scholarly journals On Global Ionospheric Maps based winter-time GPS ionospheric delay with reference to the Klobuchar model

Pomorstvo ◽  
2019 ◽  
Vol 33 (2) ◽  
pp. 210-221
Author(s):  
David Brčić ◽  
Renato Filjar ◽  
Serdjo Kos ◽  
Marko Valčić
Keyword(s):  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Ground Truth Data ◽  
Local Pattern ◽  
Satellite Positioning ◽  
Klobuchar Model ◽  
Global Ionospheric Maps ◽  
Winter Time ◽  
Delay Correction

Modelling of the ionospheric Total Electron Content (TEC) represents a challenging and demanding task in Global Navigation Satellite Systems (GNSS) positioning performance. In terms of satellite Positioning, Navigation and Timing (PNT), TEC represents a significant cause of the satellite signal ionospheric delay. There are several approaches to TEC estimation. The Standard (Klobuchar) ionospheric delay correction model is the most common model for Global Positioning System (GPS) single-frequency (L1) receivers. The development of International GNSS Service (IGS) Global Ionospheric Maps (GIM) has enabled the insight into global TEC dynamics. GIM analyses in the Northern Adriatic area have shown that, under specific conditions, local ionospheric delay patterns differ from the one defined in the Klobuchar model. This has been the motivation for the presented research, with the aim to develop a rudimentary model of the TEC estimation, with emphasis on areas where ground truth data are not available. The local pattern of the ionospheric delay has been modelled with wave functions based on the similarity of waveforms, considering diurnal differences in TEC behavior from defined TEC patterns. The model represents a spatiotemporal winter-time ionospheric delay correction with the Klobuchar model as a basis. The evaluation results have shown accurate approximation of the local pattern of the ionospheric delay. The model was verified in the same seasonal period in 2007, revealing it successfulness under pre-defined conditions. The presented approach represents a basis for the further work on the local ionospheric delay modelling, considering local ionospheric and space weather conditions, thus improving the satellite positioning performance for single-frequency GNSS receivers.

Klobuchar-Like Local Model of Quiet Space Weather GPS Ionospheric Delay for Northern Adriatic

2009 ◽  
Vol 62 (3) ◽  
pp. 543-554 ◽  
Author(s):  
Renato Filjar ◽  
Tomislav Kos ◽  
Serdjo Kos
Keyword(s):  
Space Weather ◽  
Weather Conditions ◽  
Ionospheric Delay ◽  
Delay Model ◽  
Northern Adriatic ◽  
Positioning Systems ◽  
Research Activities ◽  
Satellite Positioning ◽  
Klobuchar Model ◽  
The Impact

Ionospheric delay is the major source of satellite positioning system performance degradation. Designers of satellite positioning systems attempt to mitigate the impact of the ionospheric delay by deployment of correction models. For instance, the American GPS utilises a global standard (Klobuchar) model, based on the assumption that the daily distribution of GPS ionospheric delay values follows a biased cosine curve during day-time, while during the night-time the GPS ionospheric delay remains constant. Providing a compromise between computational complexity and accuracy, the Klobuchar model is capable of correcting up to 70% of actual ionospheric delay, mainly during quiet space weather conditions. Unfortunately, it provides a very poor performance during severe space weather, geomagnetic and ionospheric disturbances. In addition, a global approach in Klobuchar model development did not take into account particularities of the local ionospheric conditions that can significantly contribute to the general GPS ionospheric delay. Current research activities worldwide are concentrating on a better understanding of the observed GPS ionospheric delay dynamics and the relation to local ionosphere conditions.Here we present the results of a study addressing daily GPS ionospheric delay dynamics observed at a Croatian coastal area of the northern Adriatic (position ϕ=45°N, λ=15°E) in the periods of quiet space weather in 2007. Daily sets of actual GPS ionospheric delay values were assumed to be the time series of composite signals, consisting of DC, cosine and residual components, respectively. Separate models have been developed that describe components of actual GPS ionospheric delay in the northern Adriatic for summer and winter, respectively. A special emphasis was given to the statistical description of the residual component of the daily distribution of GPS ionospheric delay, obtained by removing DC (bias) and cosine components from the composite GPS ionospheric delay.Future work will be focused on further evaluation and validation of a quiet space weather GPS ionospheric delay model for the northern Adriatic, transition to a non-Klobuchar model, and on research in local GPS ionospheric delay dynamics during disturbed and severe space weather conditions.

