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A geographic information-driven method and a new large scale dataset for remote sensing cloud/snow detection / Xi Wu in ISPRS Journal of photogrammetry and remote sensing, vol 174 (April 2021)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 174 (April 2021) . - pp 87 - 104 Titre : A geographic information-driven method and a new large scale dataset for remote sensing cloud/snow detection Type de document : Article/Communication Auteurs : Xi Wu, Auteur ; Zhenwei Shi, Auteur ; Zhengxia Zou, Auteur Année de publication : 2021 Article en page(s) : pp 87 - 104 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] altitude [Termes IGN] apprentissage profond [Termes IGN] classification par réseau neuronal convolutif [Termes IGN] détection des nuages [Termes IGN] extraction de traits caractéristiques [Termes IGN] fusion de données [Termes IGN] image Gaofen [Termes IGN] information géographique [Termes IGN] latitude [Termes IGN] longitude [Termes IGN] modèle statistique [Termes IGN] neige [Termes IGN] Normalized Difference Snow Index Résumé : (auteur) Geographic information such as the altitude, latitude, and longitude are common but fundamental meta-records in remote sensing image products. In this paper, it is shown that such a group of records provides important priors for cloud and snow detection in remote sensing imagery. The intuition comes from some common geographical knowledge, where many of them are important but are often overlooked. For example, it is generally known that snow is less likely to exist in low-latitude or low-altitude areas, and clouds in different geographic may have various visual appearances. Previous cloud and snow detection methods simply ignore the use of such information, and perform detection solely based on the image data (band reflectance). Due to the neglect of such priors, most of these methods are difficult to obtain satisfactory performance in complex scenarios (e.g., cloud-snow coexistence). In this paper, a novel neural network called “Geographic Information-driven Network (GeoInfoNet)” is proposed for cloud and snow detection. In addition to the use of the image data, the model integrates the geographic information at both training and detection phases. A “geographic information encoder” is specially designed, which encodes the altitude, latitude, and longitude of imagery to a set of auxiliary maps and then feeds them to the detection network. The proposed network can be trained in an end-to-end fashion with dense robust features extracted and fused. A new dataset called “Levir_CS” for cloud and snow detection is built, which contains 4,168 Gaofen-1 satellite images and corresponding geographical records, and is over 20× larger than other datasets in this field. On “Levir_CS”, experiments show that the method achieves 90.74% intersection over union of cloud and 78.26% intersection over union of snow. It outperforms other state of the art cloud and snow detection methods with a large margin. Feature visualizations also show that the method learns some important priors which is close to the common sense. The proposed dataset and the code of GeoInfoNet are available in https://github.com/permanentCH5/GeoInfoNet. Numéro de notice : A2021-209 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2021.01.023 date de publication en ligne : 22/02/2021 En ligne : https://doi.org/10.1016/j.isprsjprs.2021.01.023 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97187 [article]

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Mitigating high latitude ionospheric scintillation effects on GNSS Precise Point Positioning exploiting 1-s scintillation indices / Kai Guo in Journal of geodesy, vol 95 n° 3 (March 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 3 (March 2021) . - n° 30 Titre : Mitigating high latitude ionospheric scintillation effects on GNSS Precise Point Positioning exploiting 1-s scintillation indices Type de document : Article/Communication Auteurs : Kai Guo, Auteur ; Sreeja Vadakke Veettil, Auteur ; Brian Jerald Weaver, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 30 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] Antarctique [Termes IGN] atténuation du signal [Termes IGN] Canada [Termes IGN] erreur de positionnement [Termes IGN] latitude [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur GNSS [Termes IGN] scintillation [Termes IGN] tempête magnétique Résumé : (auteur) Ionospheric scintillation refers to rapid and random fluctuations in radio frequency signal intensity and phase, which occurs more frequently and severely at high latitudes under strong solar and geomagnetic activity. As one of the most challenging error sources affecting Global Navigation Satellite System (GNSS), scintillation can significantly degrade the performance of GNSS receivers, thereby leading to increased positioning errors. This study analyzes Global Positioning System (GPS) scintillation data recorded by two ionospheric scintillation monitoring receivers operational, respectively, in the Arctic and northern Canada during a geomagnetic storm in 2019. A novel approach is proposed to calculate 1-s scintillation indices. The 1-s receiver tracking error variances are then estimated, which are further used to mitigate the high latitude scintillation effects on GPS Precise Point Positioning. Results show that the 1-s scintillation indices can describe the signal fluctuations under scintillation more accurately. With the mitigation approach, the 3D positioning error is greatly reduced under scintillation analyzed in this study. Additionally, the 1-s tracking error variance achieves a better performance in scintillation mitigation compared with the previous approach which exploits 1-min tracking error variance estimated by the commonly used 1-min scintillation indices. This work is relevant for a better understanding of the high latitude scintillation effects on GNSS and is also beneficial for developing scintillation mitigation tools for GNSS positioning. Numéro de notice : A2021-222 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01475-y date de publication en ligne : 22/02/2021 En ligne : https://doi.org/10.1007/s00190-021-01475-y Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97191 [article]

