.4–2 mm (GPS, Global Positioning System), 2.8–4.6 mm (GLONASS, Global Navigation Satellite System), and 1.5–1.7 mm (Galileo) for geodetic receiver pairs. The noise level for high sensitivity receivers is at least higher by a factor of 2. For satellites elevating above 30 ∘ , the dominant noise process is white phase noise. For the flight experiment, the elevation dependency of the noise is well described by the exponential model, while for the terrestrial urban experiment, multipath and diffraction effects overlay; hence no elevation dependency is found. For both experiments, a carrier-to-noise density ratio (C/N 0 ) dependency for carrier phase DDs of GPS and Galileo is clearly visible with geodetic-grade receivers. In addition, C/N 0 dependency is also visible for carrier phase DDs of GLONASS with geodetic-grade receivers for the terrestrial urban experiment.

Blind Deconvolution for Two-Thermocouple Sensor Characterization

2006 ◽  
Vol 129 (2) ◽  
pp. 194-202 ◽  
Author(s):  
Peter C. Hung ◽  
Robert J. Kee ◽  
George W. Irwin ◽  
Seán F. McLoone
Keyword(s):  
High Frequency ◽  
Blind Deconvolution ◽  
Low Cost ◽  
A Priori ◽  
Harsh Environment ◽  
Test Rig ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Automotive Engine ◽  
Algorithmic Compensation

Thermocouples are one of the most popular devices for temperature measurement due to their robustness, ease of manufacture and installation, and low cost. However, when used in the harsh environment found in combustion systems and automotive engine exhausts, large wire diameters are required and consequently the measurement bandwidth is reduced. This paper describes two new algorithmic compensation techniques based on blind deconvolution to address this loss of high-frequency signal components using the measurements from two thermocouples. In particular, a continuous-time approach is proposed, combined with a cross-relation blind deconvolution for parameter estimation. A feature of this approach is that no a priori assumption is made about the time constant ratio of the two thermocouples. The advantages, including small estimation variance and limitations of the method, are highlighted using results from simulation and test rig studies.

Carrier Phase GPS Navigation to the North Pole

1999 ◽  
Vol 52 (1) ◽  
pp. 80-89 ◽  
Author(s):  
T. Moore ◽  
G. W. Roberts
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Integer Ambiguity Resolution ◽  
North Pole ◽  
Integer Ambiguity ◽  
Reference Station ◽  
Baseline Length ◽  
Cycle Slips ◽  
The North ◽  
Long Baseline

Over the last few years, on-the-fly integer ambiguity resolution for GPS has proven to be successful over short baselines (<20 km). However, the remaining challenge has been to extend the length of the baseline between the reference station and the mobile receiver, whilst still maintaining the capability of on-the-fly resolution and true carrier-based kinematic positioning. The goal has been to achieve centimetric level positioning at ranges of over 500 km. New techniques have been developed at the University of Nottingham to allow very long baseline integer ambiguity resolution, on-the-fly. A major problem with the use of carrier phase data is that posed by cycle slips. A technique for detecting and correcting cycle slips has been developed, and its use is discussed in this paper. The new technique has been proven through a series of trials, one of which included two flights to the North Pole, performing centimetric level positioning all the way to the pole. For many years, the GD Aero-Systems Course of the Air Warfare Centre based at RAF Cranwell executed a series of equipment flight trials to the North Pole, called the ARIES Flights. In May 1996, the authors were fortunate to take part in both flights, via Iceland and Greenland, to the North Pole. Based on reference stations at Thule Air Base, integer ambiguity resolution was accomplished, on-the-fly, and centimetric level navigation maintained throughout the flights. Earlier trials detailed in the paper demonstrate that the technique can resolve integer ambiguities on-the-fly within a few seconds over a baseline length of approximately 134 km, resulting in an accuracy of 12 cm. The majority of the residual error source for this being the ionosphere.

