Browsing by Subject "Ionospheric total electron content"
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Item Open Access Ionospheric total electron content estimation using IONOLAB method(IEEE, 2007) Nayir, H.; Arıkan, F.; Erol, C. B.; Arıkan, OrhanIonosphere which is an important atmospheric layer for HF and satellite communications, can be investigated through Total Electron Content (TEC). Global Positioning System provides cost-effective means for TEC estimation. Regularized TEC estimation method (D-TEI) is developed to estimate high resolution, robust TEC values. The method combines measurements of GPS satellites above 10° elevation limit and estimates can be obtained with 30 s time resolution. In this paper, parameters that are used in D-TEI method such as ionospheric height, weighting function, and satellite receiver biases are studied. It is found that TEC estimation results of D-TEI method is almost independent of ionospheric height. Different weighting functions are tried and the weighting function that minimizes non-ionospheric effects is selected. By using satellite and receiver biases in the correct form consistent TEC estimation results are obtained with IGS analysis centers. In this paper, the method is improved to include phase measurements. Taking either pseudorange or phase measurements as input, high resolution, robust TEC estimates are obtained using D-TEI method.Item Open Access Parameter estimation for synthetic TEC surfaces by using Particle Swarm Optimization(IEEE, 2012) Gökdaǧ, Y.E.; Arikan F.; Toker, C.; Arıkan, OrhanIn this study, parameter estimation is made for global ionospheric Total Electron Content (TEC) on both noiseless and noisy synthetic surfaces by using modified Particle Swarm Optimization (PSO). In addition, the improvements made in the PSO algorithm to obtain better results are presented. Trend functions that best regionally and globally represent the quiet and distorted ionosphere are given. For noisy trend surfaces, additive white Gaussian noise is added on trend surfaces according to latitude. International GPS System stations (IGS) are used for regional sampling whereas TNPGN-Active stations are used for both regional and global sampling. A brief discussion of PSO and its improvements for modified PSO is provided. Performance and error criterias are determined for the results of noisy and noiseless dual-core Gaussian trend surfaces. © 2012 IEEE.