scholarly journals Long-term Performance Evaluation for Ionospheric Delay Correction of BeiDou Navigation Satellite System

2019 ◽  
Vol 131 ◽  
pp. 01075
Author(s):  
Chen Liu ◽  
Yi Jiang ◽  
Ye Chen ◽  
Ao Xu ◽  
Junpeng Li ◽  
...  
Keyword(s):  
Satellite System ◽  
Ionospheric Delay ◽  
Navigation Satellite ◽  
Dual Frequency ◽  
Correction Model ◽  
Beidou Navigation Satellite System ◽  
Correction Rate ◽  
Klobuchar Model ◽  
Delay Correction ◽  
Ionospheric Grid

Ionospheric delay is one of the main errors in the satellite navigation and positioning system. At present, ionospheric delay correction model and grid ionospheric information are provided to correct the error in BeiDou Navigation Satellite System (BDS). The ionospheric delay correction model is the Klobuchar model with 8 parameters at the geographic latitude for basic navigation. Grid ionospheric information is the ionospheric grid map covering China region for enhanced services. The dual-frequency pseudo-range combination data and ionospheric data from 2013 to 2018 have been used to make comprehensive assessments of the correction performance of BDS Klobuchar model and ionospheric grid information. The average correction rate of ionospheric grid information is about 85%, and the average correction rate of BDS Klobuchar model is about 73%. The correction accuracy of BDS Klobuchar model varies little, and the ionospheric grid information has a single-peak structure. The correction accuracy in summer and autumn is slightly higher than that in winter and spring. Changes in solar activity have a greater impact on BDS Klobuchar model correction bias. Ionospheric grid information owns relatively strong anti-disturbance ability, and BDS Klobuchar model also has a definite anti-disturbance capability compared with the GPS Klobuchar model.

scholarly journals Evaluation of Seasonal Variability of First-order Ionospheric Delay Correction at L5 and S1 Frequencies Using Dual-frequency Navic System

2021 ◽  
Author(s):  
Sharat chandra Bhardwaj ◽  
Anurag Vidyarthi ◽  
Bhajan Singh Jassal ◽  
Ashish kumar Shukla
Keyword(s):  
Seasonal Variability ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Dual Frequency ◽  
Satellite Constellations ◽  
Total Electron ◽  
First Order ◽  
Seasonal Characteristics ◽  
Geosynchronous Satellites ◽  
Delay Correction

Abstract For the precise positioning application it is important to determine and eliminate the positioning error introduced by various sources such as the ionosphere. To develop a standalone precise navigation system, India has launched the seven satellite constellations of NavIC (Navigation with Indian Constellation) system to provide precision positioning over India and surrounded landmass. Since the ionospheric delay depends on the frequency of the satellite signal and NavIC systems work at different frequencies (L5 and S1) than GPS systems (L1 and L2), it is not possible to use the GPS data-driven study for NavIC based location calculations directly. Thus there is a need for a specialized ionospheric study for NavIC systems. In addition, the ionospheric delay is directly proportional to Slant Total Electron Content (STEC) which is dependent upon diurnal and seasonal solar activity. To achieve accurate positioning facilities, there is also a need for evaluation for seasonal variability of ionospheric delay correction for NavIC receivers. This paper deals with the STEC estimation; its smoothing, and removal of instrumental biases from STEC. The determined true STEC has been used to determine first-order ionospheric delay at L5 and S1 frequencies. The delay at S1 has been found less (2 to 7m) as compared to L5 (10 to 30m). Furthermore, the seasonal variability of ionospheric delay has been analyzed using about 19 months of data (from June 2017 to December 2018) and found that the ionospheric delay follows unique seasonal characteristics which can be utilized for delay modeling. It has been also observed that the geostationary satellites of the NavIC system are more appropriate than geosynchronous satellites for ionospheric related studies.

scholarly journals Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

2020 ◽  
Vol 12 (7) ◽  
pp. 1215 ◽  
Author(s):  
Chao Yang ◽  
Jing Guo ◽  
Tao Geng ◽  
Qile Zhao ◽  
Kecai Jiang ◽  
...  
Keyword(s):  
Ionospheric Delay ◽  
Global Navigation Satellite Systems ◽  
Single Frequency ◽  
Electron Content ◽  
Ionospheric Correction ◽  
Total Electron ◽  
Correction Model ◽  
Satellite Systems ◽  
Satellite Navigation System ◽  
Navigation Data

