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Estimation of frequency and duration of ionospheric disturbances over Turkey with IONOLAB-FFT algorithm / Secil Karatay in Journal of geodesy, vol 94 n° 9 (September 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 9 (September 2020) . - n° 89 Titre : Estimation of frequency and duration of ionospheric disturbances over Turkey with IONOLAB-FFT algorithm Type de document : Article/Communication Auteurs : Secil Karatay, Auteur Année de publication : 2020 Article en page(s) : n° 89 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] fréquence [Termes IGN] oscillation [Termes IGN] perturbation ionosphérique [Termes IGN] récepteur bifréquence [Termes IGN] récepteur GPS [Termes IGN] teneur totale en électrons [Termes IGN] transformation rapide de Fourier [Termes IGN] Turquie Résumé : (auteur) One of the more common methods of observation of variability of the Earth’s ionosphere is based on total electron content (TEC) estimated from ground-based dual-frequency Global Positioning System (GPS) receivers. Variations in solar, geomagnetic and seismic activity cause depletions or enhancements in the ionospheric electron concentrations that can be detected as disturbances. Some of these disturbances have wave-like characteristics, where frequency of oscillation can be used to identify and classify the disturbance. In this study, the frequency of such periodic disturbances is estimated using a fast Fourier transform (FFT)-based method, namely IONOLAB-FFT, in the spectral domain. IONOLAB-FFT, which was initially developed to be used on slant TEC (STEC), is modified to be applied to TEC in the local zenith direction of the receiver. The algorithm is tested using literature data on disturbances generated by a geomagnetic activity, a solar flare, a medium-scale traveling ionospheric disturbance (MSTID), a large-scale TID (LSTID) and an earthquake. An accordance with these known disturbances is observed in running IONOLAB-FFT, and the main frequencies and durations of the disturbances are estimated. IONOLAB-FFT method is applied to TEC computed from Turkish Permanent GPS Network (TNPGN-Active) which lies in mid-latitude region to detect the any wave-like oscillations, sudden disturbances and other irregularities during December, March, June and September months for 2010, 2011 and 2012 years. It is observed that a large number of the estimated frequencies are accumulated between 0.08 and 0.14 MHz corresponding to periods of 3.5 h to 2 h. The significant frequencies are grouped less than 0.28 MHz. A large number of the durations of the oscillations are between 425 and 550 min in 2010, 300 and 550 min in 2011 and 350 and 400 min in 2012. The longest duration (around 800 min: 13.33 h) is observed in December months, and the shortest duration (around 2 h) is observed in September months. Numéro de notice : A2020-541 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01416-1 date de publication en ligne : 31/08/2020 En ligne : https://doi.org/10.1007/s00190-020-01416-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95743 [article]

The possibility of measuring the dynamic response of structures using non-contact geodetic method / Bostjan Kovacic in Geodetski vestnik, vol 63 n° 1 (March - May 2019)  

Public [article]  inGeodetski vestnik > vol 63 n° 1 (March - May 2019) . - pp 57 - 72 Titre : The possibility of measuring the dynamic response of structures using non-contact geodetic method Type de document : Article/Communication Auteurs : Bostjan Kovacic, Auteur ; Tomaž Motoh, Auteur Année de publication : 2019 Article en page(s) : pp 57 - 72 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie [Termes IGN] analyse spectrale [Termes IGN] auscultation d'ouvrage [Termes IGN] génie civil [Termes IGN] oscillation [Termes IGN] pont [Termes IGN] Python (langage de programmation) [Termes IGN] tachéomètre électronique [Termes IGN] topométrie de précision [Termes IGN] transformation rapide de Fourier Résumé : (Auteur) Building construction is the subject of various factors and their consequences must be regularly monitored; this can be carried out in the form of control measurements or monitoring. This article aims to show the usability of geodetic non-contact methods in defining the dynamic response of structures. The lamella on which various methods for monitoring the dynamic response was used for simulation; the emphasis is on a modern geodetic method using a Robotic Total Station (RTS). To determine the dynamic response, the algorithm for the determination of the harmonic oscillation´s average amplitude and the methods of the spectral analysis of the sampled data is further described. The results obtained with the RTS method have shown a high level of reliability for the determination of dynamic response. Numéro de notice : A2019-166 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.15292/geodetski-vestnik.2019.01.57-72 date de publication en ligne : 06/01/2019 En ligne : http://dx.doi.org/10.15292/geodetski-vestnik.2019.01.57-72 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92575 [article]

