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Ionospheric delay, can be derived from dual frequency GNSS signals, and then converted into the Vertical Total Electron Contents (VTEC) along the signal path. Various models were devised to calculate VTEC. Examples of such models are the polynomial function model and spherical harmonics model. A common hypothesis of these models is that they are co...
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In this study, we analyze the climatology of ionosphere over Nepal based on GPS derived VTEC observed from four stations: KKN4 (27.80° N, 85.27° E), GRHI (27.95° N, 82.49° E), JMSM (28.80° N, 83.74° E), DLPA (28.98° N,82.81° E) during years 2008 to 2018. The study illustrates the diurnal, monthly, annual, seasonal and solar cycle variations of VTEC...
The computation of vertical total electron content (VTEC) maps has become an important issue gradually for the international GNSS service. Given the current literature reports, little research is involved in the quantitative analysis of each error of the VTEC map and the spatiotemporal characteristic of global VTEC accuracy. Based on the single lay...
Global navigation satellite system (GNSS) signals are significantly affected by the ionosphere. An efficient way to assess the ionospheric effects on GNSS signals is by retrieving the vertical total electron content (VTEC). Here, we propose convolutional recurrent neural network architectures to forecast VTEC based on global ionosphere maps (GIMs)...
The determination of the ionospheric perturbation degree is essential to describe the ionosphere state for space weather monitoring. A new method for estimating the spatial and temporal components of the Vertical Total Electron Content (VTEC) gradient is introduced. The new method is based on VTEC estimated at each grid point of Global Ionosphere M...
Extra constraints are always brought into an ionosphere tomographic model to strengthen its robustness. However, existent models using the constraints either show a weak restriction, amplifying the model’s uncertainties, or demonstrate a strong restriction, decreasing the model’s flexibility. Empirical Orthogonal Function (EOF), as a kind of basis...
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... The results confirm that due to the lack of International GNSS Service (IGS stations) over the North Africa, GIMs have no effect for mitigating ionospheric error. A new value for the ionosphere correction VTEC values obtained by a regional developed algorithm based on zero-differenced phase ionospheric delay (ZDPID) [6]. These new values of VTEC can be feeded into GIMs-IONEX file for the specified stations data. ...
... IGS directly manages ~400 permanent GNSS stations observing 4-12 satellites at 30 s rate: more than 250,000 STEC observations/hour worldwide, but there is lack of stations at some areas (e.g., over the oceans).Because of the results of[6] is considered as a milestone of the current study, the proposed method was tested on abaseline of Borg ~ Said 264.982 km. The kinematic processing of the specified baseline was done twice by Trimble Total Control 2.7 "TTC", one by standard default processing parameters (D.D) and the second time with using modified IONEX-GIM values (D.D.M-GIM). ...
Abstract —The most ideal GNSS exactness, a couple of centimeters or better, is gotten by utilizing transporter stage estimations from double recurrence collectors. Be that as it may, single-recurrence beneficiaries can give decimeter precision at a diminished cost for the recipient and for the most part achieve this level of exactness substantially quicker than a double recurrence beneficiary does. The most ideal GNSS accu-shocking, a couple of centimeters or better, is gotten by utilizing bearer stage estimations from double recurrence collectors. How-ever, single-recurrence beneficiaries can give decimeter accu-shocking at a decreased cost for the beneficiary and by and large achieve this level of exactness significantly speedier than a double recurrence re-ceiver does. An essential thought with PPP is the ne-cessity to amend for different impacts that would somehow or another counterbalance in relative situating methods utilizing at least one collectors.
... The results confirm that due to the lack of International GNSS Service (IGS stations) over the North Africa, GIMs have no effect for mitigating ionospheric error. A new value for the ionosphere correction VTEC values obtained by a regional developed algorithm based on zero-differenced phase ionospheric delay (ZDPID) [6]. These new values of VTEC can be feeded into GIMs-IONEX file for the specified stations data. ...
... IGS directly manages ~400 permanent GNSS stations observing 4-12 satellites at 30 s rate: more than 250,000 STEC observations/hour worldwide, but there is lack of stations at some areas (e.g., over the oceans).Because of the results of[6] is considered as a milestone of the current study, the proposed method was tested on abaseline of Borg ~ Said 264.982 km. The kinematic processing of the specified baseline was done twice by Trimble Total Control 2.7 "TTC", one by standard default processing parameters (D.D) and the second time with using modified IONEX-GIM values (D.D.M-GIM). ...
Kinematic precise positioning is one of the main constraints of Global Positioning System. Double differe Point Positioning method (PPP) is the most accurate positioning in GPS committee. The ionospheric delay in the pro positioning system (GPS) signals is one of the main sources of errors in GPS precise positioning and navigation. This in PPP approach by ionosphere free combination and reduced relatively in the approach of double differencing in ca km), what about base line over 50 km. In this paper, Ionospheric delay has been eliminated with the availability o ionospheric map produced by varies organizations (e.g., International GNSS service (IGS)). [1], evaluate the ionosph Global Ionospheric Maps, provided in (IONEX) files produced by IGS. He shows that there is no significant effect of values on the solution of kinematic processing. The primary goal of this paper is to test the effect of evaluated Global (GIMs), Modified-GIM, on precise relative kinematic positioning over varies baselines lengths extended up to hundre comparing the relative kinematic solution with modified GIM for several baselines and kinematic PPP solution for More accurate results were obtained by correcting ionospheric error over kinematic solution of many baseline lengths kinematic PPP solution for the rover stations was evaluated. It can be concluded that, PPP still the more accurate than even after correcting ionospheric error over longer baseline.
Due to the lack of coverage of IGS in Africa, especially over North Africa, and the construction revolution of infrastructure in Egypt, a geodetic CORS stations network was established in 2012. These CORS stations are operated by the Egyptian Surveying Authority (Egy. SA) and cover the whole of Egypt. The paper presents a fully developed regional ionosphere model (RIM) depending on the Egyptian CORS stations. The new model and the PPP solution were obtained using Bernese GNSS V. 5.2 software. An observation data series of eight days (DOY 201–208)/2019 was used in this study. Eighteen stations were used to develop the RIM model for each day; fifteen stations were used to validate the new RIM model. A static SF-PPP solution was obtained using the CODE-GIM and RIM models. Comparing the outcomes to the reference network solution, based on the recently developed RIM model, the solution showed a mean error of 0.06 m in the East direction, 0.13 m in the North direction, and 0.21 m in the height direction. In the East, North, and height directions, this solution improves the SF-PPP result achieved by the Global Ionosphere Maps (CODE-GIM) model by 60%, 68%, and 77%, respectively.
