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Validating the impact of various ionosphere correction on mid to long baselines and point positioning using GPS dual-frequency receivers / Alaa A. Elghazouly in Journal of applied geodesy, vol 16 n° 2 (April 2022)
[article]
Titre : Validating the impact of various ionosphere correction on mid to long baselines and point positioning using GPS dual-frequency receivers Type de document : Article/Communication Auteurs : Alaa A. Elghazouly, Auteur ; Mohamed Doma, Auteur ; Ahmed Sedeek, Auteur Année de publication : 2022 Article en page(s) : pp 81 - 90 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] correction ionosphérique
[Termes IGN] ligne de base
[Termes IGN] modèle ionosphérique
[Termes IGN] positionnement ponctuel précis
[Termes IGN] récepteur bifréquence
[Termes IGN] récepteur GPS
[Termes IGN] tempête magnétique
[Termes IGN] teneur verticale totale en électronsRésumé : (auteur) Due to the ionosphere delay, which has become the dominant GPS error source, it is crucial to remove the ionospheric effect before estimating point coordinates. Therefore, different agencies started to generate daily Global Ionosphere Maps (GIMs); the Vertical Total Electron Content (VTEC) values represented in GIMs produced by several providers can be used to remove the ionosphere error from observations. In this research, an analysis will be carried with three sources for VTEC maps produced by the Center for Orbit Determination in Europe (CODE), Regional TEC Mapping (RTM), and the International Reference Ionosphere (IRI). The evaluation is focused on the effects of a specific ionosphere GIM correction on the precise point positioning (PPP) solutions. Two networks were considered. The first network consists of seven Global Navigation Satellite Systems (GNSS) receivers from (IGS) global stations. The selected test days are six days, three of them quiet, and three other days are stormy to check the influence of geomagnetic storms on relative kinematic positioning solutions. The second network is a regional network in Egypt. The results show that the calculated coordinates using the three VTEC map sources are far from each other on stormy days rather than on quiet days. Also, the standard deviation values are large on stormy days compared to those on quiet days. Using CODE and RTM IONEX file produces the most precise coordinates after that the values of IRI. The elimination of ionospheric biases over the estimated lengths of many baselines up to 1000 km has resulted in positive findings, which show the feasibility of the suggested assessment procedure. Numéro de notice : A2022-250 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2021-0040 Date de publication en ligne : 27/11/2021 En ligne : https://doi.org/10.1515/jag-2021-0040 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100203
in Journal of applied geodesy > vol 16 n° 2 (April 2022) . - pp 81 - 90[article]Assessing ZWD models in delay and height domains using data from stations in different climate regions / Thainara Munhoz Alexandre de Lima in Applied geomatics, vol 14 n° 1 (March 2022)
[article]
Titre : Assessing ZWD models in delay and height domains using data from stations in different climate regions Type de document : Article/Communication Auteurs : Thainara Munhoz Alexandre de Lima, Auteur ; Marcelo Santos, Auteur ; Daniele Barroca Marra Alves, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 93 - 103 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] climat
[Termes IGN] correction du signal
[Termes IGN] données GNSS
[Termes IGN] modèle atmosphérique
[Termes IGN] modèle empirique
[Termes IGN] modèle météorologique
[Termes IGN] positionnement ponctuel précis
[Termes IGN] prévision météorologique
[Termes IGN] radiosondage
