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Amélioration de la justesse en nivellement par l’estimation locale des corrections normales ou orthométriques / Thomas Touzé in XYZ, n° 179 (juin 2024)

Public [article]  inXYZ > n° 179 (juin 2024) . - pp 56 - 61 Titre : Amélioration de la justesse en nivellement par l’estimation locale des corrections normales ou orthométriques Type de document : Article/Communication Auteurs : Thomas Touzé, Auteur Année de publication : 2024 Article en page(s) : pp 56 - 61 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] correction des altitudes [Termes IGN] correction orthométrique [Termes IGN] dénivelée [Termes IGN] gravimètre [Termes IGN] nivellement Résumé : Le problème du nivellement, c’est de savoir comment déduire des accroissements élémentaires de hauteur, mesurés sur le terrain au niveau, les accroissements respectifs des altitudes. En toute rigueur, d’un côté, il faut tenir compte de la pesanteur réelle à la surface de la Terre tandis que de l’autre, on a la pesanteur conventionnelle moyenne servant à la définition des altitudes. Or, si le rapport entre ces deux pesanteurs est très proche de 1, il n’en est pas égal en général. À défaut de recommander l’acquisition d’un gravimètre, nous proposons dans cet article une méthode valable localement permettant d’exprimer les corrections normales et orthométriques des dénivelées géométriques. Une validation expérimentale de ce modèle est d’autant plus souhaitable que le modèle proposé dans le cas des altitudes normales serait tout à fait efficace pour tirer profit des données gravimétriques actuellement disponibles en France afin d’améliorer la justesse des nivellements, grâce à un simple calcul automatisable. Numéro de notice : A2024-17903 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtSansCL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103659 [article]

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112-2024021	RAB	Revue	Centre de documentation	En réserve L003	Exclu du prêt

Iterative data assimilation approach for the refinement of marine geoid models using sea surface height and dynamic topography datasets / Sander Varbla in Journal of geodesy, vol 97 n° 3 (March 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 3 (March 2023) . - n° 24 Titre : Iterative data assimilation approach for the refinement of marine geoid models using sea surface height and dynamic topography datasets Type de document : Article/Communication Auteurs : Sander Varbla, Auteur ; Artu Ellmann, Auteur Année de publication : 2023 Article en page(s) : n° 24 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] collocation par moindres carrés [Termes IGN] données altimétriques [Termes IGN] geoïde marin [Termes IGN] hauteurs de mer [Termes IGN] itération [Termes IGN] levé gravimétrique [Termes IGN] simulation hydrodynamique Résumé : (auteur) The modelling errors of marine geoid models may reach up to a few decimetres in the shorter wavelength spectrum due to gravity data void areas and/or inaccurate data. Various data acquisition methods can provide sea surface heights more accurately. Similarly, hydrodynamic model data in conjunction with tide gauge readings allow the derivation of reliable dynamic topography. Geometrical marine geoid heights, independent of the usual gravity-based marine geoid models, can be obtained by removing the estimated dynamic topography from sea surface height measurements. This study exploits such geometry information to refine marine geoid models. A data assimilation approach was developed that iteratively combines sea surface height and dynamic topography datasets with an initial gravimetric geoid model. A case study is presented using sea surface heights from shipborne GNSS campaigns and an airborne laser scanning survey for refining the EIGEN-6C4 global geopotential model. Comparisons with a high-resolution regional marine geoid model reveal that the initial discrepancies of up to around two decimetres reduce to sub-decimetre within the study area. It is concluded that the developed iterative data assimilation approach can significantly improve the accuracy of marine geoid models, especially in regions where gravity data are of poor quality or unavailable. Numéro de notice : A2023-157 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01711-7 Date de publication en ligne : 15/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01711-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102846 [article]

Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations / Xulei Jin in Journal of geodesy, vol 97 n° 3 (March 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 3 (March 2023) . - n° 27 Titre : Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations Type de document : Article/Communication Auteurs : Xulei Jin, Auteur ; Shuli Song, Auteur Année de publication : 2023 Article en page(s) : n° 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] carte ionosphérique mondiale [Termes IGN] données Jason [Termes IGN] modèle ionosphérique [Termes IGN] temps réel [Termes IGN] teneur totale en électrons [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) For the purposes of routinely providing reliable and low-latency Global Ionosphere Maps (GIMs), a method of estimating hourly updated near real-time GIM with a time latency of about 1–2 h based on a 24-h data sliding window of Global Navigation Satellite System (GNSS) near real-time observations and real-time data streams was presented. On the basis of the implementation of near real-time GIM estimation, an hourly updated GIM nowcasting method was further proposed to improve the accurate of short-term total electron content (TEC) prediction. We estimated the Shanghai Astronomical Observatory near real-time GIM (SHUG) and nowcasting GIM (SHPG) in the solar relatively active year (2014) and quiet year (2021), and employed GIMs provided by the International GNSS Service, the Global Positioning System (GPS) differential slant TECs (dSTECs) extracted from global independent GNSS stations, and the vertical TECs (VTECs) inverted from satellite altimetry as the references to validate the estimated results. The GPS dSTECs evaluation results show that SHUG behaves fairly consistent with the rapid GIMs, with a discrepancy of less than 1 TEC unit (TECu) overall. The standard deviations (STDs) of SHUG with respect to Jason-2/-3 VTECs are no more than 10% over the majority of rapid GIMs due to the instability of observations. The performance of 1-h nowcasting SHPG is significantlybetter than the Center for Orbit Determination in Europe (CODE) 1-day predicted GIM (C1PG). GPS dSTEC validation results indicate that 1-h nowcasting SHPG is 1 to 2 TECu more reliable than C1PG in eventful ionospheric electron activity regions, and it outperforms the C1PG by 10% overall versus Jason-2/-3 VTECs. The hourly updated SHUG and SHPG have relatively high reliability and low time latency, and thus can provide excellent service for (near) real-time users and offer more accurate TEC background information than daily predicted GIM for real-time GIM estimation. Numéro de notice : A2023-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01715-3 Date de publication en ligne : 20/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01715-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102950 [article]

Coastal GNSS-R phase altimetry based on the combination of L1 and L5 signals under high sea states / Yunqiao He in Journal of geodesy, vol 97 n° 2 (February 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 2 (February 2023) . - n° 19 Titre : Coastal GNSS-R phase altimetry based on the combination of L1 and L5 signals under high sea states Type de document : Article/Communication Auteurs : Yunqiao He, Auteur ; Fan Gao, Auteur ; Tianhe Xu, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 19 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] diffusion de Rayleigh [Termes IGN] hauteurs de mer [Termes IGN] niveau de la mer [Termes IGN] phase GNSS [Termes IGN] précision altimétrique [Termes IGN] Quasi-Zenith Satellite System [Termes IGN] rapport signal sur bruit [Termes IGN] récepteur bifréquence [Termes IGN] réflectométrie par GNSS [Termes IGN] signal GNSS [Vedettes matières IGN] Altimétrie Résumé : (auteur) High-precision sea surface heights retrieved from the Global Navigation Satellite System Reflectometry (GNSS-R) measurements will be valuable in the fields of geodesy and oceanography studies. Due to the short wavelengths and low power of GNSS signals, the continuously tracked carrier phase measurements of reflected signals are usually unavailable for sea surfaces with big roughness, varying over space and time. In coastal conditions, persisting spatial coherence assumption can be made within the antenna coverage when the waves are not greatly breaking. To deal with temporal incoherence, we propose an improved algorithm to extract the combined interferometric phase difference measurements between direct and reflected signals under high sea states. After initial tracking the direct signals, dual-frequency observations are combined in the complex domain and the resulting interferometric signal is refined through open-loop tracking with 60-s coherent integration before the phase difference measurements are extracted, without tracking their respective carrier phase measurements in advance. In order to verify our method, a coastal experiment under different sea conditions was conducted and raw intermediate frequency data were collected. The raw data were then processed by a GNSS-R software-defined receiver to compute the path delay measurements of Quasi-Zenith Satellite System signals, which had good visibility during our experiment. For high sea states, that is, when the Rayleigh criterion is not fulfilled for the individual wavelengths, the phase delay measurements of L1 and L5 were random over time, while phase delay can still be well recovered for their combination. Also, the phase delay combination can be well extracted with a higher elevation angle than the previous studies. Finally, the altimetry solutions derived from the carrier phase delay measurements combination were compared with the in situ observations from a 26-GHz radar altimeter. The results show that centimeter-level altimetry accuracy using the combined measurements of L1 and L5 can be achieved under high sea states. Numéro de notice : A2023-132 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01712-6 Date de publication en ligne : 27/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01712-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102675 [article]

