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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]

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)  

Public [article]  inMarine geodesy > vol 45 n° 6 (November 2022) . - pp 645 - 669 Titre : Tidal level prediction using combined methods of harmonic analysis and deep neural networks in Southern coastline of Iran Type de document : Article/Communication Auteurs : Kourosh Shahryari Nia, Auteur ; Mohammad Ali Sharifi, Auteur ; Saeed Farzaneh, Auteur Année de publication : 2022 Article en page(s) : pp 645 - 669 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse harmonique [Termes IGN] classification par Perceptron multicouche [Termes IGN] classification par réseau neuronal convolutif [Termes IGN] classification par réseau neuronal récurrent [Termes IGN] données marégraphiques [Termes IGN] Iran [Termes IGN] marée océanique [Termes IGN] modèle de simulation [Termes IGN] niveau de la mer [Vedettes matières IGN] Altimétrie Résumé : (auteur) Predicting tides and water levels had always been such an important topic for researchers and professionals since the study of tidal level has pivotal role in supporting marine economy, port construction projects and maritime transportation. Tidal water levels are a combination of astronomical (deterministic part) and non-astronomical (stochastic part) water levels. In this study, we combined Harmonic Analysis (HA) with three Deep Neural Networks (DNNs), namely the Long-Short Term Memory (LSTM), Convolution Neural Network (CNN), and Multilayer Perceptron (MLP). The HA method is used for predicting the astronomical components, while DNNs are used to predict the non-astronomical water level. We have used tide gauge data from three stations along the southern coastline of Iran to demonstrate the effectiveness and accuracy of our model. We utilized RMSE, MAE, R2 (r-squared), and MAPE to evaluate the performance of the model. Finally, The LSTM network shown superior performance in most of the cases, although other networks also show good results. All three DNNs have R2 of 0.99, and the RMSE, MAE, and MAPE indicate that errors are low. Numéro de notice : A2022-783 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2022.2116615 Date de publication en ligne : 28/08/2022 En ligne : https://doi.org/10.1080/01490419.2022.2116615 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101880 [article]

Effects of offsets and outliers on the sea level trend at Antalya 2 tide gauge within the Eastern Mediterranean Sea / Mehmet Emin Ayhan in Marine geodesy, vol 45 n° 4 (July 2022)  

Public [article]  inMarine geodesy > vol 45 n° 4 (July 2022) . - pp 329 - 359 Titre : Effects of offsets and outliers on the sea level trend at Antalya 2 tide gauge within the Eastern Mediterranean Sea Type de document : Article/Communication Auteurs : Mehmet Emin Ayhan, Auteur Année de publication : 2022 Article en page(s) : pp 329 - 359 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] autocorrélation [Termes IGN] compensation [Termes IGN] données marégraphiques [Termes IGN] Méditerranée, mer [Termes IGN] modèle statistique [Termes IGN] niveau de la mer [Termes IGN] niveau moyen des mers [Termes IGN] Turquie [Termes IGN] valeur aberrante [Termes IGN] variation saisonnière [Vedettes matières IGN] Altimétrie Résumé : (auteur) Antalya 2 tide gauge (TG) station is located on the coast of Turkey within the Eastern Mediterranean Sea. Relative sea level trends 6.0 ± 1.5 and 6.44 ± 0.45 mm/year over 1985–2009 at Antalya 2 TG are different from the trend (1.6 ± 1.5 mm/year over 1935–1977) at Antalya TG within 10 km. In order to investigate this trend discrepancy, the monthly mean series at Antalya 2 TG is re-analyzed for offsets, outliers and trend estimation. The Zivot-Andrews method and the Qp outlier test result in one offset at 1994.0417 year with magnitude of 71.24 ± 13.48 mm and nine outliers. The series, corrected for the offset and outliers, de-seasonalized and filled for missed points, is identified as trend-stationary process and analyzed for trend estimation by various models. The optimal model providing the lowest Akaike Information Criteria is polynomial linear trend with multiplicative seasonal Autoregressive Moving Average (ARMA(2,0)x(1,0)12). The estimated relative sea level trend by the optimal model is 1.77 ± 0.65 mm/year. The large trend discrepancy at Antalya 2 TG is accounted for by one offset primarily (∼71%) and nine outliers (∼3%). Numéro de notice : A2022-516 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2022.2047843 Date de publication en ligne : 11/03/2022 En ligne : https://doi.org/10.1080/01490419.2022.2047843 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101064 [article]

