Estimating the total electron content absolute value from the GPS/GLONASS data

Abstract

a b s t r a c tWhen determining the absolute oblique total electron content (TEC) of the ionosphere using both GLON-ASS/GPS code and phase measurements, there occurs a systematic error associated with the differential code biases (DCBs). A 1-ns DCB leads to the $2.9 TECU error when determining L1-L2 dual-frequency oblique TEC. We have developed an algorithm for DCB estimation from the data of a single GPS/GLONASS station. Presented are the results of the algorithm operation compared with the oblique TEC correction by using CODE laboratory DCB data. Ó 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Global navigation satellite systems (GNSS) have enabled to study the ionosphere in different regions of the world [1]. One may say today that such studies have become global and have involved both more-or-less investigated mid-and equatorial latitudes and poorly investigated Arctic and Antarctic ones. The total electron content (TEC) of the Earth ionosphere can be determined from code and phase dual-frequency pseudorange measurements performed by receivers of GNSS signals. This technique is widely described in the literature [4].Phase measurements are weakly noised, but they are relative due to the ambiguity of the initial phase definition. Code measurements are absolute, however, they feature very high noise, up to hundred percent at low elevation angles. For this reason, to obtain the absolute TEC values, phase measurements are usually used, and the ambiguity is eliminated with code ones. Thus, there occurs a systematic error termed differential code biases (DCBs). DCBs depend on both satellite and receiver, and are related to that the signal transit times in radio frequency paths of the receiver and the satellite differ for the L1 and L2 ranges, and depend on the signal frequency. This error may significantly exceed the real TEC value and lead to obtaining unphysical negative TEC values [6].To determine the absolute TEC accounting for DCBs from the data of a single GPS/GLONASS station, we have developed the following algorithm:(1) To calculate the TEC from code I p and phase I u measurements.(2) To separate data sequences into continuous-time intervals.(3) To detect and eliminate the impact of outliers and signal tracking losses in the TEC data [2]. (4) To remove the ambiguity of phase measurements:where N is the number of measurements at a continuous interval. (5) To estimate DCBs by using a simple model of measurements.The model parameters are determined based on the minimization of the standard deviation between the experimental and model data (see below). (6) To correct TEC sequences obtained in item 4 by the DCB value.We use the following model of TEC measurements:where I V is the absolute vertical TEC value; D/ is the latitude difference between the ionospheric point coordinate / and that of the / 0 station; Dl is the longitude difference between the ionospheric point coordinate l and that of the l 0 st...

Space Weather Events, Hurricanes, and Earthquakes in Mexico in September 2017

“…We used global ionospheric maps to confirm global effects, and to estimate the regional effects over Mexico we used local data. Receiver‐independent exchange files provided by different regional networks of GPS receivers were processed by TayAbsTEC method (Mylnikova et al, ; Yasyukevich, Mylnikova, & Polyakova, ; Yasyukevich, Mylnikova, Kunitsyn, et al, ). Note that it is challenging to separate the effects of different space weather phenomena in September 2017, since several of them overlap and occurred within a few days.…”

TEC behavior over the Mexican region

“…It is known, that the mapping function influences a lot on the accuracy of the absolute vTEC estimation [Schaer et al 1998]. After analyzing mapping functions for a number of observation points using the stations of IGS network and simulations based on IRI-2012 the authors [Mylnikova and Yasyukevich 2016, Yasyukevich et al 2015a, Yasyukevich et al 2015b showed that the changes of sTEC occurred with different velocities in various regions of the Earth due to different angles of the satellite passage at different latitudes. They introduced experimentally-determined correction factors α to convert sTEC to vTEC.…”

Method of diagnosing frequency dispersion parameters for transionospheric propagation of wideband signals using GLONASS/GPS technologies

“…-estimation of the limited bandwidth of a wideband system (coherent bandwidth) for the case of operation of a communication system in a dispersive channel [5,6]; Effect of frequency dispersion cannot be completely eliminated if TEC is measured with an error. When measuring TEC based on data from navigation satellites [7], stochastic errors occur. As a result, the measured TEC value can be written as follows:…”