Influencing Factors of GNSS Differential Inter-System Bias and Performance Assessment of Tightly Combined GPS, Galileo, and QZSS Relative Positioning for Short Baseline

2018 ◽  
Vol 72 (04) ◽  
pp. 965-986 ◽  
Author(s):  
Mingkui Wu ◽  
Xiaohong Zhang ◽  
Wanke Liu ◽  
Renpan Wu ◽  
Renlan Zhang ◽  
...  
Keyword(s):  
Success Rate ◽  
Influencing Factors ◽  
A Priori ◽  
Satellite System ◽  
Single Frequency ◽  
Relative Positioning ◽  
Combined Model ◽  
Short Baseline ◽  
System Bias ◽  
The Impact

This paper first investigates the influencing factors of between-receiver Differential Inter-System Bias (DISB) between overlapping frequencies of the Global Positioning System (GPS), Galileo and the Quasi-Zenith Satellite System (QZSS). It was found that the receiver reboot and the type of observations may have an impact on DISBs. The impact of receiver firmware upgrades and the activation of anti-multipath filters are also investigated and some new results are presented. Then a performance evaluation is presented of tightly combined relative positioning for a short baseline with GPS/Galileo/QZSS L1-E1-L1/L5-E5a-L5 observations with the current constellations, in which the recently launched Galileo and QZSS satellites will also be included. It is demonstrated that when DISBs are a priori calibrated and corrected, the tightly combined model can deliver a much higher empirical ambiguity resolution success rate and positioning accuracy with respect to the classical loosely combined model, especially under environments where the observed satellites for each system are limited and only single-frequency observations are available. The ambiguity dilution of precision, bootstrapping success rate, and ratio values are analysed to illustrate the benefits of the tightly combined model as well.

scholarly journals An Innovative Fingerprint Location Algorithm for Indoor Positioning Based on Array Pseudolite

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4420 ◽  
Author(s):  
Lu Huang ◽  
Xingli Gan ◽  
Baoguo Yu ◽  
Heng Zhang ◽  
Shuang Li ◽  
...  
Keyword(s):  
Carrier Phase ◽  
Indoor Environment ◽  
Satellite System ◽  
Indoor Positioning ◽  
Integer Ambiguity ◽  
Positioning System ◽  
Indoor Environments ◽  
Positioning Accuracy ◽  
Static Conditions ◽  
Fingerprint Database

Since the signals of the global navigation satellite system (GNSS) are blocked by buildings, accurate positioning cannot be achieved in an indoor environment. Pseudolite can simulate similar outdoor satellite signals and can be used as a stable and reliable positioning signal source in indoor environments. Therefore, it has been proposed as a good substitute and has become a research hotspot in the field of indoor positioning. There are still some problems in the pseudolite positioning field, such as: Integer ambiguity of carrier phase, initial position determination, and low signal coverage. To avoid the limitation of these factors, an indoor positioning system based on fingerprint database matching of homologous array pseudolite is proposed in this paper, which can achieve higher positioning accuracy. The realization of this positioning system mainly includes the offline phase and the online phase. In the offline phase, the carrier phase data in the indoor environment is first collected, and a fingerprint database is established. Then a variational auto-encoding (VAE) network with location information is used to learn the probability distribution characteristics of the carrier phase difference of pseudolite in the latent space to realize feature clustering. Finally, the deep neural network is constructed by using the hidden features learned to further study the mapping relationship between different carrier phases of pseudolite and different indoor locations. In the online phase, the trained model and real-time carrier phases of pseudolite are used to predict the location of the positioning terminal. In this paper, by a large number of experiments, the performance of the pseudolite positioning system is evaluated under dynamic and static conditions. The effectiveness of the algorithm is evaluated by the comparison experiments, the experimental results show that the average positioning accuracy of the positioning system in a real indoor scene is 0.39 m, and the 95% positioning error is less than 0.85 m, which outperforms the traditional fingerprint positioning algorithms.

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