[Termes IGN] retard troposphérique zénithalRésumé : (auteur) Global Navigation Satellite System (GNSS) has revolutionized activities involving geodetic positioning. To achieve a desired accuracy, it is essential to model the atmosphere in an appropriate way. With respect to the neutral atmosphere, the signal sent by the satellite suffers a delay when crossing this layer during its travel to the receiver on the surface, the so-called neutral atmospheric delay. Although empirical models exist, they may not be suitable to represent microclimatic variations in different regions of the globe due to peculiarities that exist in diverse areas. To minimize this limitation, correction models based on numerical weather prediction (NWP) emerge. They allow the assessment of the delay from local atmospheric parameters and the evaluation of atmospheric particularities of each region. In addition, another way to obtain neutral atmosphere delay is by making use of data from radiosondes, which measure atmospheric data at various altitude levels. The main objective of this article is to investigate the performance of different models using GNSS data collected in countries with different climatic conditions. Assessment is performed on the positioning domain using the precise point positioning (PPP) technique. The results show that the proximity between the NWP-based models and radiosondes was approximately 3 cm, and that between empirical models was 5 cm, with variations that depended on the model and the region. Regarding the impact on the height component, the difference between the accuracy of the empirical and NWP models was approximately 16 cm. Numéro de notice : A2022-219 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s12518-021-00414-y En ligne : https://doi.org/10.1007/s12518-021-00414-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100088
in Applied geomatics > vol 14 n° 1 (March 2022) . - pp 93 - 103[article]Simultaneous retrieval of selected optical water quality indicators from Landsat-8, Sentinel-2, and Sentinel-3 / Nima Pahlevan in Remote sensing of environment, vol 270 (March 2022)
[article]
Titre : Simultaneous retrieval of selected optical water quality indicators from Landsat-8, Sentinel-2, and Sentinel-3 Type de document : Article/Communication Auteurs : Nima Pahlevan, Auteur ; Brandon Smith, Auteur ; Krista Alikas, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 112860 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] analyse des mélanges spectraux
[Termes IGN] appariement d'images
[Termes IGN] apprentissage automatique
[Termes IGN] chlorophylle
[Termes IGN] classification par maximum de vraisemblance
[Termes IGN] classification par Perceptron multicouche
[Termes IGN] correction atmosphérique
[Termes IGN] données multisources
[Termes IGN] eaux côtières
[Termes IGN] image Landsat-OLI
[Termes IGN] image Sentinel-MSI
[Termes IGN] image Sentinel-OLCI
[Termes IGN] matière organique
[Termes IGN] Oregon (Etats-Unis)
[Termes IGN] qualité des eauxRésumé : (auteur) Constructing multi-source satellite-derived water quality (WQ) products in inland and nearshore coastal waters from the past, present, and future missions is a long-standing challenge. Despite inherent differences in sensors’ spectral capability, spatial sampling, and radiometric performance, research efforts focused on formulating, implementing, and validating universal WQ algorithms continue to evolve. This research extends a recently developed machine-learning (ML) model, i.e., Mixture Density Networks (MDNs) (Pahlevan et al., 2020; Smith et al., 2021), to the inverse problem of simultaneously retrieving WQ indicators, including chlorophyll-a (Chla), Total Suspended Solids (TSS), and the absorption by Colored Dissolved Organic Matter at 440 nm (acdom(440)), across a wide array of aquatic ecosystems. We use a database of in situ measurements to train and optimize MDN models developed for the relevant spectral measurements (400–800 nm) of the Operational Land Imager (OLI), MultiSpectral Instrument (MSI), and Ocean and Land Color Instrument (OLCI) aboard the Landsat-8, Sentinel-2, and Sentinel-3 missions, respectively. Our two performance assessment approaches, namely hold-out and leave-one-out, suggest significant, albeit varying degrees of improvements with respect to second-best algorithms, depending on the sensor and WQ indicator (e.g., 68%, 75%, 117% improvements based on the hold-out method for Chla, TSS, and acdom(440), respectively from MSI-like spectra). Using these two assessment methods, we provide theoretical upper and lower bounds on model performance when evaluating similar and/or out-of-sample datasets. To evaluate multi-mission product consistency across broad spatial scales, map products are demonstrated for three near-concurrent