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FFT swept filtering: a bias-free method for processing fringe signals in absolute gravimeters / Petr Křen in Journal of geodesy, vol 93 n° 2 (February 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 2 (February 2019) . - pp 219 - 227 Titre : FFT swept filtering: a bias-free method for processing fringe signals in absolute gravimeters Type de document : Article/Communication Auteurs : Petr Křen, Auteur ; Vojtech Pálinkáš, Auteur ; Pavel Mašika, Auteur ; Miloš Val’ko, Auteur Année de publication : 2019 Article en page(s) : pp 219 - 227 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] distorsion du signal [Termes IGN] erreur systématique [Termes IGN] filtre passe-bande [Termes IGN] gravimètre absolu [Termes IGN] pesanteur terrestre [Termes IGN] régression linéaire [Termes IGN] transformation rapide de Fourier Résumé : (auteur) Absolute gravimeters, based on laser interferometry, are widely used for many applications in geoscience and metrology. Although currently the most accurate FG5 and FG5X gravimeters declare standard uncertainties at the level of 2−3μGal, their inherent systematic errors affect the gravity reference determined by international key comparisons based predominately on the use of FG5-type instruments. The measurement results for FG5-215 and FG5X-251 clearly showed that the measured g-values depend on the size of the fringe signal and that this effect might be approximated by a linear regression with a slope of up to 0.030μGal/mV. However, these empirical results do not enable one to identify the source of the effect or to determine a reasonable reference fringe level for correcting g-values in an absolute sense. Therefore, both gravimeters were equipped with new measuring systems (according to Křen et al. in Metrologia 53:27–40, 2016. https://doi.org/10.1088/0026-1394/53/1/27 applied for FG5), running in parallel with the original systems. The new systems use an analogue-to-digital converter HS5 to digitize the fringe signal and a new method of fringe signal analysis based on FFT swept bandpass filtering. We demonstrate that the source of the fringe size effect is connected to a distortion of the fringe signal due to the electronic components used in the FG5(X) gravimeters. To obtain a bias-free g-value, the FFT swept method should be applied for the determination of zero-crossings. A comparison of g-values obtained from the new and the original systems clearly shows that the original system might be biased by approximately 3−5μGal due to improperly distorted fringe signal processing. Numéro de notice : A2019-079 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1154-y date de publication en ligne : 19/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1154-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92197 [article]

The open data HELI-DEM DTM for the western alpine area: computation and publication / L. Biagi in Applied geomatics, vol 8 n° 3-4 (December 2016)  

Public [article]  inApplied geomatics > vol 8 n° 3-4 (December 2016) . - pp 191 - 200 Titre : The open data HELI-DEM DTM for the western alpine area: computation and publication Type de document : Article/Communication Auteurs : L. Biagi, Auteur ; S. Caldera, Auteur ; L. Carcano, Auteur ; Marco Negretti, Auteur Année de publication : 2016 Article en page(s) : pp 191 - 200 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] Alpes [Termes IGN] données altimétriques [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] European Terrestrial Reference Frame [Termes IGN] fusion de données [Termes IGN] Italie [Termes IGN] modèle numérique de surface [Termes IGN] Suisse [Termes IGN] transformation rapide de Fourier Résumé : (Auteur) Two problems can arise in analyzing Digital Elevation Models (DEMs). Firstly, one interest region could be patched by several partly overlapping models that present similar accuracies and spatial resolutions; they should be merged in one unified model. Moreover, even when the interest region is completely covered by one model, local data with better accuracy could cover partial areas and should be properly merged. All these problems have been addressed within Helvetia-Italy Digital Elevation Model, a project funded by the European Regional Development Fund (ERDF). One specific aim of the project was the creation and the publication of a unified DEM for a part of the Alps between Italy and Switzerland. The interest area is prevalently mountainous, with elevations that range from about 200 to 4600 m. Various elevation datasets were available that were gridded with different spatial resolutions, in different reference frames and coordinates. Moreover, one high resolution LiDAR model was available for some areas. Firstly, a validation was performed that allowed the identification of few blunders and confirmed the general accuracy of the input data. Two DEMs have been produced. Both of them cover the whole project area (boundaries λ = 7.80° East and λ = 10.70° East, φ = 45.10° North and φ = 46.70° North) and are gridded in ETRF2000 geographical coordinates, with a spatial resolution of 2 × 10−4 degrees. The former (named HD-1) has been obtained by interpolating and merging all the low resolution models on a new common grid. HD-1 has been locally corrected by the LiDAR model, where it was available; to avoid sharp discontinuities, the corrections have been filtered by Fast Fourier Transform before applying them. The resulting model has been called HD-2. HD-1 and HD-2 are published by an open access geoservice. Numéro de notice : A2016--054 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1007/s12518-016-0176-5 date de publication en ligne : 26/10/2016 En ligne : http://dx.doi.org/10.1007/s12518-016-0176-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84201 [article]

