scholarly journals Application of IGS Products for Air Navigation

2017 ◽  
Vol 24 (1) ◽  
pp. 285-300
Author(s):  
Henryk Jafernik ◽  
Janusz Ćwiklak ◽  
Kamil Krasuski ◽  
Jarosław Kozuba
Keyword(s):  
Least Squares Method ◽  
Single Point ◽  
Mean Value ◽  
Dual Frequency ◽  
Static Mode ◽  
Precise Positioning ◽  
Gps Satellites ◽  
Precise Ephemeris ◽  
Method Accuracy ◽  
Gps Observations

Abstract Single Point Positioning (SPP) method is widely used in air, marine, and land navigation to determine the user’s position in real time and post factum. A typical accuracy for this method of determining the user’s position in the static mode is approximately 10 meters. In air operations, the SPP method accuracy can be several times lower and that may cause problems with precise positioning of an aircraft. The authors of this article presented preliminary results of research concerning aircraft positioning in the kinematic mode based on GPS observations. For this purpose, an in-flight experiment, in which a Cessna 172 aircraft was used, was performed at the airport in Mielec, Poland. The aircraft was equipped with a dual-frequency Topcon TPS HiperPro receiver, which was recording satellite observations with 1-second interval. The aircraft position was determined using the least-squares method (LSM) in the RTKLIB (RTKPOST module) software. Two research tests were performed within the scope of the experiment, i.e. in test I the aircraft position was determined on the basis of raw GPS observations and the broadcast ephemeris data whereas in test II precision products of the IGS were used, such as: precise ephemeris SP3, DCB hardware delay, clock bias data of GPS satellites and receivers in the CLK format, data of the ionosphere maps based on IONEX format, and phase center calibration of GPS satellites and receivers in the ANTEX format. The use of the IGS precision products improved the accuracy of the X coordinate to 1 m, Y to 0.7 m and Z to 1.3 m. On the basis of tests I and II, an additional RMS-3D parameter was determined, whose mean value was 4 m.

scholarly journals Calibration of BeiDou Triple-Frequency Receiver-Related Pseudorange Biases and Their Application in BDS Precise Positioning and Ambiguity Resolution

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3500 ◽  
Author(s):  
Fu Zheng ◽  
Xiaopeng Gong ◽  
Yidong Lou ◽  
Shengfeng Gu ◽  
Guifei Jing ◽  
...  
Keyword(s):  
Ambiguity Resolution ◽  
Single Point ◽  
Satellite System ◽  
Single Frequency ◽  
Navigation Satellite ◽  
Dual Frequency ◽  
Precise Positioning ◽  
Triple Frequency ◽  
Wide Lane ◽  
Point Positioning

Global Navigation Satellite System pseudorange biases are of great importance for precise positioning, timing and ionospheric modeling. The existence of BeiDou Navigation Satellite System (BDS) receiver-related pseudorange biases will lead to the loss of precision in the BDS satellite clock, differential code bias estimation, and other precise applications, especially when inhomogeneous receivers are used. In order to improve the performance of BDS precise applications, two ionosphere-free and geometry-free combinations and ionosphere-free pseudorange residuals are proposed to calibrate the raw receiver-related pseudorange biases of BDS on each frequency. Then, the BDS triple-frequency receiver-related pseudorange biases of seven different manufacturers and twelve receiver models are calibrated. Finally, the effects of receiver-related pseudorange bias are analyzed by BDS single-frequency single point positioning (SPP), single- and dual-frequency precise point positioning (PPP), wide-lane uncalibrated phase delay (UPD) estimation, and ambiguity resolution, respectively. The results show that the BDS SPP performance can be significantly improved by correcting the receiver-related pseudorange biases and the accuracy improvement is about 20% on average. Moreover, the accuracy of single- and dual-frequency PPP is improved mainly due to a faster convergence when the receiver-related pseudorange biases are corrected. On the other hand, the consistency of wide-lane UPD among different stations is improved significantly and the standard deviation of wide-lane UPD residuals is decreased from 0.195 to 0.061 cycles. The average success rate of wide-lane ambiguity resolution is improved about 42.10%.

