GPS and navigation GPS)، GLONASS، GALILEO
Tania Mansour Fallah; Behzad Voosoghi; Seyyed Reza Ghaffari-Razin
Volume 17, Issue 1 , March 2024, , Pages 21-36
Abstract
In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. ...
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In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. Comparing the results of the new model with support vector regression (SVR), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), Kriging model, GIM and international reference ionosphere 2016 (IRI2016) as well as TEC obtained from GPS. The analyzes performed show that the averaged RMSE of ANN, ANFIS, SVR, LS-SVR, Kriging, GIM and IRI2016 models in two interior control stations are 3.91, 2.73, 1.27, 1.04, 2.70, 3.02 and 6.93 TECU, respectively. Also, the averaged relative error of the models in two interior control stations was calculated as 15.98%, 9.39%, 7.85%, 6.09%, 11.60%, 12.54% and 26.56%, respectively. Analysis of the PPP method shows an improvement of 50 mm in the coordinate components using the LS-SVR model. The results of this paper show that the LS-SVR model can be considered as an alternative to global and empirical models of the ionosphere in the study area.
Remote sensing
Fereydon Nobakht Orsi; Abdolreza Safari; Amir Khodabandeh
Volume 14, Issue 3 , September 2021, , Pages 101-108
Abstract
In this paper, we discussed standard point positioning technique based on the single frequency code-based (C/A) receivers. Then, we presented its performance by means of different measures. However, the use of one single frequency GPS receiver to obtain high-precision positioning make a major challenge ...
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In this paper, we discussed standard point positioning technique based on the single frequency code-based (C/A) receivers. Then, we presented its performance by means of different measures. However, the use of one single frequency GPS receiver to obtain high-precision positioning make a major challenge due to the environmental biases, in particular the ionospheric effects are handled. The main objective of the present study is to integrate a inospheric model such as Klobuchar Inospheric Model (KIM) with imprecise code (C/A) observations under intense geomagnetic storm conditions, then, to obtain dm level positioning accuracy using Kalman filter. For this purpose we used code (C/A) observations on two different days (February 26, 2018 and December 20, 2015) at Tehran station. The results show that we could obtain multi-dm level positioning accuracy under geomagnetic storm condition by using Kalman filter that will be important in the field of kinematic applications.
GPS and navigation GPS)، GLONASS، GALILEO
Mir Reza Ghaffari Razin; Behzad Voosoghi
Volume 13, Issue 3 , September 2020, , Pages 39-50
Abstract
In this paper, WNN with PSO training algorithm is used to modeling and prediction of time-dependent ionosphere total electron content (TEC) variations. 2 different combinations of input observations are evaluated. The number of stations used to train of WNN with PSO algorithm selected 20 and 10. In all ...
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In this paper, WNN with PSO training algorithm is used to modeling and prediction of time-dependent ionosphere total electron content (TEC) variations. 2 different combinations of input observations are evaluated. The number of stations used to train of WNN with PSO algorithm selected 20 and 10. In all testing mode, 3 GPS stations with proper distribution are considered as a testing stations. Statistical indicators relative error, dVTEC and correlation coefficient were used to assess the wavelet neural network model. The results of proposed model compared with GPS-TEC and international reference ionosphere 2012 (IRI-2012) TEC. Average relative error computed in 3 test stations are 5.43% with 20 training station and 9.05% with 10 training station. Also the correlation coefficient calculated in 3 test stations are 0.954 with 20 training station and 0.907 with 10 training station. The results of this study show that the WNN with PSO algorithm is a reliable model to predict the temporal variations in the ionosphere.
Space Ground Segment: receiving, transmitting, controlling and data processing
Ali Sadeghzade; S. Hasan Sedighi; Mohamad Soleimani
Volume 13, Issue 3 , September 2020, , Pages 63-68
Abstract
In this paper, an anti-jamming GPS array antenna with seven antenna elements on the conformal structure is proposed for GPS applications by switching on/off the antenna ports. In this proposed antenna, when the received power is high, the antenna feeds are switched off to create null in the direction ...
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In this paper, an anti-jamming GPS array antenna with seven antenna elements on the conformal structure is proposed for GPS applications by switching on/off the antenna ports. In this proposed antenna, when the received power is high, the antenna feeds are switched off to create null in the direction of jammer to reduce the jammer effect. This structure composed of seven patch elements where each element placed on special face of the structure. Whatever antennas be more directive, we can create deeper nulls. These specifications introduce this antenna as a good candidate for GPS applications to mitigate the jammer effects.
Sh. Amiri; M. Fahami
Volume 6, Issue 2 , July 2013, , Pages 21-28
Abstract
In this paper GPS radio occultation has been introduced as a way to extract the electron density of the ionosphere. A GPS radio occultation occurs when a receiver on-board a LEO spacecraft tracks a GPS satellite as it sets or rises through the earth’s atmosphere. The recorded occulted signal phase ...
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In this paper GPS radio occultation has been introduced as a way to extract the electron density of the ionosphere. A GPS radio occultation occurs when a receiver on-board a LEO spacecraft tracks a GPS satellite as it sets or rises through the earth’s atmosphere. The recorded occulted signal phase and amplitude of the tracked satellite can then be analyzed to derive atmospheric electron density.TEC Monitoring has been studied tocorrect the error caused by the ionospher electron density in the telecommunication satellite global positioning system are briefly introduced as a tool for this method. One occultation event studied near one of the brazilion oson destations and the electron density curves obtained from the data reported Brazil Ionosonde are compared with radio methods.
Jamal Asgari; Ali Reza Amiri -Simkooei; Farzane Zanganeh-nejad
Volume 5, Issue 3 , October 2012, , Pages 49-57
Abstract
Inertial Navigation System (INS) and Global Positioning System (GPS), are used in various navigation and positioning applications. Because each of the INS and GPS technologies has some limitations and advantages, during last two decades, the systems integration has been widely used for accurate and reliable ...
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Inertial Navigation System (INS) and Global Positioning System (GPS), are used in various navigation and positioning applications. Because each of the INS and GPS technologies has some limitations and advantages, during last two decades, the systems integration has been widely used for accurate and reliable navigation and positioning. In an integrated system, accurate GPS observations are used to estimate the high rate INS errors and state vector (including INS error vector, position, velocity and other optional parameters). A field test results are presented in this paper. The goal of this test is to compare the coordinates of a relatively low cost INS, GPS RTK coordinates, and the integrated GPS/INS results. The decentralized approach has been used for this integration.
F. Nobakht-Orsi; M. A. Sharifi; A. R. Safari
Volume 4, Issue 1 , July 2011, , Pages 15-22
Abstract
In this paper, Hilbert Huang transform (HHT) for time series analysis of the status of permanent GPS stations can be provided. Hilbert Huang transform and its, related spectrun is a new method for the analysis of nonlinear processes.This method represents not only a precision analysis in the time-frequency ...
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In this paper, Hilbert Huang transform (HHT) for time series analysis of the status of permanent GPS stations can be provided. Hilbert Huang transform and its, related spectrun is a new method for the analysis of nonlinear processes.This method represents not only a precision analysis in the time-frequency space, but also it declares the physics of the dynamic processes. This method has two speps. At the first step, the data is disintegrated into IMF elements by EMD method. At the second step Hilbert transform is applied for IMF elements and distribution of the time-frequency –Hilbert energy spectrum is then determined. In this spectrum, Location, frequency and energy defined by time events for the Hillbert transform will be reserved. So instantaneous frequency will have a major role in this method.