The ULR-repro3 GPS data reanalysis and its estimates of vertical land motion at tide gauges for sea level science / Médéric Gravelle in Earth System Science Data, vol 15 n° 1 (2023)  

Public [article]  inEarth System Science Data > vol 15 n° 1 (2023) . - pp 497 - 509 Titre : The ULR-repro3 GPS data reanalysis and its estimates of vertical land motion at tide gauges for sea level science Type de document : Article/Communication Auteurs : Médéric Gravelle, Auteur ; Guy Wöppelmann , Auteur ; Kevin Gobron, Auteur ; Zuheir Altamimi , Auteur ; Mikaël Guichard, Auteur ; Thomas Herring, Auteur ; Paul Rebischung , Auteur Année de publication : 2023 Article en page(s) : pp 497 - 509 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données marégraphiques [Termes IGN] littoral [Termes IGN] série temporelle [Termes IGN] système d'observation du niveau des eaux littorales SONEL [Termes IGN] vitesse de déplacement Résumé : (auteur) A new reanalysis of GNSS data at or near tide gauges worldwide was produced by the university of La Rochelle (ULR) group within the 3rd International GNSS Service (IGS) reprocessing campaign (repro3). The new solution, called ULR-repro3, complies with the IGS standards adopted for repro3, implementing advances in data modelling and corrections since the previous reanalysis campaign, and extending the average record length by about 7 years. The results presented here focus on the main products of interest for sea level science, that is, the station position time series and associated velocities on the vertical component at tide gauges. These products are useful to estimate accurate vertical land motion at the coast and supplement data from satellite altimetry or tide gauges for an improved understanding of sea level changes and their impacts along coastal areas. To provide realistic velocity uncertainty estimates, the noise content in the position time series was investigated considering the impact of non-tidal atmospheric loading. Overall, the ULR-repro3 position time series show reduced white noise and power-law amplitudes and station velocity uncertainties compared to the previous reanalysis. The products are available via SONEL (https://doi.org/10.26166/sonel_ulr7a; Gravelle et al., 2022). Numéro de notice : A2023-079 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/essd-15-497-2023 Date de publication en ligne : 01/02/2023 En ligne : https://doi.org/10.5194/essd-15-497-2023 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102521 [article]

L’altimétrie radar remonte les fleuves / Laurent Polidori in Géomètre, n° 2209 (janvier 2023)

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Mitigating the risk of wind damage at the forest landscape level by using stand neighbourhood and terrain elevation information in forest planning / Roope Ruotsalainen in Forestry, an international journal of forest research, vol 96 n° 1 (January 2023)  

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Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach / Mohammad-Hadi Rezvani in Journal of geodesy, vol 96 n° 12 (December 2022)  

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Improving accuracy of local geoid model using machine learning approaches and residuals of GPS/levelling geoid height / Mosbeh R. Kaloop in Survey review, vol 54 n° 387 (November 2022)  

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Tidal level prediction using combined methods of harmonic analysis and deep neural networks in Southern coastline of Iran / Kourosh Shahryari Nia in Marine geodesy, vol 45 n° 6 (November 2022)  

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Determination of local geometric geoid model for Kuwait / Ahmed Zaki in Journal of applied geodesy, vol 16 n° 4 (October 2022)  

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The use of gravity data to determine orthometric heights at the Hong Kong territories / Albertini Nsiah Ababio in Journal of applied geodesy, vol 16 n° 4 (October 2022)  

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Le cheminement du douzième parallèle (deuxième partie) : article tiré de Jalon, bulletin de l’association des personnels retraités de l’IGN, n° 146-bis de mai 2022 / Jean-Claude Leblanc in XYZ, n° 172 (septembre 2022)

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A high-resolution gravimetric geoid model for Kingdom of Saudi Arabia / Ahmed Zaki in Survey review, vol 54 n° 386 (September 2022)  

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Determination of vertical land movements through the integration of tide gauge observations and satellite altimetry data at the Brazilian Vertical Datum from 2002 to 2015 / Samoel Gehl in Boletim de Ciências Geodésicas, vol 28 n° 2 ([01/07/2022])  

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