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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 descripteurs IGN] distorsion du signal [Termes descripteurs IGN] erreur systématique [Termes descripteurs IGN] filtre passe-bande [Termes descripteurs IGN] gravimètre absolu [Termes descripteurs IGN] pesanteur terrestre [Termes descripteurs IGN] régression linéaire [Termes descripteurs 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 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]

Filter design for GOCE gravity gradients / Zs. Polgár Polgár in Geocarto international, vol 28 n° 1-2 (February - May 2013)  

Public [article]  inGeocarto international > vol 28 n° 1-2 (February - May 2013) . - pp 28 - 45 Titre : Filter design for GOCE gravity gradients Type de document : Article/Communication Auteurs : Zs. Polgár Polgár, Auteur ; L. Sujbertb, Auteur ; L. Földváry, Auteur ; P. Asbóth, Auteur ; J. Ádám, Auteur Année de publication : 2013 Article en page(s) : pp 28 - 45 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] données GOCE [Termes descripteurs IGN] filtrage du rayonnement [Termes descripteurs IGN] filtre passe-bande [Termes descripteurs IGN] gradient de gravitation [Termes descripteurs IGN] levé gravimétrique Résumé : (Auteur) The GOCE satellite observes gravity gradients with unprecedented accuracy and resolution. The GOCE observations are reliable within a well-defined measurement bandwidth. In this study, different finite and infinite impulse response filters have been designed to obtain the demanded pass. Exhaustive time and frequency domain investigations prove that the proposed infinite impulse response filter can be a real competitor of the existing solution of the filtering problem. Numéro de notice : A2013-275 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106049.2012.687401 date de publication en ligne : 24/05/2012 En ligne : https://doi.org/10.1080/10106049.2012.687401 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32413 [article]

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Interference suppression algorithm for SAR based on time-frequency transform / S. Zhang in IEEE Transactions on geoscience and remote sensing, vol 49 n° 10 Tome 1 (October 2011)

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 49 n° 10 Tome 1 (October 2011) . - pp 3765 - 3779 Titre : Interference suppression algorithm for SAR based on time-frequency transform Type de document : Article/Communication Auteurs : S. Zhang, Auteur ; X. Xing, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 3765 - 3779 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes descripteurs IGN] filtre passe-bande [Termes descripteurs IGN] image radar moirée [Termes descripteurs IGN] interférence [Termes descripteurs IGN] transformation de Fourier [Termes descripteurs IGN] transformation en ondelettes Résumé : (Auteur) The goal of this paper is to suppress the narrowband interference (NBI) and wideband interference (WBI) in synthetic aperture radar (SAR) by using a nonparametric method. The method is based on the analysis of time-frequency characteristic of NBI and WBI from which an interference suppression filter combined with the constant false alarm rate algorithm is designed. In this approach, the short-time Fourier transform (STFT) is used to estimate the instantaneous frequency of the SAR echo data with interference. In the STFT domain, the instantaneous frequency spectrum is represented by wavelet, and then, the designed filter filters the corresponding wavelet coefficients of the interference components. In addition, this algorithm is robust to time-varying NBI and WBI. The performance of the proposed approach is evaluated by the simulated and measured data, and the effectiveness is demonstrated. Numéro de notice : A2011-428 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31207 [article]

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An empirical investigation of cross-sensor relationships of NDVI and red/near-infrared reflectance using EO-1 Hyperion data / T. Miura in Remote sensing of environment, vol 100 n° 2 (30 January 2006)