OLI, MSI, and OLCI acquisitions. Overall, estimated TSS and acdom(440) from these three missions are consistent within the uncertainty of the model, but Chla maps from MSI and OLCI achieve greater accuracy than those from OLI. By applying two different atmospheric correction processors to OLI and MSI images, we also conduct matchup analyses to quantify the sensitivity of the MDN model and best-practice algorithms to uncertainties in reflectance products. Our model is less or equally sensitive to these uncertainties compared to other algorithms. Recognizing their uncertainties, MDN models can be applied as a global algorithm to enable harmonized retrievals of Chla, TSS, and acdom(440) in various aquatic ecosystems from multi-source satellite imagery. Local and/or regional ML models tuned with an apt data distribution (e.g., a subset of our dataset) should nevertheless be expected to outperform our global model. Numéro de notice : A2022-126 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1016/j.rse.2021.112860 Date de publication en ligne : 04/01/2022 En ligne : https://doi.org/10.1016/j.rse.2021.112860 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99705
in Remote sensing of environment > vol 270 (March 2022) . - n° 112860[article]A multipath and thermal noise joint error characterization and exploitation for low-cost GNSS PVT estimators in urban environment / Eustachio Roberto Matera (2022)
Titre : A multipath and thermal noise joint error characterization and exploitation for low-cost GNSS PVT estimators in urban environment Type de document : Thèse/HDR Auteurs : Eustachio Roberto Matera, Auteur ; Carl Milner, Directeur de thèse ; Axel Javier Garcia Pena, Directeur de thèse Editeur : Toulouse : Université de Toulouse Année de publication : 2022 Importance : 348 p. Format : 21 x 30 cm Note générale : Bibliographie
Thèse en vue de l'obtention du Doctorat de l'Université de Toulouse délivré par l'Institut National Polytechnique de Toulouse en Informatique et TélécommunicationLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] bruit thermique
[Termes IGN] correction du trajet multiple
[Termes IGN] corrélation temporelle
[Termes IGN] filtre de Kalman
[Termes IGN] rapport signal sur bruit
[Termes IGN] récepteur GNSS
[Termes IGN] signal GPS
[Termes IGN] trajet multiple
[Termes IGN] zone urbaine denseIndex. décimale : THESE Thèses et HDR Résumé : (auteur) Achieving an accurate localization is a significant challenge for low-cost GNSS devices in dense urban areas. The main limitations are encountered in the urban canyons, consisting in a reduced satellite signal availability and a positioning estimation error due to the impact of Line-of-Sight and Non Line-of-Sight multipath phenomenon. This PhD study allows to understand the impact of the multipath phenomenon on the low-cost GNSS receivers and to prove the need of accurate assessment of the multipath error model affecting the GNSS measurements, especially in urban environment. It consists in the investigation, characterization, and finally, exploitation of the multipath error components affecting the pseudorange and pseudorange-rate measurements, of a single frequency, dual constellation GNSS receiver in the urban environment, operating with GPS L1 C/A and Galileo E1 OS signals. The first goal consists in providing a set of methodologies able to identify, isolate and characterize the multipath error components from the measurements under test. However, considering that the isolation of the multipath error is a complex operation due to the superimposed effects of multipath and thermal noise, the final method consists of isolating the joint contribution of multipath and thermal noise components. The isolated multipath and thermal noise error components are firstly classified depending the corresponding received signal /0 values, and, secondly, statistically characterized by means of Probability Density Function, sample mean and sample variance. Also, the temporal and spatial correlation properties of the isolated error components are calculated by means of a methodology which estimates the temporal correlations as a function of the receiver speed. In addition, an image processing methodology based on the application of a sky-facing fish-eye camera provides the