Abstract
Abstract. Precise total electron content (TEC) is required to produce accurate spatial and temporal resolution of global ionosphere maps (GIMs). Receivers and satellite differential code biases (DCBs) are one of the main error sources in estimating precise TEC from Global Positioning System (GPS) data. Recently, researchers have been interested in developing models and algorithms to compute DCBs of receivers and satellites close to those computed from the Ionosphere Associated Analysis Centers (IAACs). Here we introduce a MATLAB code called Multi Station DCB Estimation (MSDCBE) to calculate satellite and receiver DCBs from GPS data. MSDCBE based on a spherical harmonic function and a geometry-free combination of GPS carrier-phase, pseudo-range code observations, and weighted least squares was applied to solve observation equations and to improve estimation of DCB values. There are many factors affecting the estimated values of DCBs. The first one is the observation weighting function which depends on the satellite elevation angle. The second factor is concerned with estimating DCBs using a single GPS station using the Zero Difference DCB Estimation (ZDDCBE) code or using the GPS network used by the MSDCBE code. The third factor is the number of GPS receivers in the network. Results from MSDCBE were evaluated and compared with data from IAACs and other codes like M_DCB and ZDDCBE. The results of weighted (MSDCBE) least squares show an improvement for estimated DCBs, where mean differences from the Center for Orbit Determination in Europe (CODE) (University of Bern, Switzerland) are less than 0.746 ns. DCBs estimated from the GPS network show better agreement with IAAC than DCBs estimated from precise point positioning (PPP), where the mean differences are less than 0.1477 and 1.1866 ns, respectively. The mean differences of computed DCBs improved by increasing the number of GPS stations in the network.
Highlights
Total electron content (TEC) is an important parameter in the study of ionospheric dynamics, structures, and variabilities
Reliable global ionosphere maps (GIMs) and accurate differential code biases (DCBs) of satellites and the International GNSS Service (IGS) stations can be obtained from Ionosphere Associated Analysis Centers (IAACs) like Center for Orbit Determination in Europe (CODE) (Schaer, 1999), the European Space Agency (ESA, Germany) (Feltens and Schaer, 1998), the Jet Propulsion Laboratory (JPL, USA) (Mannucci et al, 1998), and UPC (Technical University of Catalonia, Spain) (Hernández-Pajares et al, 1999; Orús et al, 2005)
In this study we introduce a mathematical model estimating satellites and receiver DCBs for a Global Positioning System (GPS) network based on a spherical harmonic function (SHF) written under the MATLAB environment; the developed mathematical model uses a geometry-free combination of pseudo-range observables (P code)
Summary
Total electron content (TEC) is an important parameter in the study of ionospheric dynamics, structures, and variabilities. Careful estimation of the DCBs is required to obtain accurate TEC, which is used in several applications, such as in several ionospheric prediction models, and in the correction of GPS positioning measurements (McCaffrey et al, 2017). Estimating DCBs for receivers and satellites from GPS observations depends on two approaches, the relative and absolute methods. Et al.: Estimating satellite and receiver differential code bias network, while the absolute method determines DCBs from a single station (Sedeek et al, 2017). Reliable GIMs and accurate DCBs of satellites and the International GNSS Service (IGS) stations can be obtained from IAACs like CODE (Schaer, 1999), the European Space Agency (ESA, Germany) (Feltens and Schaer, 1998), the Jet Propulsion Laboratory (JPL, USA) (Mannucci et al, 1998), and UPC (Technical University of Catalonia, Spain) (Hernández-Pajares et al, 1999; Orús et al, 2005).
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