For single-frequency Global Navigation Satellite Systems (GNSSs) users, ionospheric delay is the main error source affecting the accuracy of positioning. Applying a broadcast ionospheric correction model to mitigate the ionospheric delay is essential for meter-to-decimeter-level accuracy positioning. To provide support for real-time single-frequency operations, particularly in the China area, we assessed the performance of three broadcast ionospheric correction models, namely, the Neustrelitz total electron content (TEC) broadcast model (NTCM-BC), the BeiDou global broadcast ionospheric delay correction model (BDGIM), and the Klobuchar model. In this study, the broadcast coefficients of Klobuchar and BDGIM are obtained from the navigation data files directly. Two sets of coefficients of NTCM-BC for China and global areas are estimated. The slant total electron contents (STEC) data from more than 80 validation stations and the final vertical TEC (VTEC) data of the Center for Orbit Determination in Europe (CODE) are used as independent benchmarks for comparison. Compared to GPS STEC during the period of Day of Year (DOY) 101~199, 2019, the ionospheric correction ratio of NTCM-BC, BDGIM, and Klobuchar are 79.4%, 64.9%, and 57.7% in China, respectively. For the global area, the root-mean-square (RMS) errors of these three models are 3.67 TECU (1 TECU = 1016 electrons/m2), 5.48 TECU, and 8.92 TECU, respectively. Compared to CODE VTEC in the same period, NTCM-BC, BDGIM, and Klobuchar can correct 72.6%, 69.8%, and 61.7% of ionospheric delay, respectively. Hence, NTCM-BC is recommended for use as the broadcast ionospheric model for the new-generation BeiDou satellite navigation system (BDS) and its satellite-based augmentation system.

Performance Evaluation of USTEC Product for Single-Frequency Precise Point Positioning

GEOMATICA ◽  
2013 ◽  
Vol 67 (4) ◽  
pp. 253-257 ◽  
Author(s):  
Mahmoud Abd El-Rahman ◽  
Ahmed El-Rabbany
Keyword(s):  
Total Electron Content ◽  
Precise Point Positioning ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Gps Receivers ◽  
Mitigation Techniques ◽  
Point Positioning

Geodetic-grade dual-frequency GPS receivers are typically used for precise point positioning (PPP). Unfortunately, these receiver systems are expensive and may not provide a cost-effective solution in many instances. The use of low-cost single-frequency GPS receivers, on the other hand, are limited by the effect of ionospheric delay. A number of mitigation techniques have been proposed to account for the effect of ionospheric delay for single-frequency GPS users. Unfortunately, however, those mitigation techniques are not suitable for PPP. More recently, the U.S. Total Electron Content (USTEC) product has been developed by the National Oceanic and Atmospheric Administration (NOAA), which describes the ionospheric total electron content in high resolution over most of North America. This paper investigates the performance of USTEC and studies its effect on single-frequency PPP solution. A performance comparison with two widely-used ionospheric mitigation models is also presented.

scholarly journals Single Point Positioning with Vertical Total Electron Content estimation based on single epoch data

2020 ◽  
Author(s):  
Artur Fischer ◽  
Sławomir Cellmer ◽  
Krzysztof Nowel
Keyword(s):  
Single Point ◽  
Error Reduction ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Single Point Positioning ◽  
External Data ◽  
Point Positioning

Abstract. This paper proposes a new mathematical method of ionospheric delay estimation in single point positioning (SPP) using a single-frequency receiver. The proposed approach focuses on the ΔVTEC component estimation (MSPPwithdVTEC) with the assumption of an initial and constant value equal to 5 in any observed epoch. The principal purpose of the study is to examine the reliability of this approach to become independent from the external data in the ionospheric correction calculation process. To verify the MSPPwithdVTEC, the SPP with the Klobuchar algorithm was employed as a reference model, utilizing the coefficients from the navigation message. Moreover, to specify the level of precision of the MSPPwithdVTEC, the SPP with the IGS TEC map was adopted for comparison as the high-quality product in the ionospheric delay determination. To perform the computational tests, real code data was involved from three different localizations in Scandinavia using two parallel days. The criterion were the ionospheric changes depending on geodetic latitude. Referring to the Klobuchar model, the MSPPwithdVTEC obtained a significant improvement of 15–25 % in the final SPP solutions. For the SPP approach employing the IGS TEC map and for the MSPPwithdVTEC, the difference in error reduction was not significant, and it did not exceed 1.0 % for the IGS TEC map. Therefore, the MSPPwithdVTEC can be assessed as an accurate SPP method based on error reduction value, close to the SPP approach with the IGS TEC map. The main advantage of the proposed approach is that it does not need external data.

