The Analysis of Solar Storms’ Influence on GPS Measurement Errors

2014 ◽  
Vol 568-570 ◽  
pp. 90-95
Author(s):  
Li Ying Cao ◽  
Gui Wen Lan
Keyword(s):  
Measurement Errors ◽  
Measurement Precision ◽  
Observation Data ◽  
Dual Frequency ◽  
Gps Measurement ◽  
Gps Observation ◽  
Solar Storms ◽  
Frequency Observation ◽  
Observation Period ◽  
Made In

This paper mainly analyzes the effects of solar storms on GPS measurement errors. Solar storms produce a lot of charged particles, which makes the electron density in ionosphere increase, and in further affects the ionosphere delay errors. Ionosphere delay errors are one of the main sources of GPS measurement error, which is a direct impact on measurement precision of GPS. GPS distance errors are caused by ionosphere delay errors. In the case of solar storms, dual frequency observation cannot completely remove ionosphere delay, so in measurement process appropriate methods will be used to reduce errors in GPS measurement, for example, during the observation in the night and increased observation period. By comparing and analyzing the GPS observation data in solar storms and under normal conditions with GAMIT/GLOBK software, a conclusion is made in this paper that observing in the night and the increased observation period can reduce the GPS measurement errors.

scholarly journals Accuracy Analysis of International Reference Ionosphere 2016 and NeQuick2 in the Antarctic

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1551
Author(s):  
Zihuai Guo ◽  
Yibin Yao ◽  
Jian Kong ◽  
Gang Chen ◽  
Chen Zhou ◽  
...  
Keyword(s):  
Solar Radiation ◽  
International Reference Ionosphere ◽  
Electron Content ◽  
Observation Data ◽  
Dual Frequency ◽  
Total Electron ◽  
International Reference ◽  
Antarctic Continent ◽  
The Antarctic ◽  
Frequency Observation

Global navigation satellite system (GNSS) can provide dual-frequency observation data, which can be used to effectively calculate total electron content (TEC). Numerical studies have utilized GNSS-derived TEC to evaluate the accuracy of ionospheric empirical models, such as the International Reference Ionosphere model (IRI) and the NeQuick model. However, most studies have evaluated vertical TEC rather than slant TEC (STEC), which resulted in the introduction of projection error. Furthermore, since there are few GNSS observation stations available in the Antarctic region and most are concentrated in the Antarctic continent edge, it is difficult to evaluate modeling accuracy within the entire Antarctic range. Considering these problems, in this study, GNSS STEC was calculated using dual-frequency observation data from stations that almost covered the Antarctic continent. By comparison with GNSS STEC, the accuracy of IRI-2016 and NeQuick2 at different latitudes and different solar radiation was evaluated during 2016–2017. The numerical results showed the following. (1) Both IRI-2016 and NeQuick2 underestimated the STEC. Since IRI-2016 utilizes new models to represent the F2-peak height (hmF2) directly, the IRI-2016 STEC is closer to GNSS STEC than NeQuick2. This conclusion was also confirmed by the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) occultation data. (2) The differences in STEC of the two models are both normally distributed, and the NeQuick2 STEC is systematically biased as solar radiation increases. (3) The root mean square error (RMSE) of the IRI-2016 STEC is smaller than that of the NeQuick2 model, and the RMSE of the two modeling STEC increases with solar radiation intensity. Since IRI-2016 relies on new hmF2 models, it is more stable than NeQuick2.

scholarly journals Analisis Total Electron Content (TEC) Menggunakan Continous Wavelet Transform Sebagai Indikator Prekursor Gempa Bumi Di Wilayah Provinsi Bengkulu

2019 ◽  
Vol 9 (2) ◽  
pp. 27-33
Author(s):  
Laksamana Agung Aprillo ◽  
Hendy Santosa ◽  
Faisal Hadi
Keyword(s):  
Wavelet Transform ◽  
Standard Deviation ◽  
Total Electron Content ◽  
Electromagnetic Waves ◽  
Electron Content ◽  
Observation Data ◽  
Dual Frequency ◽  
Total Electron ◽  
Gps Observation ◽  
Large Earthquakes