Les représentations planes cylindriques de la terre / Françoise Duquenne in XYZ, n° 157 (décembre 2018 - février 2019)

Public [article]  inXYZ > n° 157 (décembre 2018 - février 2019) . - pp 45 - 50 Titre : Les représentations planes cylindriques de la terre Type de document : Article/Communication Auteurs : Françoise Duquenne , Auteur Année de publication : 2018 Article en page(s) : pp 45 - 50 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Projections [Termes IGN] canevas de projection [Termes IGN] convergence des méridiens [Termes IGN] facteur d'échelle [Termes IGN] latitude [Termes IGN] ligne géodésique [Termes IGN] module linéaire [Termes IGN] projection cylindrique [Termes IGN] projection Universal Transverse Mercator Résumé : (auteur) The purpose of this paper is to recall th fundamental concept of the plane cylindrical representations of the earth, especially those which are conformal. Amongst these, the most known and used projection throughout the world is the Universal Transverse Mercator (UTM). The algorithm of calculation presented here, developed by French IGN, has the advantage of using exact formulas and not limited developments like many others, and thus of beeing easily computerized. Numéro de notice : A2018-534 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91579 [article]

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Characterizing noise in daily GPS position time series with overlapping Hadamard variance and maximum likelihood estimation / Chang Xu in Survey review, vol 49 n° 355 (October 2017)  

Public [article]  inSurvey review > vol 49 n° 355 (October 2017) . - pp 239 - 248 Titre : Characterizing noise in daily GPS position time series with overlapping Hadamard variance and maximum likelihood estimation Type de document : Article/Communication Auteurs : Chang Xu, Auteur ; D. Yue, Auteur Année de publication : 2017 Article en page(s) : pp 239 - 248 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] bruit (théorie du signal) [Termes IGN] bruit blanc [Termes IGN] bruit rose [Termes IGN] caractérisation [Termes IGN] Chine [Termes IGN] coordonnées GPS [Termes IGN] latitude [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] série temporelle [Termes IGN] signal aléatoire [Termes IGN] station permanente [Termes IGN] variance [Termes IGN] variance de Hadamard [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) We assess the noise characteristics of daily position time series (Jet Propulsion Laboratory global solutions) from 12 International GNSS Service sites located in China, using both overlapping Hadamard variance (OHVAR) and maximum likelihood estimation (MLE). The result shows that OHVAR is computationally cheap, and the dominate power-law noise inferred is in good agreement with the ones inferred by comparing MLE values. However, OHVAR is insufficient to assess the long-period noise characteristics [e.g., random walk noise (RW)]. From the MLE analysis, the RW contribution is likely to be present in 14% of the time series, while the noise of most sites are characterized by a combination of white and flicker (or power law) noise (i.e., FL + WH or PL + WH). Moreover, sites near the northern crest of the equatorial ionization anomaly have larger amplitudes of WH in the vertical component, while no clear latitude dependency is observed in FL amplitudes. Numéro de notice : A2017-547 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1163830 En ligne : https://doi.org/10.1080/00396265.2016.1163830 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86602 [article]