Public [article]  inRemote sensing of environment > vol 100 n° 2 (30 January 2006) . - pp 223 - 236 Titre : An empirical investigation of cross-sensor relationships of NDVI and red/near-infrared reflectance using EO-1 Hyperion data Type de document : Article/Communication Auteurs : T. Miura, Auteur ; A. Huete, Auteur ; H. Yoshioka, Auteur Année de publication : 2006 Article en page(s) : pp 223 - 236 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes descripteurs IGN] analyse comparative [Termes descripteurs IGN] bande rouge [Termes descripteurs IGN] Brésil [Termes descripteurs IGN] étalonnage des données [Termes descripteurs IGN] filtre passe-bande [Termes descripteurs IGN] flore locale [Termes descripteurs IGN] forêt tropicale [Termes descripteurs IGN] image EO1-Hyperion [Termes descripteurs IGN] image hyperspectrale [Termes descripteurs IGN] image Landsat-ETM+ [Termes descripteurs IGN] image Terra-MODIS [Termes descripteurs IGN] Normalized Difference Vegetation Index [Termes descripteurs IGN] rayonnement proche infrarouge [Termes descripteurs IGN] réflectance spectrale [Termes descripteurs IGN] savane Résumé : (Auteur) Long term observations of global vegetation from multiple satellites require much effort to ensure continuity and compatibility due to differences in sensor characteristics and product generation algorithms. In this study, we focused on the band-pass filter differences and empirically investigated cross-sensor relationships of the normalized difference vegetation index (NDVI) and reflectance. The specific objectives were: 1) to understand the systematic trends in cross-sensor relationships of the NDVI and reflectance as a function of spectral band-passes, 2) to examine/ identify the relative importance of the spectral features (i.e., the green peak, red edge, and leaf liquid water absorption regions) in and the mechanism(s) of causing the observed systematic trends, and 3) to evaluate the performance of several empirical cross-calibration methods in modelling the observed systematic trends. A Level 1A Hyperion hyperspectral image acquired over a tropical forest-savanna transitional region in Brazil was processed to simulate atmospherically corrected reflectances and NDVI for various band-passes, including Terra Moderate Resolution Imaging Spectro-radiometer (MODIS), NOAA-14 Advanced Very High Resolution Radiometer (AVHRR), and Landsat7 Enhanced Thematic Mapper Plus (ETM+). Data were extracted from various land cover types typically found in tropical forest and savanna biomes and used for analyses. Both NDVI and reflectance relationships among the sensors were neither linear nor unique and were found to exhibit complex patterns and band-pass dependencies. The reflectance relationships showed strong land cover dependencies. The NDVI relationships, in contrast, did not show land cover dependencies, but resulted in non-linear forms. From sensitivity analyses, the green peak (550 nm) and red-NIR transitional (680780 nm) features were identified as the key factors in producing the observed land cover dependencies and non-linearity in cross-sensor relationships. In particular, differences in the extents to which the red and/or NIR band-passes included these features significantly influenced the forms and degrees of non-linearity in the relationships. Translation of MODIS NDVI to "AVHRR Iike" NDVI using a weighted average of MODIS green and red bands performed very poorly, resulting in no reduction of overall discrepancy between MODIS and AVHRR NDVI. Cross-calibration of NDVI and reflectance using NDVI-based quadratic functions performed well, reducing their differences to +.025 units for the NDVI and +.01 units for the reflectances; however, many of the translation results suffered from bias errors. The present results suggest that distinct translation equations and coefficients need to be developed for every sensor pairs and that land cover-dependency need to be explicitly accounted for to reduce bias errors. Numéro de notice : A2006-034 Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27761 [article]

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Microstrip filters for RF/microwave applications / J.S. Hong (2001)

Public Titre : Microstrip filters for RF/microwave applications Type de document : Monographie Auteurs : J.S. Hong, Auteur ; M.J. Lancaster, Auteur Editeur : New York, Londres, Hoboken (New Jersey), ... : John Wiley & Sons Année de publication : 2001 Collection : Wiley Series in Microwave and Optical Engineering Importance : 471 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-0-471-38877-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes descripteurs IGN] filtre [Termes descripteurs IGN] filtre passe-bande [Termes descripteurs IGN] hyperfréquence [Termes descripteurs IGN] rayonnement radioélectrique Résumé : (Editeur) Microstrip Filters for RF/Microwave Applications is the only professional reference focusing solely on microstrip filters. It offers a unique and comprehensive treatment of filters bases on the microstrip structure and includes full design methodologies that are also applicable to waveguide and other transmission line filters. The authors include coverage of new configurations with advanced filtering characteristics, new design techniques, and methods for filter miniaturization. The book utilizes numerous design examples to illustrate and emphasize computer analysis and synthesis while also discussing the applications of commercially available software. Other highlights include : - Lowpass and bandpass filters - Highpass abd bandstop filters - Full-wave electromagnetic simulation - Advanced materials and technologies - Coupled resonator circuits - Computer-aided design for low-cost/higt-volume production - Compact filters and filter minaturization. Numéro de notice : 11725 Thématique : IMAGERIE/POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54480

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Modex / Stéphane Mallat (1998)

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