determination of an empirical /0 threshold equal to 35 dB-Hz used to qualitatively identify the Non Line- Of-Sight and Line-Of-Sight received signal reception states. The resulting errors are characterized by a nonsymmetrical, positive biased PDF for a /0 lower than 35 dBHz, while they are characterized by a symmetrical and zero-centred PDF for a /0 higher than 35 dB-Hz. Correlation times for pseudoranges are ranged from around 5s for static and very low speed dynamics to around 1s for high-speed dynamics. Correlation times for pseudorange-rates ranged from around 0.5s for static and very low speed dynamics to around 0.2s for high-speed dynamics, due to the data-rate limitations. The second goal consists in exploiting the multipath and thermal noise error models and the LOS/NLOS received signal reception state estimation in a low-complex EKF-based architecture to improve the accuracy of the PVT estimates. This is obtained by implementing some techniques based on the measurement weighting approach to take into account the statistical properties of the error under exam and by the application of a time differenced architecture design to exploit the temporal correlation properties. Positioning performance of the tested solutions surpassed the performances of a simple EKF architecture and are comparable to the performances of a uBlox M8T receiver. Note de contenu : 1- Introduction
2- GNSS architecture
3- GNSS receiver processing
4- Multipath effects on the GNSS receiver tracking performances
5- Multipath characterization methodologies
6- Multipath characterization results
7- Proposed extended Kalman Filter Algorithm
8- Conclusions and recommandations for future worksNuméro de notice : 15272 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse française Note de thèse : Thèse de Doctorat: en Informatique et Télécommunication : Toulouse :2022 Organisme de stage : Laboratoire de Télécommunications (TELECOM-ENAC) DOI : sans En ligne : http://www.theses.fr/2022INPT0030 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100992 Preparation of the VENµS satellite data over Israel for the input into the GRASP data treatment algorithm / Maeve Blarel (2022)
Titre : Preparation of the VENµS satellite data over Israel for the input into the GRASP data treatment algorithm Type de document : Mémoire Auteurs : Maeve Blarel, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2022 Importance : 73 p. Format : 21 x 30 cm Note générale : Bibliographie
Rapport de projet pluridisciplinaire, cycle ING2Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] aérosol
[Termes IGN] conversion de données
[Termes IGN] correction atmosphérique
[Termes IGN] correction géométrique
[Termes IGN] correction radiométrique
[Termes IGN] image hyperspectrale
[Termes IGN] image Venµs-VSSC
[Termes IGN] Israël
[Termes IGN] microsatellite
[Termes IGN] Python (langage de programmation)
[Termes IGN] série temporelle
[Termes IGN] traitement de données localiséesIndex. décimale : PROJET Mémoires : Rapports de projet - stage des ingénieurs de 2e année Résumé : (Auteur) Réalisé au sein du laboratoire de télédétection de l’Institut Jacob Blaustein pour la recherche sur le désert (BIDR) de l’Université Ben-Gourion du Négev, en Israël, et financé par une mission du CNRS, ce stage a pour objectif l’adaptation d’un driver dédié à la conversion des données satellites VENµS et à leur préparation pour le traitement par l’algorithme GRASP. VENµS (Vegetation and Environment monitoring New Micro-Satellite) est un microsatellite, fruit d’une collaboration franco-israélienne pour l’observation de la Terre à l’aide d’une caméra super spectrale. Les visées de la mission scientifique sont déterminées par le CESBIO et le CNES, en France, et l’Université Ben-Gourion du Néguev, en Israël. Son objectif est de fournir des observations à haute résolution spatiale pour la recherche scientifique portant sur la surveillance, l’analyse et la caractérisation du fonctionnement de la surface terrestre, sous les effets de facteurs environnementaux et des activités humaines. Plus particulièrement, ces données sont dédiées à des applications dans l’agriculture de précision, l’urbanisation et la surveillance des masses d’eau. Les images acquises au-dessus d’Israël ont un format différent de celles prises à