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Least-squares cross-wavelet analysis and its applications in geophysical time series / Ebrahim Ghaderpour in Journal of geodesy, vol 92 n° 10 (October 2018)
[article]
Titre : Least-squares cross-wavelet analysis and its applications in geophysical time series Type de document : Article/Communication Auteurs : Ebrahim Ghaderpour, Auteur ; Elmas Sinem Ince, Auteur ; Spiros D. Pagiatakis, Auteur Année de publication : 2018 Article en page(s) : pp 1223 - 1236 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données GOCE
[Termes IGN] données ITGB
[Termes IGN] gradient de gravitation
[Termes IGN] matrice de covariance
[Termes IGN] méthode des moindres carrés
[Termes IGN] série temporelle
[Termes IGN] transformation en ondelettesRésumé : (Auteur) The least-squares wavelet analysis, an alternative to the classical wavelet analysis, was introduced in order to analyze unequally spaced and non-stationary time series exhibiting components with variable amplitude and frequency over time. There are a few methods such as cross-wavelet transform and wavelet coherence that can analyze two time series together. However, these methods cannot generally be used to analyze unequally spaced and non-stationary time series with associated covariance matrices that may have trends and/or datum shifts. A new method of analyzing two time series together, namely the least-squares cross-wavelet analysis, is developed and applied to study the disturbances in the gravitational gradients observed by GOCE satellite that arise from plasma flow in the ionosphere represented by Poynting flux. The proposed method also shows its outstanding performance on the Westford–Wettzell very long baseline interferometry baseline length and temperature series. Numéro de notice : A2018-462 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1156-9 Date de publication en ligne : 26/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1156-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91061
in Journal of geodesy > vol 92 n° 10 (October 2018) . - pp 1223 - 1236[article]Digital aerial photogrammetry for assessing cumulative spruce budworm defoliation and enhancing forest inventories at a landscape-level / Tristan R.H. Goodbody in ISPRS Journal of photogrammetry and remote sensing, vol 142 (August 2018)
[article]
Titre : Digital aerial photogrammetry for assessing cumulative spruce budworm defoliation and enhancing forest inventories at a landscape-level Type de document : Article/Communication Auteurs : Tristan R.H. Goodbody, Auteur ; Nicholas C. Coops, Auteur ; Txomin Hermosilla, Auteur ; Piotr Tompalski, Auteur ; Grant MacCartney, Auteur ; David A. MacLean, Auteur Année de publication : 2018 Article en page(s) : pp 1 - 11 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] défoliation
[Termes IGN] dégradation de la flore
[Termes IGN] échantillonnage d'image
[Termes IGN] insecte nuisible
[Termes IGN] inventaire forestier (techniques et méthodes)
[Termes IGN] méthode des moindres carrés
[Termes IGN] Ontario (Canada)
[Termes IGN] photogrammétrie aérienne
[Termes IGN] photogrammétrie numérique
[Termes IGN] Picea abies
[Termes IGN] régression linéaire
[Termes IGN] semis de points
[Termes IGN] surface terrière
[Termes IGN] surveillance forestière
[Vedettes matières IGN] Inventaire forestierRésumé : (Auteur) Spruce budworm (Choristoneura fumiferana [Clem.], Lepidoptera: Tortricidae) is a native defoliating insect with an important disturbance role in the eastern boreal forests of North America. With an extensive history of outbreaks and associated impacts on forest structural changes and timber supply, the mapping of spruce budworm defoliation has been of major management importance. In this study we assessed the ability of high spatial resolution digital aerial photogrammetric (DAP) data to predict cumulative defoliation as well as basal area and merchantable volume in spruce budworm host stands in the Gordon Cosens Forest south of Kapuskasing, Ontario, Canada. To do so, DAP derived structural and spectral metrics were incorporated to implement a stratified sampling design to improve the efficiency and cost-effectiveness of field surveying. Standard forest inventory measurements including diameter and height, as well as ocular and branch level defoliation assessments were undertaken on thirty 400 m2 radius plots. A partial least squares analysis was performed to determine whether structural metrics from a DAP point cloud could be influenced by spruce budworm defoliation, as well as determine the relative effectiveness of spectral (e.g. mean NDVI) vs. structural (e.g. 90th percentile of height) metrics, or their combination, for predicting cumulative defoliation. Results indicated that spectral metrics were the most effective for predicting cumulative defoliation (R2 = 0.79), while structural metrics were the least effective (R2 = 0.49). Metrics characterizing