Comparison Of GPS/Galileo Single Frequency Ionospheric Models With Vertical Tec Maps

Farah, Ashraf

doi:10.2478/v10018-009-0008-5

Cited by 11 publications

(5 citation statements)

References 4 publications

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“…Alongside its applications the performances of the model have been tested in different regions from time to time. It has been shown that both versions of the model, compared to other model, are well suited for GALILEO single frequency ionospheric error correction [ Bidaine and Warnant , 2011; Radicella et al , 2008; Farah , 2008]. Jodogne et al [2004] compared the modeled vTEC (using NeQuick 1) with measurements at midlatitude regions and found good agreement.…”

Section: Introductionmentioning

confidence: 99%

TEC ingestion into NeQuick 2 to model the East African equatorial ionosphere

et al. 2012

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[1] NeQuick 2 ionospheric empirical model depends on global ionospheric coefficients that are estimated from unevenly distributed ionosonde measurements. In regions, like Africa, where very few observational data were available until recently, the model estimated the ionospheric peak parameters by interpolation. When one wants to employ the model to specify the ionosphere where very few data have been used for model development, the performances of the model need careful validation. This study investigates the performances of NeQuick 2 in the East African region by assisting the model with measurements from a single Global Positioning System (GPS) receiver, which has been deployed recently. This can be done by first calculating an effective ionization level that drives NeQuick 2 to compute slant total electron content (sTEC) which fits, in the least square sense, with the measurements taken from a single GPS receiver. We then quantify the performances of NeQuick 2 in reproducing the measured TEC by running the model at four other locations, where GPS stations are available, using the same effective ionization level that we calculated from a single GPS station as a driver of the model. Finally, the performances of the model before and after data ingestion have been investigated by comparing the model results with the experimental sTEC and vertical TEC (vTEC) obtained from the four test stations. Three months data during low solar activity conditions have been used for this study. We have shown that the capability of NeQuick 2, in describing the East African region of the ionosphere, can be improved substantially by data ingestion. We found that the model after ingestion reproduces the experimental TEC better as far as about 620 km away from the reference station than that before adaptation. The statistical comparisons of the performances of the model in reproducing sTEC before and after ingestion are also discussed in this study.Citation: Nigussie, M., S. M. Radicella, B. Damtie, B. Nava, E. Yizengaw, and L. Ciraolo (2012), TEC ingestion into NeQuick 2 to model the East African equatorial ionosphere, Radio Sci., 47, RS5002,

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Section: Introductionmentioning

confidence: 99%

TEC ingestion into NeQuick 2 to model the East African equatorial ionosphere

et al. 2012

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“…The eight time-varying coefficients of the model are broadcast in the GPS navigation message. GPS master control station select those coefficients from 370 possible sets of constants based on two parameters, day of the year and average solar 10.7-cm flux value (Farah, 2008).…”

Section: Gps-klobuchar Modelmentioning

confidence: 99%

“…(Dodson, 1988) concluded that the correction accuracy of the model is about 50-60% of the total delay. The model is unable to show any significant fluctuations from day to day as it assumes an ideal smooth behaviour of the ionosphere (Farah, 2008). (Newby et al, 1990) concluded also that the range error by the model can be of order of 50 m under severe ionosphere activity at low elevations.…”

Section: Gps-klobuchar Modelmentioning

confidence: 99%

Single-Frequency Ionospheric-Delay Correction from BeiDou & GPS Systems for Northern Hemisphere

Farah

2019

Artificial Satellites

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The range delay caused by the ionosphere layer is the major current source of error for GNSS users with single-frequency receivers. GNSS advice users to correct this type of error using ionospheric models whose coefficients are sent in their navigation messages. GPS-users use the Klobuchar model to correct this type of error. GPS navigation message contains the model’s eight coefficients which vary on the basis of seasonal ionospheric variations and average solar flux. The correction accuracy of Klobuchar model is about 50% (rms) of the ionospheric range delay. Beidou system calculates and broadcast 8 parameters of Klobuchar model based on continuous monitoring stations. BeiDou system updates the ionospheric coefficients every two hours. GPS-Klobuchar model uses completely different coefficients than BeiDou-Klobuchar model. This research demonstrates a comparison study between the Klobuchar model using the GPS broadcast coefficients and the same model using BeiDou-coefficients. The correction accuracy offered by the two models has been judged using the most accurate International GNSS Service-Global Ionospheric Maps (IGS-GIMs) for three different-latitude stations along northern hemisphere, one station in low-latitude region, the second station is in mid-latitude region and the third station is in high-latiude region to reflect models’ behaviour in different geographic regions. The study was applied over three different months of the year 2017 that each of them reflects a different activity state for the ionosphere layer. The study proves that BeiDou model is able to show the ionosphere’s day-to-day fluctuations while GPS model can’t. It can be concluded that GPS model offers better behaviour than BeiDou model in correcting range delay in low-latitude and high-latitude geographic regions under any activity state for the ionosphere. BeiDou model offers better correction accuracy than GPS model in mid-latitude under any activity state for the ionosphere.

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“…Computation of vertical delays at an IGP using the WLS method For each IGP, the vertical ionospheric delay can be estimated using the WLS grid estimator weighted with a nominal ionospheric delay model, such as the GPS Klobuchar model or Galileo NeQuick model. 16,17) This approach estimates the vertical delay and its error bound at each grid point, allowing better monitoring of local disturbances and more robust integrity monitoring. Moreover, the WLS estimator is easy to implement and less computationally expensive than other estimators because there is no complex matrix inversion.…”

Section: Estimation Of Vertical Delays At Ippsmentioning

confidence: 99%

Adaptive Ionospheric Pierce Point Cut-off Radius Control for Korean Satellite Navigation Systems

Joo

Heo

Bang

2015

Trans. Japan Soc. Aero. S Sci.

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The largest source of positioning error for single-frequency users of the Global Navigation Satellite System (GNSS) is typically the radio delay caused by the ionosphere. Although several analytic function-based models for correcting ionospheric errors are available, grid-based models are preferred because of their high estimation accuracy and low complexity. We propose an adaptive ionospheric pierce point cut-off radius control algorithm for the high-resolution, grid-based correction of ionospheric errors. The proposed scheme adjusts the IPP cut-off radii by comparing the target IPP densities with the current effective densities. Simulation results show that our method gives the required effective IPP density using this cut-off radius control, thus improving the accuracy and availability of the correction service. It is expected that the proposed scheme will make high-resolution, grid-based ionospheric correction available for Korean satellite navigation systems with a local distribution of ground reference stations. System development costs will also be reduced since it will require fewer reference stations.

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Comparison Of GPS/Galileo Single Frequency Ionospheric Models With Vertical Tec Maps

Cited by 11 publications

References 4 publications

TEC ingestion into NeQuick 2 to model the East African equatorial ionosphere

TEC ingestion into NeQuick 2 to model the East African equatorial ionosphere

Single-Frequency Ionospheric-Delay Correction from BeiDou & GPS Systems for Northern Hemisphere

Adaptive Ionospheric Pierce Point Cut-off Radius Control for Korean Satellite Navigation Systems

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