000005681 001__ 5681
000005681 005__ 20220204110729.0
000005681 0247_ $$2DOI$$a10.1016/j.asr.2021.04.008
000005681 037__ $$aSCART-2022-0039
000005681 100__ $$aMorel, Laurent
000005681 245__ $$aOn the relation between GPS tropospheric gradients and the local topography
000005681 260__ $$c2021
000005681 520__ $$aThe estimation of tropospheric gradients in GNSS data processing is a well-known technique to improve positioning precision. To study the correlation between the tropospheric gradients and the topography, we computed Zenith Wet Delay (ZWD) and tropospheric gradients using the GIPSY-OASIS II SOFTWARE from 2 years of GPS observations recorded at 52 worldwide permanent stations, focusing on regions with significant relief. We observe that gradient directions are stable over time and point towards the relief for most of the considered stations. Based on these results, we discuss the physical meaning of the tropospheric horizontal gradients and we investigate why gradients have this particular direction for stations located nearby high mountains. The GPS stations were selected and classified into four main categories: stations close to a mountain range or an isolated mountain (class 1 and 2), stations surrounded by isolated mountains in several directions or in all directions (class 3 and 4). The correlation between the gradient direction and their magnitude with respect to mountain slopes was analysed. A very clear correlation appears for stations of classes 1 and 2 whereas no correlation is obvious for stations of classes 3 and 4. For 89% of stations in classes 1 and 2, a relevant correlation appears, varying between 0.4 and 1. For 64% of stations in classes 1 and 2, a relevant correlation appears, varying between 0.6 and 1. Horizontal gradients estimation show very significant amplitude and a stable direction all along the year, this main direction is most of the time pointing towards the direction of mountains. This behaviour can be explained by a vertical shift of the tropospheric layer due to the presence of mountains, close to the station and up to the maximum distance of 60 km from the station. This orientation does not seem to depend on seasons because no annual or bimonthly means variations appear for all stations. Moreover diurnal variations do not appear on the spatial distribution of the gradients and results are similar for neighbouring stations, separated by few km, which show that local effects such as multipath propagation have influence.
000005681 594__ $$aSTCE
000005681 6531_ $$aGNSS
000005681 6531_ $$aZenith tropospheric delay
000005681 6531_ $$aZenith wet delay
000005681 6531_ $$aTropospheric gradients
000005681 700__ $$aMoudnin, Ouafae
000005681 700__ $$aDurand, Frédéric
000005681 700__ $$aNicolas, Joëlle
000005681 700__ $$aFollin, Jean-Michel
000005681 700__ $$aDurand, Stéphane
000005681 700__ $$aPottiaux, Eric
000005681 700__ $$aVan Baelen, Joël
000005681 700__ $$ade Oliveira, Paulo Sergio Jr
000005681 773__ $$c1676-1689$$n4$$pAdvances in Space Research$$v68$$y2021
000005681 8560_ $$feric.pottiaux@observatoire.be
000005681 85642 $$ahttps://www.sciencedirect.com/science/article/pii/S0273117721002933
000005681 8564_ $$s4975180$$uhttp://publi2-as.oma.be/record/5681/files/1-s2.0-S0273117721002933-main.pdf
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000005681 905__ $$apublished in
000005681 980__ $$aREFERD