variance of the spectral values were found to be the most important predictors. Structural metrics and linear regression were also used to estimate landscape-level volume and basal area per hectare yielding R2 = 0.80 and R2 = 0.90, respectively. Outcomes of this analysis indicate that DAP-derived spectral metrics were more capable of modeling cumulative defoliation, while structural metrics were effective for landscape-level estimations of standard forest inventory attributes. This analysis indicated that the provision of both spectral and structural metrics from a single aerial imagery survey has potential to enhance defoliation monitoring and forest attribute modeling at a landscape-level. Numéro de notice : A2018-290 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2018.05.012 Date de publication en ligne : 01/08/2018 En ligne : https://doi.org/10.1016/j.isprsjprs.2018.05.012 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90408
in ISPRS Journal of photogrammetry and remote sensing > vol 142 (August 2018) . - pp 1 - 11[article]Réservation
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[article]
Titre : Differential positioning based on the orthogonal transformation algorithm with GNSS multi-system Type de document : Article/Communication Auteurs : Xiao Liang, Auteur ; Zhigang Huang, Auteur ; Honglei Qin, Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière
[Termes IGN] erreur instrumentale
[Termes IGN] erreur systématique
[Termes IGN] filtre de Kalman
[Termes IGN] méthode des moindres carrés
[Termes IGN] positionnement différentiel
[Termes IGN] résolution d'ambiguïté
[Termes IGN] simple différence
[Vedettes matières IGN] Traitement de données GNSSRésumé : (Auteur) Combining global navigation satellite systems (GNSSs) will significantly increase the number of visible satellites and, thus, will improve the geometry of observed satellites, resulting in improved positioning reliability and accuracy. We focus on GNSS multi-system differential positioning based on a single-system orthogonal transformation algorithm. The orthogonal transformation algorithm using single-difference measurements is proposed to avoid the high correlation between measurements and the unnecessary prominence to the reference satellite in double-difference positioning. In addition, the algorithm uses a more straightforward recursive least squares method to avoid the effect of uncertainties of the Kalman filter. We discuss the model differences between combined system positioning and single-system positioning and verify that the combining observations of different systems should start to be used after clock biases have been reduced, respectively. Moreover, as to rising and setting of satellites in multi-system differential positioning, we propose to use matrix transform to separate the setting satellites of combined systems at an epoch. This can avoid the correlation of initial integer ambiguity vectors of different systems. The experimental results show that the proposed method can handle the change of satellites automatically and combine multiple systems for reliable and accuracy differential positioning. The method especially outperforms the basic single-system orthogonal transformation positioning and traditional multi-system double-difference positioning in a complex environment. Numéro de notice : A2018-371 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-018-0754-6 Date de publication en ligne : 02/07/2018 En ligne : https://doi.org/10.1007/s10291-018-0754-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90763
in GPS solutions > vol 22 n° 3 (July 2018)[article]A methodology for least-squares local quasi-geoid modelling using a noisy satellite-only gravity field model / R. Klees in Journal of geodesy, vol 92 n° 4 (April 2018)
[article]
Titre : A methodology for least-squares local quasi-geoid modelling using a noisy satellite-only gravity field model Type de document : Article/Communication Auteurs : R. Klees, Auteur ; D.C. Slobbe, Auteur ; Hassan Hashemi Farahani, Auteur Année de publication : 2018 Article en page(s) : pp 431 - 442 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] fonction de base radiale
[Termes IGN] matrice de covariance
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle de géopotentiel
[Termes IGN] quasi-géoïde