scholarly journals Conditioning and PPP processing of smartphone GNSS measurements in realistic environments

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Ganga Shinghal ◽  
Sunil Bisnath
Keyword(s):  
Single Point ◽  
A Priori ◽  
Density Ratio ◽  
Satellite System ◽  
Quality Parameters ◽  
Urban Environments ◽  
Dual Frequency ◽  
Missing Measurements ◽  
Data Gaps ◽  
Point Positioning

AbstractSmartphones typically compute position using duty-cycled Global Navigation Satellite System (GNSS) L1 code measurements and Single Point Positioning (SPP) processing with the aid of cellular and other measurements. This internal positioning solution has an accuracy of several tens to hundreds of meters in realistic environments (handheld, vehicle dashboard, suburban, urban forested, etc.). With the advent of multi-constellation, dual-frequency GNSS chips in smartphones, along with the ability to extract raw code and carrier-phase measurements, it is possible to use Precise Point Positioning (PPP) to improve positioning without any additional equipment. This research analyses GNSS measurement quality parameters from a Xiaomi MI 8 dual-frequency smartphone in varied, realistic environments. In such environments, the system suffers from frequent phase loss-of-lock leading to data gaps. The smartphone measurements have low and irregular carrier-to-noise (C/N0) density ratio and high multipath, which leads to poor or no positioning solution. These problems are addressed by implementing a prediction technique for data gaps and a C/N0-based stochastic model for assigning realistic a priori weights to the observables in the PPP processing engine. Using these conditioning techniques, there is a 64% decrease in the horizontal positioning Root Mean Square (RMS) error and 100% positioning solution availability in sub-urban environments tested. The horizontal and 3D RMS were 20 cm and 30 cm respectively in a static open-sky environment and the horizontal RMS for the realistic kinematic scenario was 7 m with the phone on the dashboard of the car, using the SwiftNav Piksi Real-Time Kinematic (RTK) solution as reference. The PPP solution, computed using the YorkU PPP engine, also had a 5–10% percentage point more availability than the RTK solution, computed using RTKLIB software, since missing measurements in the logged file cause epoch rejection and a non-continuous solution, a problem which is solved by prediction for the PPP solution. The internal unaided positioning solution of the phone obtained from the logged NMEA (The National Marine Electronics Association) file was computed using point positioning with the aid of measurements from internal sensors. The PPP solution was 80% more accurate than the internal solution which had periodic drifts due to non-continuous computation of solution.

scholarly journals Real-time GNSS precise point positioning for low-cost smart devices

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Liang Wang ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Zhiyu Wang
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Precise Point Positioning ◽  
Low Cost ◽  
Smart Devices ◽  
Dual Frequency ◽  
Static Mode ◽  
Phase Measurements ◽  
Positioning Errors ◽  
Point Positioning

AbstractGlobal Navigation Satellite System raw measurements from Android smart devices make accurate positioning possible with advanced techniques, e.g., precise point positioning (PPP). To achieve the sub-meter-level positioning accuracy with low-cost smart devices, the PPP algorithm developed for geodetic receivers is adapted and an approach named Smart-PPP is proposed in this contribution. In Smart-PPP, the uncombined PPP model is applied for the unified processing of single- and dual-frequency measurements from tracked satellites. The receiver clock terms are parameterized independently for the code and carrier phase measurements of each tracking signal for handling the inconsistency between the code and carrier phases measured by smart devices. The ionospheric pseudo-observations are adopted to provide absolute constraints on the estimation of slant ionospheric delays and to strengthen the uncombined PPP model. A modified stochastic model is employed to weight code and carrier phase measurements by considering the high correlation between the measurement errors and the signal strengths for smart devices. Additionally, an application software based on the Android platform is developed for realizing Smart-PPP in smart devices. The positioning performance of Smart-PPP is validated in both static and kinematic cases. Results show that the positioning errors of Smart-PPP solutions can converge to below 1.0 m within a few minutes in static mode and the converged solutions can achieve an accuracy of about 0.2 m of root mean square (RMS) both for the east, north and up components. For the kinematic test, the RMS values of Smart-PPP positioning errors are 0.65, 0.54 and 1.09 m in the east, north and up components, respectively. Static and kinematic tests both show that the Smart-PPP solutions outperform the internal results provided by the experimental smart devices.