Comparison among three harmonic analysis techniques on the sphere and the ellipsoid / Hussein Abd-Elmotaal in Journal of applied geodesy, vol 8 n° 1 (April 2014)  

Public [article]  inJournal of applied geodesy > vol 8 n° 1 (April 2014) . - pp 1 - 19 Titre : Comparison among three harmonic analysis techniques on the sphere and the ellipsoid Type de document : Article/Communication Auteurs : Hussein Abd-Elmotaal, Auteur ; Kurt Seitz, Auteur ; Mostafa Abd-Elbaky, Auteur ; Bernhard Heck, Auteur Année de publication : 2014 Article en page(s) : pp 1 - 19 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] anomalie de pesanteur [Termes IGN] Earth Gravity Model 2008 [Termes IGN] ellipsoïde (géodésie) [Termes IGN] harmonique ellipsoïdale [Termes IGN] harmonique sphérique [Termes IGN] méthode des moindres carrés [Termes IGN] transformation rapide de Fourier Résumé : (Auteur) The paper presents a comparison among three different techniques for harmonic analysis on the sphere and the ellipsoid. The EGM2008 global geopotential model has been used up to degree and order 360 in order to create gravity anomaly fields on both the sphere and the ellipsoid as the function fields of the current investigation. Harmonic analysis has then been carried out to compute the dimensionless potential coeficients using the created function fields. Three different harmonic analysis techniques have been applied: the least-squares technique, the Fast Fourier Transform (FFT) technique and the Gauss-Legendre numerical integration technique. The computed coeficients in spherical harmonics have then been compared with EGM2008 (in the frequency domain) and the computed fields on the sphere and the ellipsoid have been compared with fields created by EGM2008 up to degree and order 360 (in the space domain) in order to estimate the accuracy of the three different harmonic analysis techniques used within the current investigation. The results proved that the least-squares technique gives the best accuracy both in frequency and space domain. The FFT technique provides quite good results in a very short cpu time. The Gauss-Legendre technique gives the worst results among the presented techniques, but still the residuals in the space domain are negligibly small. Numéro de notice : A2014-270 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article En ligne : http://www.degruyter.com/view/j/jag.2014.8.issue-1/jag-2013-0008/jag-2013-0008.x [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33173 [article]

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Spectral analysis of structural deformation - A case study / Alojz Kopacik in Journal of applied geodesy, vol 6 n° 3-4 (November 2012)  

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Navigation Signal Processing for GNSS Software Receivers / T. Pany (2010)

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Merging hyperspectral and panchromatic image data: qualitative and quantitative analysis / M. Cetin in International Journal of Remote Sensing IJRS, vol 30 n° 7 (April 2009)

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FFT-enhanced IHS transform method for fusing high-resolution satellite images / Y. Ling in ISPRS Journal of photogrammetry and remote sensing, vol 61 n° 6 (February 2007)

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ERS-2 SAR and IRS-1C LISS III data fusion: a PCA approach to improve remote sensing based geological interpretation / T.J. Majumdar in ISPRS Journal of photogrammetry and remote sensing, vol 61 n° 5 (January 2007)

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Gravimétrie, géoïde et nivellement par GPS en Belgique / Henri Duquenne in XYZ, n° 105 (décembre 2005 - février 2006)

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Digital image processing / Rafael C. Gonzalez (1993)

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Introduction to numerical analysis / J. Stoer (1993)

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Temps-fréquence / Patrick Flandrin (1993)

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FGI studies on satellite gravity gradiometry, 3. 3 Regional high resolution geopotential recovery in geographical coordinates using a Taylor expansion FFT technique / M. Vermeer (1992)

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