travers le monde pour une gestion distincte des données. Aujourd’hui, les recherches israélienne et française souhaitent une caractérisation des aérosols atmosphériques sur Israël et un traitement des données par GRASP. La problématique rencontrée est la conversion des données sur Israël pour leur entrée dans cet algorithme. Après une phase de découverte et de compréhension des données satellites VENµS et celles requises à l’entrée de GRASP, le travail de ce présent stage consiste à développer une solution d’adaptation du programme informatique pour la conversion des données VENµS sur Israël. Des perspectives existent pour ce projet. Pour observer la Terre, on souhaite des données de plus en plus précises par des améliorations de l’acquisition et du traitement des images. Concernant l’acquisition de données, les intervalles de temps de revisite limitent actuellement l’avantage multi-pixel. D’un autre côté, l’un des objectifs de cette mission satellitaire est le développement des algorithmes pour exploiter des séries temporelles de données, incluant les corrections géométriques et radiométriques. Pour GRASP, la gestion du masque des nuages doit être perfectionnée et concernant le driver adapté, les observations directionnelles demandent une exploitation plus grande. L’ensemble des codes Python, fonctionnels et commentés, implémenté au cours du stage est confidentiel et reste à la propriété de GRASP. Par conséquent, aucun script provenant du code source ne sera présenté au cours de ce rapport. Note de contenu : Introduction
1. Internship presentation
1.1 Context
1.2 Issues and Objectives
1.3 State of current research
2. Technical study
2.1 Driver architecture
2.2 Language, libraries and software in use
2.3 The data
3. Achievement
3.1 Implementation
3.2 Progress of internship
3.3 Difficulties encountered and Solutions adopted
ConclusionNuméro de notice : 26872 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Mémoire de projet pluridisciplinaire Organisme de stage : Laboratoire de télédétection de l’Institut Jacob Blaustein (Université Ben-Gourion du Négev) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101702 Documents numériques
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Preparation of the VENµS satellite data over Israel for the input into the GRASP data treatment algorithm - pdf auteurAdobe Acrobat PDF Ionospheric corrections tailored to the Galileo High Accuracy Service / Adria Rovira-Garcia in Journal of geodesy, vol 95 n° 12 (December 2021)PermalinkIonospheric tomographic common clock model of undifferenced uncombined GNSS measurements / German Olivares-Pulido in Journal of geodesy, vol 95 n° 11 (November 2021)PermalinkField scale wheat LAI retrieval from multispectral Sentinel 2A-MSI and LandSat 8-OLI imagery: effect of atmospheric correction, image resolutions and inversion techniques / Rajkumar Dhakar in Geocarto international, vol 36 n° 18 ([01/10/2021])PermalinkTropospheric and range biases in Satellite Laser Ranging / Mateusz Drożdżewski in Journal of geodesy, vol 95 n° 9 (September 2021)PermalinkInteger-estimable FDMA model as an enabler of GLONASS PPP-RTK / Baocheng Zhang in Journal of geodesy, vol 95 n° 8 (August 2021)PermalinkAtmospheric correction to passive microwave brightness temperature in snow cover mapping over china / Yubao Qiu in IEEE Transactions on geoscience and remote sensing, vol 59 n° 8 (August 2021)PermalinkMulti-GNSS PPP/INS tightly coupled integration with atmospheric augmentation and its application in urban vehicle navigation / Shengfeng Gu in Journal of geodesy, vol 95 n° 6 (June 2021)PermalinkAtmospheric correction of Sentinel-3/OLCI data for mapping of suspended particulate matter and chlorophyll-a concentration in Belgian turbid coastal waters / Quinten Vanhellemont in Remote sensing of environment, Vol 256 (April 2020)PermalinkAutomatic atmospheric correction for shortwave hyperspectral remote sensing data using a time-dependent deep neural network / Jian Sun in ISPRS Journal of photogrammetry and remote sensing, vol 174 (April 2021)PermalinkImpact of atmospheric correction on spatial heterogeneity relations between land surface temperature and biophysical compositions / Xin-Ming Zhu in IEEE Transactions on geoscience and remote sensing, Vol 59 n° 3 (March 2021)Permalink