scholarly journals Precise Point Positioning Using Dual-Frequency GNSS Observations on Smartphone

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2189 ◽  
Author(s):  
Qiong Wu ◽  
Mengfei Sun ◽  
Changjie Zhou ◽  
Peng Zhang
Keyword(s):  
Precise Point Positioning ◽  
Frequency Mode ◽  
Single Frequency ◽  
Dual Frequency ◽  
Static Mode ◽  
Position Errors ◽  
Point Positioning ◽  
Similar Accuracy ◽  
Positioning Algorithm ◽  
Gnss Observations

The update of the Android system and the emergence of the dual-frequency GNSS chips enable smartphones to acquire dual-frequency GNSS observations. In this paper, the GPS L1/L5 and Galileo E1/E5a dual-frequency PPP (precise point positioning) algorithm based on RTKLIB and GAMP was applied to analyze the positioning performance of the Xiaomi Mi 8 dual-frequency smartphone in static and kinematic modes. The results showed that in the static mode, the RMS position errors of the dual-frequency smartphone PPP solutions in the E, N, and U directions were 21.8 cm, 4.1 cm, and 11.0 cm, respectively, after convergence to 1 m within 102 min. The PPP of dual-frequency smartphone showed similar accuracy with geodetic receiver in single-frequency mode, while geodetic receiver in dual-frequency mode has higher accuracy. In the kinematic mode, the positioning track of the smartphone dual-frequency data had severe fluctuations, the positioning tracks derived from the smartphone and the geodetic receiver showed approximately difference of 3–5 m.

Multi-GNSS Single-Difference Baseline Processing at NGS with newly developed M-PAGES software

2021 ◽  
Author(s):  
Bryan Stressler ◽  
Andria Bilich ◽  
Clement Ogaja ◽  
Jacob Heck
Keyword(s):  
Geodetic Survey ◽  
Integer Ambiguity ◽  
National Geodetic Survey ◽  
Processing Strategy ◽  
Dual Frequency ◽  
Software Suite ◽  
Legacy Software ◽  
Double Differences ◽  
Single Difference ◽  
Gps Observations

<p>The U.S. National Geodetic Survey (NGS) has historically processed dual-frequency GPS observations in a double-differenced mode using the legacy software called the Program for the Adjustment of GPS Ephemerides (PAGES). As part of NGS’ modernization efforts, a new software suite named M-PAGES (i.e., Multi-GNSS PAGES) is being developed to replace PAGES. M-PAGES consists of a suite of C++ and Python libraries, programs, and scripts built to process observations from all GNSS constellations. The M-PAGES team has developed a single-difference baseline processing strategy that is suitable for multi-GNSS. This approach avoids the difficulty of forming double-differences across systems or frequencies, which may inhibit integer ambiguity resolution. The M-PAGES suite is expected to deploy to NGS’ Online Positioning User Service (OPUS) later this year. Here, we present the processing strategy being implemented along with a performance evaluation from sample baseline solutions obtained from data collected within the NOAA CORS Network.</p>

Kinetic equations of creep and damage for description of materials with non-monotonic dependence of fracture strain on stress

2021 ◽  
Vol 23 (3) ◽  
pp. 139-154
Author(s):  
Inna Banshchikova ◽  
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Fracture Strain ◽  
Least Squares Method ◽  
Kinetic Equations ◽  
Steel 12Kh18n10t ◽  
Static Mode ◽  
Creep Curves

