Reference : Measuring Total Electron Content with GNSS: Investigation of Two Different Techniques
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Measuring Total Electron Content with GNSS: Investigation of Two Different Techniques
Bidaine, Benoît mailto [Université de Liège - ULiège / FNRS > Département de géographie - Department of Geography > Unité de Géomatique - Geomatics Unit > > >]
Warnant, René mailto [Institut Royal Météorologique - IRM - Royal Meteorological Institute - RMI > > > >]
The Institution of Engineering and Technology 11th International Conference on Ionospheric Radio Systems and Techniques (IRST 2009)
Institution of Engineering and Technology - IET
11th International Conference on Ionospheric Radio Systems and Techniques (IRST 2009)
du 28 avril 2009 au 1er mai 2009
Institution of Engineering and Technology - IET
[en] Total Electron Content (TEC) ; Global Navigation Satellite Systems (GNSS) ; TEC comparison ; sTEC calibration ; Global Ionospheric Maps (GIMs)
[fr] Géodésie et GNSS
[en] The ionosphere widely affects Global Navigation Satellite Systems (GNSS) applications, inducing among others a delay in GNSS measurements. This delay is closely linked to the Total Electron Content (TEC) of the ionosphere, a major parameter which can hence be monitored using GNSS. To this extent, phase measurements are taken as a basis for their lower noise level. Levelling strategies have then to be defined for the phase measurements are obtained with an initial unknown number of cycles called ambiguity.
The most common technique, referred to as carrier-to-code levelling, consists in using the differences between code and phase measurements and their average on a continuous set of epochs. This option, chosen at the Royal Meteorological Institute (RMI) of Belgium to compute TEC for Belgian GPS stations, requires code hardware delays estimation. Another has been proposed which takes benefit from Global Ionospheric Maps (GIMs) to compute a reference TEC used for ambiguity resolution.
In order to understand the consequences of using one method or the other, we compare slant TEC data obtained from both techniques for a mid-latitude station (Brussels) during a high solar activity period (2002). We observed large differences (6.8 TECu on average) showing features apparently related to ionospheric and geomagnetic activity. We attribute these observations to a combination of effects originating in code delays estimation, multipath and noise as well as GIMs errors. We try to differentiate between these effects by focusing on several days and satellites. We concentrate for example on days presenting large TEC differences and geomagnetic disturbances simultaneously (or not) or on satellites displaying recurrent patterns on consecutive days.
Finally we highlight the impact of the choice of GIMs involved in sTEC calibration. To this extent, we analyse vertical TEC statistics showing a general underestimation from RMI data. The highest bias (5.8 TECu) is obtained for the UPC GIMs used in the second levelling technique.
Researchers ; Professionals
The authors acknowledge the IET for copyright and source.

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