ABSTRACT Bengkulu is one of 34 provinces in Indonesia which is a megathrust region. So Bengkulu province is often hit by many large earthquakes with shallow depth. TEC anomaly was analyzed based on three electromagnetic waves radiated by an earthquake. The total electron content (TEC) anomaly is seen through the global positioning system (GPS) dual-frequency radio signal data. The continuous wavelet transform (CWT) method is used to divide the signal analysis into several sections according to the electromagnetic wave frequency range of acoustic (2.5 mHz) -3 mHz), gravity waves (1 mHz-2.8 mHz) and rayleigh waves (5 mHz-33 mHz). GPS observation data for 9 days is calculated using the Standard deviation (2?) method to see trends in data changes. The analysis shows anomalies in the September 12 2007 earthquake (7.9 Mw), the March 5 2010 earthquake (6.3 Mw) and the August 4 2011 earthquake (6.0 Mw). Anomalies are detected 1 to 5 hours before an earthquake occurs. TEC anomalies that occur may be related to the process of preseismic before the earthquake and may be an early sign of an earthquake.Keyword: earthquake, total electron content, continous wavelet transform, standard deviation

scholarly journals Current state and tendencies of distribution of ground frosts within the territory of Ukraine

2017 ◽  
pp. 37-42
Author(s):  
S. V. Klok
Keyword(s):  
Temperature Field ◽  
Air Temperature ◽  
Extreme Values ◽  
Negative Impact ◽  
Observation Data ◽  
Current State ◽  
Weather Phenomenon ◽  
Minimum Air Temperature ◽  
Observation Period ◽  
Made In

The purpose of this work consists in identifying the main trends of present-day formation and distribution of ground frosts throughout Ukraine. For this purpose the analysis of a minimum air temperature field has been conducted based on observation data at 186 stations of Ukraine for the period from 1991 to 2014. It is known that extreme values of air temperature are much more informative than its average values. Therefore analyses of meteorological extreme values usually lead to more substantial and qualitative results. In the course of the work, occurrences of frost in April, May and September have been studied separately from each other while these three months are deemed to be the most dangerous in terms of frosts' frequency and negative impact. In order to identify trends to occurrence of this dangerous weather phenomenon a comparison of two decades of 1991-2000 and 2001-2010 has been made. In addition, the latest observation period of 2011-2014 has been considered separately taking into account the results of comparative analysis of two preceding decades. The results of the work indicate a decrease of number of September days having this dangerous weather phenomenon during the last few years. However, recurrence of frosts remains stably high in April while in May it appears to be high only in certain years. The obtained results also indicate the fact that the northern and northeastern territories of Ukraine appear to be the most vulnerable to frosts. Thus it should be noted that a threat of adverse consequences caused by ground frosts is still there and remains to be quite high, especially for agriculture.

scholarly journals Establishment of European Regional Ionosphere Model Based on Spherical Harmonic Functions

2021 ◽  
Vol 5 (6) ◽  
pp. 5-9
Author(s):  
Mingze Zhang
Keyword(s):  
Spherical Harmonic ◽  
Observation Data ◽  
Test Results ◽  
Dual Frequency ◽  
Ionosphere Model ◽  
Variation Characteristics ◽  
Temporal And Spatial ◽  
Gps System ◽  
Frequency Observation ◽  
European Regional

In order to study the temporal and spatial variation characteristics of the regional ionosphere and the modeling accuracy, the experiment is based on the spherical harmonic function model, using the GPS, Glonass, and Galileo dual-frequency observation data from the 305th-334th day of the European CORS network in 2019 to establish a global ionospheric model. By analyzing and evaluating the accuracy of the global ionospheric puncture points, VTEC, and comparing code products, the test results showed that the GPS system has the most dense puncture electricity distribution, the Glonass system is the second, and the Galileo system is the weakest. The values of ionospheric VTEC calculated by GPS, Glonass and Galileo are slightly different, but in terms of trends, they are the same as those of ESA, JPL and UPC. GPS data has the highest accuracy in global ionospheric modeling. GPS, Glonass and Galileo have the same trend, but Glonass data is unstable and fluctuates greatly.

scholarly journals Modeling and Performance Evaluation of Precise Positioning and Time-Frequency Transfer with Galileo Five-Frequency Observations

2021 ◽  
Vol 13 (15) ◽  
pp. 2972
Author(s):  
Wei Xu ◽  
Wen-Bin Shen ◽  
Cheng-Hui Cai ◽  
Li-Hong Li ◽  
Lei Wang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Satellite Orbit ◽  
Average Frequency ◽  
Satellite System ◽  
Observation Data ◽  
Navigation Satellite ◽  
Dual Frequency ◽  
Time Frequency ◽  
Combination Model ◽  
Frequency Transfer