Introduction. Reducing the level of damage accumulation during pressure treatment of materials at elevated temperatures in creep and close to superplasticity modes in the manufacture of parts can significantly increase its service life in the cold state. Finding temperature and power conditions leading to a reduction in damage of material during the production process and operation is an important task. The purposes of the work: 1) to show the possibility of using the Sosnin-Gorev creep and damage model for alloys with a non-monotonic dependence of strain at fracture on diagrams with creep curves; 2) to carry out comparative analysis of damage accumulation under conditions of uniaxial tension at constant stress and at constant strain rates for alloy with such a dependence. Research methods. Used scalar damage parameter is equated to the normalized deformation, i.e. to the ratio of the current strain to the fracture strain. To find the coefficients of relations creep and damage, the similarity of the creep curves in the normalized values “normalized strain – normalized time”, i.e. the presence of single normalized curve of damage accumulation is checked. The least squares method is used to approximate the experimental data. Numerical integration methods are used for comparative analysis of deformation modes. Results and discussion. Determination of the parameters of the creep and damage equations by the method of a single normalized curve is carried out on the example of experimental data for steel 12Kh18N10T (12Cr18Ni10Ti) at 850 °C, which has a minimum of fracture strain in diagrams with creep curves. Analysis of the static and kinematic modes of deformation for studied material showed that damage accumulation in both cases is practically the same for stresses close to the stress at which this minimum is reached. If the stresses are lower, then the lower level of damage accumulation will be in the kinematic mode; if the stresses above the minimum value, then the static mode will lead to a lower level of damage accumulation. Application. The obtained results can be useful when choosing rational modes of forming structural elements from alloys with a non-monotonic dependence of the fracture strain on stress, as well as in evaluating it for long-term strength during operation.

scholarly journals Kinematic ME-MAFA for Pseudolite Carrier-Phase Ambiguity Resolution in Precise Single-Point Positioning

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6197
Author(s):  
Kai Liu ◽  
Xiye Guo ◽  
Jun Yang ◽  
Xiaoyu Li ◽  
Changshui Liu ◽  
...  
Keyword(s):  
Success Rate ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Single Point ◽  
Heuristic Method ◽  
Voronoi Cell ◽  
Static Mode ◽  
Single Point Positioning ◽  
Cycle Slips ◽  
Point Positioning

Precise single-point positioning using carrier-phase measurements can be provided by the synchronized pseudolite system. The primary task of carrier phase positioning is ambiguity resolution (AR) with rapidity and reliability. As the pseudolite system is usually operated in the dense multipath environment, cycle slips may lead the conventional least-squares ambiguity decorrelation adjustment (LAMBDA) method to incorrect AR. A new AR method based on the idea of the modified ambiguity function approach (MAFA), which is insensitive to the cycle slips, is studied in this paper. To improve the model strength of the MAFA and to eliminate the influence of constant multipath biases on the time-average model in static mode, the kinematic multi-epoch MAFA (kinematic ME-MAFA) algorithm is proposed. A heuristic method for predicting the ‘float position’ corresponding to every Voronoi cell of the next epoch, making use of Doppler-based velocity information, is implemented to improve the computational efficiency. If the success rate is very close to 1, it is possible to guarantee reliable centimeter-level accuracy positioning without further ambiguity validation. Therefore, a computing method of the success rate for the kinematic ME-MAFA is proposed. Both the numerical simulations and the kinematic experiment demonstrate the feasibility of the new AR algorithm according to its accuracy and reliability. The accuracy of the horizontal positioning solution is better than 1.7 centimeters in our pseudolite system.

scholarly journals What Explains the Size of Sovereign Wealth Funds?

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Antonia Ficova ◽  
Juraj Sipko
Keyword(s):  
Inflation Rate ◽  
Least Squares Method ◽  
Mean Value ◽  
Balance Of Payments ◽  
Gdp Growth ◽  
Foreign Exchange Reserves ◽  
Sovereign Wealth Funds ◽  
The Public ◽  
Rate Of Growth ◽  
Rapid Appearance