[Termes IGN] résiduRésumé : (Auteur) The paper is about a methodology to combine a noisy satellite-only global gravity field model (GGM) with other noisy datasets to estimate a local quasi-geoid model using weighted least-squares techniques. In this way, we attempt to improve the quality of the estimated quasi-geoid model and to complement it with a full noise covariance matrix for quality control and further data processing. The methodology goes beyond the classical remove–compute–restore approach, which does not account for the noise in the satellite-only GGM. We suggest and analyse three different approaches of data combination. Two of them are based on a local single-scale spherical radial basis function (SRBF) model of the disturbing potential, and one is based on a two-scale SRBF model. Using numerical experiments, we show that a single-scale SRBF model does not fully exploit the information in the satellite-only GGM. We explain this by a lack of flexibility of a single-scale SRBF model to deal with datasets of significantly different bandwidths. The two-scale SRBF model performs well in this respect, provided that the model coefficients representing the two scales are estimated separately. The corresponding methodology is developed in this paper. Using the statistics of the least-squares residuals and the statistics of the errors in the estimated two-scale quasi-geoid model, we demonstrate that the developed methodology provides a two-scale quasi-geoid model, which exploits the information in all datasets. Numéro de notice : A2018-063 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1076-0 Date de publication en ligne : 06/11/2017 En ligne : https://doi.org/10.1007/s00190-017-1076-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89399
in Journal of geodesy > vol 92 n° 4 (April 2018) . - pp 431 - 442[article]Regional geoid computation by least squares modified Hotine’s formula with additive corrections / Silja Märdla in Journal of geodesy, vol 92 n° 3 (March 2018)
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Titre : Regional geoid computation by least squares modified Hotine’s formula with additive corrections Type de document : Article/Communication Auteurs : Silja Märdla, Auteur ; Artu Ellmann, Auteur ; Jonas Ågren, Auteur ; Lard Erik Sjöberg, Auteur Année de publication : 2018 Article en page(s) : pp 253 - 270 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] anomalie de pesanteur
[Termes IGN] formule de Stokes
[Termes IGN] géoïde local
[Termes IGN] méthode des moindres carrés
[Termes IGN] quasi-géoïdeRésumé : (Auteur) Geoid and quasigeoid modelling from gravity anomalies by the method of least squares modification of Stokes’s formula with additive corrections is adapted for the usage with gravity disturbances and Hotine’s formula. The biased, unbiased and optimum versions of least squares modification are considered. Equations are presented for the four additive corrections that account for the combined (direct plus indirect) effect of downward continuation (DWC), topographic, atmospheric and ellipsoidal corrections in geoid or quasigeoid modelling. The geoid or quasigeoid modelling scheme by the least squares modified Hotine formula is numerically verified, analysed and compared to the Stokes counterpart in a heterogeneous study area. The resulting geoid models and the additive corrections computed both for use with Stokes’s or Hotine’s formula differ most in high topography areas. Over the study area (reaching almost 2 km in altitude), the approximate geoid models (before the additive corrections) differ by 7 mm on average with a 3 mm standard deviation (SD) and a maximum of 1.3 cm. The additive corrections, out of which only the DWC correction has a numerically significant difference, improve the agreement between respective geoid or quasigeoid models to an average difference of 5 mm with a 1 mm SD and a maximum of 8 mm. Numéro de notice : A2018-060 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1061-7 Date de publication en ligne : 11/09/2017 En ligne : https://doi.org/10.1007/s00190-017-1061-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89393
in Journal of geodesy > vol 92 n° 3 (March 2018) . - pp 253 - 270[article]An accurate Kriging-based regional ionospheric model using combined GPS/BeiDou observations / Mohamed Abdelazeem in Journal of applied geodesy, vol 12 n° 1 (January 2018)PermalinkMixed integer–real least squares estimation for precise GNSS positioning using a modified ambiguity function approach / Krzysztof Nowel in GPS solutions, vol 22 n° 1 (January 2018)PermalinkPerformance analysis of BDS/GPS precise point positioning with undifferenced ambiguity resolution / Min Wang in Advances in space research, vol 60 n° 12 (15 December 2017)PermalinkEfficient weighted total least-squares solution for partial errors-in-variables model / J. Zhao in Survey review, vol 49 n° 356 (November 2017)PermalinkWeighted coordinate transformation formulated by standard least-squares theory / D. Mihajlovic in Survey review, vol 49 n° 356 (November 2017)PermalinkMulti-dimensional and multi-temporal motion estimation of a beam surface during dynamic testing using low-frame rate digital cameras / I. Detchev in Applied geomatics, vol 9 n° 3 (September 2017)PermalinkA robust weighted total least-squares solution with Lagrange multipliers / X. Gong in Survey review, vol 49 n° 354 (September 2017)PermalinkAnalyse numérique / Mustapha Lakrib (2017)PermalinkPermalinkEléments de géodésie et de la théorie des moindres carrés / Abdelmajid Ben Hadj Salem (2017)Permalink