The present Global Navigation Satellite System (GNSS) can provide at least double-frequency observations, and especially the Galileo Navigation Satellite System (Galileo) can provide five-frequency observations for all constellation satellites. In this contribution, precision point positioning (PPP) models with Galileo E1, E5a, E5b, E5 and E6 frequency observations are established, including a dual-frequency (DF) ionospheric-free (IF) combination model, triple-frequency (TF) IF combination model, quad-frequency (QF) IF combination model, four five-frequency (FF) IF com-bination models and an FF uncombined (UC) model. The observation data of five stations for seven days are selected from the multi-GNSS experiment (MGEX) network, forming four time-frequency links ranging from 454.6 km to 5991.2 km. The positioning and time-frequency transfer performances of Galileo multi-frequency PPP are compared and evaluated using GBM (which denotes precise satellite orbit and clock bias products provided by Geo Forschung Zentrum (GFZ)), WUM (which denotes precise satellite orbit and clock bias products provided by Wuhan University (WHU)) and GRG (which denotes precise satellite orbit and clock bias products provided by the Centre National d’Etudes Spatiales (CNES)) precise products. The results show that the performances of the DF, TF, QF and FF PPP models are basically the same, the frequency stabilities of most links can reach sub10−16 level at 120,000 s, and the average three-dimensional (3D) root mean square (RMS) of position and average frequency stability (120,000 s) can reach 1.82 cm and 1.18 × 10−15, respectively. The differences of 3D RMS among all models are within 0.17 cm, and the differences in frequency stabilities (in 120,000 s) among all models are within 0.08 × 10−15. Using the GRG precise product, the solution performance is slightly better than that of the GBM or WUM precise product, the average 3D RMS values obtained using the WUM and GRG precise products are 1.85 cm and 1.77 cm, respectively, and the average frequency stabilities at 120,000 s can reach 1.13 × 10−15 and 1.06 × 10−15, respectively.

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.

Is Self-Confidence a Bias Factor in Higher-Order Catastrophe Models? An Exploratory Analysis—A Critique

2005 ◽  
Vol 27 (3) ◽  
pp. 375-381 ◽  
Author(s):  
Gershon Tenenbaum ◽  
Betsy Becker
Keyword(s):  
Repeated Measures ◽  
Measurement Errors ◽  
Quadrant Analysis ◽  
Continuous Variables ◽  
Self Confidence ◽  
Cognitive Anxiety ◽  
Bias Factor ◽  
Repeated Measures Analysis ◽  
Catastrophe Models ◽  
Made In

The current paper criticizes the concept, research methodology, data analyses, and validity of the conclusions made in Hardy, Woodman, and Carrington’s (2004) article published in this journal. In their repeated-measures analysis of data from the performances of 7 golfers, they did not examine changes in performance scores on successive holes. Instead, Hardy et al. used several ANOVA models to examine how performance varied with respect to somatic and cognitive anxiety level and self-confidence interaction. By doing so, their findings produced effects which we argue to be conceptually and empirically limited. We also address problems associated with dichotomization of continuous variables, measurement errors when splitting data, eradication of random significant effects, cell sizes in segmental quadrant analysis, and correlation between somatic and cognitive anxiety. We believe these difficulties prevent any reliable conclusions and/or generalizations from being made.

scholarly journals Positioning Evaluation of Single and Dual-Frequency Low-Cost GNSS Receivers Signals Using PPP and Static Relative Methods in Urban Areas

2021 ◽  
Vol 11 (22) ◽  
pp. 10642
Author(s):  
Rosendo Romero-Andrade ◽  
Manuel E. Trejo-Soto ◽  
Alejandro Vega-Ayala ◽  
Daniel Hernández-Andrade ◽  
Jesús R. Vázquez-Ontiveros ◽  
...  
Keyword(s):  
Urban Areas ◽  
Precise Point Positioning ◽  
Low Cost ◽  
Observation Data ◽  
Dual Frequency ◽  
Positional Accuracy ◽  
Gnss Receivers ◽  
Point Positioning ◽  
Error Circle ◽  
Vertical Positioning

A positional accuracy obtained by the Precise Point Positioning and static relative methods was compared and analyzed. Test data was collected using low-cost GNSS receivers of single- and dual-frequency in urban areas. The data was analyzed for quality using the TEQC program to determine the degree of affectation of the signal in the urban area. Low-cost GNSS receivers were found to be sensitive to the multipath effect, which impacts positioning. The horizontal and vertical accuracy was evaluated with respect to Mexican regulations for the GNSS establishment criteria. Probable Error Circle (CEP) and Vertical Positioning Accuracy (EPV) were performed on low cost GNSS receiver observation data. The results show that low-cost dual-frequency GNSS receivers can be used in urban areas. The precision was obtained in the order of 0.013 m in the static relative method. The results obtained are comparable to a geodetic receiver in a geodetic baseline of <20 km. The study does not recommend using single and dual frequencies low cost GNSS receivers based on results obtained by the Precise Point Positioning (PPP) method in urban areas. The inclusion of the GGM10 model reduces the vertical precision obtained by using low cost GNSS receivers in both methods, conforming to the regulations only in the horizontal component.

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