Abstract Reasons for the rapid appearance and growth of SWFs is contributed by increase in oil prices and the accumulation of large balance-of-payments surpluses. Purpose of the article is to investigate size of observed Sovereign Wealth Funds in 2013. Moreover, to describe what explain differences in the size of SWFs, on the other hand what determines the amount of foreign exchange reserves. Is the size of observed funds closely related to rate of growth of the countries? Is return of observed funds is closely related to fund value bn USD, GDP growth (annual %) and inflation rate of the country? Methodology/methods deployed in this paper has been done illustrations by using available data from official websites of funds, Sovereign Wealth Fund Institute, International Monetary Fund, CIA The World Factbook and author’s calculations due the fact that most of funds do not provide data to the public. In addition to this, we present the estimations by using regression analysis, transferring observed data using the least squares method, The two-sample t-test for mean value, ANOVA, TINV. Scientific aim is to examine whether AUM of SWFs, moreover the size of 14 observed funds is closely related to rate of growth of the countries at 90 percent of probability. Second, if return of 14 observed funds is closely related to fund value bn USD, GDP growth (annual %) and inflation rate of the country at 95 percent of probability. Third, if there are significant differences between return in 2010 and 2013. Findings indicates that paper came to the conclusion that the return of 14 observed funds is closely related to fund value bn USD, GDP growth (annual %) and inflation rate of the country at 95 percent of probability. Furthermore, there are significant differences between return in 2010 and 2013. Conclusions (limits, implications etc) pointed out that the influence of SWFs has become undeniable, with total assets topping 6,585tn USD in June 2014, these investors have reached a size comparable to that of the entire alternative assets industry.

scholarly journals Feasibility of Using Low-Cost Dual-Frequency GNSS Receivers for Land Surveying

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 1956
Author(s):  
Natalia Wielgocka ◽  
Tomasz Hadas ◽  
Adrian Kaczmarek ◽  
Grzegorz Marut
Keyword(s):  
Real Time ◽  
Field Experiments ◽  
Low Cost ◽  
Base Station ◽  
Global Navigation Satellite Systems ◽  
Single Frequency ◽  
Signal Acquisition ◽  
Dual Frequency ◽  
Static Mode ◽  
Land Surveying

Global Navigation Satellite Systems (GNSS) have revolutionized land surveying, by determining position coordinates with centimeter-level accuracy in real-time or up to sub-millimeter accuracy in post-processing solutions. Although low-cost single-frequency receivers do not meet the accuracy requirements of many surveying applications, multi-frequency hardware is expected to overcome the major issues. Therefore, this paper is aimed at investigating the performance of a u-blox ZED-F9P receiver, connected to a u-blox ANN-MB-00-00 antenna, during multiple field experiments. Satisfactory signal acquisition was noticed but it resulted as >7 dB Hz weaker than with a geodetic-grade receiver, especially for low-elevation mask signals. In the static mode, the ambiguity fixing rate reaches 80%, and a horizontal accuracy of few centimeters was achieved during an hour-long session. Similar accuracy was achieved with the Precise Point Positioning (PPP) if a session is extended to at least 2.5 h. Real-Time Kinematic (RTK) and Network RTK measurements achieved a horizontal accuracy better than 5 cm and a sub-decimeter vertical accuracy. If a base station constituted by a low-cost receiver is used, the horizontal accuracy degrades by a factor of two and such a setup may lead to an inaccurate height determination under dynamic surveying conditions, e.g., rotating antenna of the mobile receiver.

Integration of Moving Least Squares Method and Multilevel B-Spline Method for Scattered Data Approximation

2011 ◽  
Vol 291-294 ◽  
pp. 2245-2249
Author(s):  
Shi Ju Yan ◽  
Bin Ge
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Scattered Data ◽  
Moving Least Squares ◽  
Scattered Data Approximation ◽  
Approximation Accuracy ◽  
Data Approximation ◽  
B Spline ◽  
Moving Least Squares Method ◽  
Method Accuracy

For scattered data approximation with multilevel B-spline(MBS) method, accuracy could be enhanced by densifying control lattice. Nevertheless, when control lattice density reaches to some extent, approximation accuracy could not be enhanced further. A strategy based on integration of moving least squares(MLS) and multilevel B-spline(MBS) is presented. Experimental results demonstrate that the presented strategy has higher approximation accuracy.

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