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Assessment of GPS data for meteorological applications over Africa: Study of error sources and analysis of positioning accuracy / Andrea Walpersdorf in Journal of Atmospheric and Solar-Terrestrial Physics, vol 69 n° 12 (August 2007)  

Public [article]  inJournal of Atmospheric and Solar-Terrestrial Physics > vol 69 n° 12 (August 2007) . - pp 1312 - 1330 Titre : Assessment of GPS data for meteorological applications over Africa: Study of error sources and analysis of positioning accuracy Type de document : Article/Communication Auteurs : Andrea Walpersdorf, Auteur ; Marie-Noëlle Bouin , Auteur ; Olivier Bock , Auteur ; Erik Doerflinger, Auteur Année de publication : 2007 Article en page(s) : pp 1312 - 1330 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Afrique tropicale [Termes IGN] données météorologiques [Termes IGN] mousson [Termes IGN] précision du positionnement [Termes IGN] retard troposphérique zénithal [Termes IGN] vapeur d'eau Résumé : (auteur) The aim of this study is to assess the availability and quality of data from the International GNSS Service (IGS) Global Positioning System (GPS) network in Africa, especially for retrieving zenith tropospheric delay (ZTD), from which precipitable water vapour (PWV) can be derived, in view of application to the African Monsoon Multidisciplinary Analysis (AMMA) project. Three major error sources for the GPS data analysis evaluating PWV in Africa are the accuracy of the satellite orbits, the correction for the radio delay induced by the ionosphere and the vertical site displacements due to ocean loading. The first part of this study examines these error sources and the validity of GPS data for meteorological applications in Africa in dedicated analyses spanning the year 2001. These analyses were performed using the IGS precise orbits. Weak degradation of baseline precision with increasing baseline lengths suggests that the average orbital error is not limiting the GPS analysis in Africa. The impact of the ionosphere has been evaluated during a maximum of solar activity in 2001. The loss of L2 data has actually been observed. It amounts to 2% on average for 2001, with maxima of 8% during magnetic storm events. A slight decrease in formal accuracy of ZTD seems to be related to the loss of L2 data at the end of the day. This indicates that scintillation effects are present in the GPS observations but however are not a major limitation. The impact of ocean loading is found to be significant on ZTD estimates (up to ±2 mm in equivalent PWV). The use of a proper ocean loading model eliminates this effect. The second aspect of this study concerns the IGS analysis quality for the African stations. The accuracy has been assessed through position dispersion between individual solutions and the most recent version of the IGS combined solution IGb00, and residuals from the transformation of the IGS combined solution into the International Terrestrial Reference Frame 2005. The positioning performance of the IGS analysis is consistent with an accuracy in ZTD of ±6 mm (±1 mm in PWV), as requested for meteorological applications such as planned in AMMA. Numéro de notice : A2007-672 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jastp.2007.04.008 Date de publication en ligne : 08/05/2007 En ligne : https://doi.org/10.1016/j.jastp.2007.04.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102771 [article]