Performance evaluation of ionospheric time delay forecasting models using GPS observations at a low-latitude station / G. Sivavaraprasad in Advances in space research, vol 60 n° 2 (15 July 2017)  

Public [article]  inAdvances in space research > vol 60 n° 2 (15 July 2017) . - pp 475 - 490 Titre : Performance evaluation of ionospheric time delay forecasting models using GPS observations at a low-latitude station Type de document : Article/Communication Auteurs : G. Sivavaraprasad, Auteur ; D. Venkata Ratman, Auteur Année de publication : 2017 Article en page(s) : pp 475 - 490 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] données GPS [Termes IGN] données météorologiques [Termes IGN] Inde [Termes IGN] International Reference Ionosphere [Termes IGN] latitude [Termes IGN] modèle de simulation [Termes IGN] modèle ionosphérique [Termes IGN] retard ionosphèrique [Termes IGN] teneur totale en électrons [Termes IGN] teneur verticale totale en électrons [Termes IGN] test de performance [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Ionospheric delay is one of the major atmospheric effects on the performance of satellite-based radio navigation systems. It limits the accuracy and availability of Global Positioning System (GPS) measurements, related to critical societal and safety applications. The temporal and spatial gradients of ionospheric total electron content (TEC) are driven by several unknown priori geophysical conditions and solar-terrestrial phenomena. Thereby, the prediction of ionospheric delay is challenging especially over Indian sub-continent. Therefore, an appropriate short/long-term ionospheric delay forecasting model is necessary. Hence, the intent of this paper is to forecast ionospheric delays by considering day to day, monthly and seasonal ionospheric TEC variations. GPS-TEC data (January 2013–December 2013) is extracted from a multi frequency GPS receiver established at K L University, Vaddeswaram, Guntur station (geographic: 16.37°N, 80.37°E; geomagnetic: 7.44°N, 153.75°E), India. An evaluation, in terms of forecasting capabilities, of three ionospheric time delay models – an Auto Regressive Moving Average (ARMA) model, Auto Regressive Integrated Moving Average (ARIMA) model, and a Holt-Winter's model is presented. The performances of these models are evaluated through error measurement analysis during both geomagnetic quiet and disturbed days. It is found that, ARMA model is effectively forecasting the ionospheric delay with an accuracy of 82–94%, which is 10% more superior to ARIMA and Holt-Winter’s models. Moreover, the modeled VTEC derived from International Reference Ionosphere, IRI (IRI-2012) model and new global TEC model, Neustrelitz TEC Model (NTCM-GL) have compared with forecasted VTEC values of ARMA, ARIMA and Holt-Winter’s models during geomagnetic quiet days. The forecast results are indicating that ARMA model would be useful to set up an early warning system for ionospheric disturbances at low latitude regions. Numéro de notice : A2017-252 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2017.01.031 date de publication en ligne : 30/01/2017 En ligne : https://doi.org/10.1016/j.asr.2017.01.031 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85254 [article]

Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions / O. E. Abe in Journal of geodesy, vol 91 n° 4 (April 2017)  

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From the portolan chart to the latitude chart / Joaquim Alves Gaspar in Cartes & Géomatique, n° 216 (juin 2013)  

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Geolocation and time: an evolution of the millennial pair, Part 1 / J. Triglav in Geoinformatics, vol 12 n° 7 (01/10/2009)

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N48°26'58" : le plus long parallèle de France / K. Drame in XYZ, n° 106 (mars - mai 2006)

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Des longitudes et des mers : la genèse de la navigation (1/3) / Frédéric Bretar in XYZ, n° 102 (mars - mai 2005)

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Accuracy of the coefficient expansion of the transverse Mercator projection / E. Enriquez in International journal of geographical information science IJGIS, vol 18 n° 6 (october 2004)

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L'aventure cartographique / Jean Lefort (2004)

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Une histoire du point en mer / A. Gillet (2000)

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Collected papers of Raimundo O. Vicente on geodynamics, geodesy and astronomy / R.O. Vicente (1998)

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Astronomie / Françoise Duquenne (1997)

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