scholarly journals Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Xiao Yu ◽  
Chengli She ◽  
Weimin Zhen ◽  
Nava Bruno ◽  
Dun Liu ◽  
...  
Keyword(s):  
Solar Activity ◽  
Primary Source ◽  
Optimization Procedure ◽  
Single Frequency ◽  
Electron Content ◽  
Coefficient Function ◽  
Ionospheric Correction ◽  
Total Electron ◽  
Function Expression ◽  
Global Ionospheric Maps

The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions.

scholarly journals On GPS L1 Positioning Errors’ Estimation in the Adriatic Region

2020 ◽  
Vol 58 (1) ◽  
pp. 169-184
Author(s):  
Aleksandar Žic ◽  
Barbara Pongračić ◽  
Serđo Kos ◽  
David Brčić
Keyword(s):  
Space Weather ◽  
Environmental Conditions ◽  
Single Frequency ◽  
Positioning Error ◽  
International Gnss Service ◽  
Ground Truth Data ◽  
Positioning Errors ◽  
Satellite Positioning ◽  
Errors Estimation ◽  
Adriatic Region

Prediction of satellite positioning errors represents a substantial step towards the Global Navigation Satellite System (GNSS) performance assessment. Satellite positioning accuracy in the particular area can be expected to be similar due to prevailing environmental conditions. This similarity opens the opportunity to estimate and predict the positioning errors of close locations. The paper aims to develop a regional model of positioning errors estimation for Global Positioning System (GPS) single-frequency receivers based on ground truth data from reference stations, in this phase considering different levels of space weather activity as one f the criteria defining environmental conditions. The model should provide a simple positioning error prediction in cases where reference stations and respective data do not exist. The space weather conditions were examined to determine the influence on GPS satellite positioning performance at three selected International GNSS Service (IGS) stations in the Adriatic Region - Graz, Padua, and Matera. The mutual relations in terms of positioning error patterns were elaborated. The same 15-day period in three consecutive years was analysed. Pearson’s coefficient was utilised as a major indicator for determining the degree of correlation. The data from IGS stations Padua and Graz showed better, significant correlation results. The IGS station Matera, located farther and southward slightly differed in positioning deviations’ patterns and was not used for the model development. Satellite positioning errors of IGS Padua were used as a reference to determine the positioning errors of IGS Graz. Due to the significant correlation results, the linear regression model has been developed for the latitude, longitude, and height positioning errors. The final model coefficients were calculated as average values of the model coefficients for latitude, longitude, and height errors for elaborated periods. The cross-validation with five folds has been carried out, showing good model performance with R2 values of 0.7785 for geographic latitude, 0.8132 for the geographic longitude, and 0.7796 for height above sea level, respectively. The validation showed that the model could be applied during all levels of space weather activity on a regional basis.

scholarly journals Solving a navigation problem with the total electron content model GEMTEC

2019 ◽  
Vol 5 (1) ◽  
pp. 82-85
Author(s):  
Андрей Холмогоров ◽  
Andrey Kholmogorov ◽  
Всеволод Иванов ◽  
Vsevolod Ivanov ◽  
Олег Горбачев ◽  
...  
Keyword(s):  
Single Frequency ◽  
Electron Content ◽  
International Network ◽  
Total Electron ◽  
Positioning Errors ◽  
Interface Control ◽  
Klobuchar Model ◽  
Using Data ◽  
Total Electronic Content ◽  
Gps System

This article explores the possibility of improving the accuracy of positioning in single-frequency satellite radio navigation equipment through the use of an empirical model of the total electronic content GEMTEC. The effectiveness of this model is compared with that of the Klobuchar model, which is recommended for the GPS interface control document. We conducted testing at our observation points, using data from the international network of IGS stations in the GPS system. The use of the international network allowed us to select a long period of time for the testing from 2001 to 2017. As a result, it was shown that the GEMTEC model significantly reduces the average positioning errors as compared to the Klobuchar model. We also demonstrate the possibility of introducing the GEMTEC model and its full-featured use in single-frequency home-class receivers, for example, in the Russian receiver MNP-M7.

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