On the consistency of coastal sea-level measurements in the Mediterranean Sea from tide gauges and satellite radar altimetry / Sara Bruni in Journal of geodesy, vol 96 n° 6 (June 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 6 (June 2022) . - n° 41 Titre : On the consistency of coastal sea-level measurements in the Mediterranean Sea from tide gauges and satellite radar altimetry Type de document : Article/Communication Auteurs : Sara Bruni, Auteur ; Luciana Fenoglio, Auteur ; Fabio Raicich, Auteur ; Susanna Zerbini, Auteur Année de publication : 2022 Article en page(s) : n° 41 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] cohérence des données [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données altimétriques [Termes IGN] données marégraphiques [Termes IGN] Méditerranée, mer [Termes IGN] niveau de la mer Résumé : (auteur) We assess the consistency of sea-level variability derived from tide-gauge (TG) and satellite radar altimeter (ALT) data acquired along the coasts of the Mediterranean Sea. For a coherent comparison between these techniques, we use GNSS observations to characterize the local vertical land movement embedded in TG records, but not affecting ALT data. We first investigate the performance of CMEMS, a gridded altimeter product covering the period 1993–2019. TG and GNSS series are not required to cover the whole altimeter period. The inter-technique comparison reveals good agreement at annual and semi-annual scales, but also the occasional occurrence of nonlinear discrepancies impacting trend estimation. Large-scale patterns of variability are observed in the Ionian region and along the continental shores from the Alboran to the Adriatic Sea. The estimates of linear trends based on TG + GNSS or CMEMS observations are found consistent within 1σ at 27/45 sites, with the best agreement in the Western Mediterranean and Adriatic Seas. We also consider the X-TRACK/ALES altimeter dataset, provided along the tracks of the Jason missions (2002–2018) and optimized for coastal applications. In this case, we identify only 12 sites suitable for the comparison. The results show that inter-technique consistency is impacted by the length of the series used in the comparison. Optimum agreement between X-TRACK/ALES and TG + GNSS trends is reached at the two sites closer to a satellite track. However, we find sites where X-TRACK/ALES-derived sea-level trends present suspicious along-track variations at  Numéro de notice : A2022-452 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s00190-022-01626-9 En ligne : http://dx.doi.org/10.1007/s00190-022-01626-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100976 [article]

Validating a new GNSS-based sea level instrument (CalNaGeo) at Senetosa Cape / Pascal Bonnefond in Marine geodesy, vol 45 n° 2 (March 2022)  

Public [article]  inMarine geodesy > vol 45 n° 2 (March 2022) . - pp 121 - 150 Titre : Validating a new GNSS-based sea level instrument (CalNaGeo) at Senetosa Cape Type de document : Article/Communication Auteurs : Pascal Bonnefond, Auteur ; Olivier Laurain, Auteur ; Pierre Exertier, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 121 - 150 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] altimétrie satellitaire par radar [Termes IGN] carte bathymétrique [Termes IGN] Corse [Termes IGN] étalonnage d'instrument [Termes IGN] geoïde marin [Termes IGN] hauteurs de mer [Termes IGN] instrument de géodésie [Termes IGN] marégraphe [Termes IGN] niveau de la mer [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] surface de la mer Résumé : (auteur) The geodetic Corsica site was set up in 1998 in order to perform altimeter calibration of the TOPEX/Poseidon (T/P) mission and subsequently, Jason-1, OSTM/Jason-2, Jason-3 and more recently Sentinel-6 Michael Freilich (launched on November, 21 2020). The aim of the present study held in June 2015 is to validate a recently developed GNSS-based sea level instrument (called CalNaGeo) that is designed with the intention to map Sea Surface Heights (SSH) over large areas. This has been undertaken using the well-defined geodetic infrastructure deployed at Senetosa Cape, and involved the estimation of the stability of the waterline (and thus the instantaneous separation of a GNSS antenna from water level) as a function of the velocity at which the instrument is towed. The results show a largely linear relationship which is approximately 1 mm/(m/s) up to a maximum practical towing speed of ∼10 knots (∼5 m/s). By comparing to the existing “geoid” map, it is also demonstrated that CalNaGeo can measure a sea surface slope with a precision better than 1 mm/km (∼2.5% of the physical slope). Different processing techniques are used and compared including GNSS Precise Point Positioning (PPP, where the goal is to extend SSH mapping far from coastal GNSS reference stations) showing an agreement at the 1-2 cm level. Numéro de notice : A2022-212 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2021.2013355 Date de publication en ligne : 28/12/2021 En ligne : https://doi.org/10.1080/01490419.2021.2013355 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100046 [article]

Applications and challenges of GRACE and GRACE follow-on satellite gravimetry / Jianli Chen in Surveys in Geophysics, vol 43 n° 1 (February 2022)  

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Apport des nouveaux systèmes GNSS de cartographie du niveau marin à l’exploitation des données altimétriques en zone côtière / Clémence Chupin (2022)  

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Cartographie dynamique de la topographie de l'océan de surface par assimilation de données altimétriques / Florian Le Guillou (2022)  

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Contraintes observationnelles historiques sur la sensibilité climatique : implications pour les projections de la hausse du niveau de la mer / Jonathan Chenal (2022)  

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Global glacier mass change by spatiotemporal analysis of digital elevation models / Romain Hugonnet (2022)  

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Non-tidal loading of the Baltic Sea in Latvian GNSS time series / Diana Haritonova in Journal of applied geodesy, vol 15 n° 4 (October 2021)  

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Establishing vertical separation models for vulnerable coastlines in developing territories / Cassandra Nanlal in Marine geodesy, vol 44 n° 5 (September 2021)  

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L’Association des amis du marégraphe de Marseille / Alain Coulomb in XYZ, n° 166 (mars 2021)

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Assessment of mass-induced sea level variability in the Tropical Indian Ocean based on GRACE and altimeter observations / Shiva Shankar Manche in Journal of geodesy, vol 95 n° 2 (February 2021)  

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Geodetic sciences / Bihter Erol (2021)  

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