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A method to determine secondary codes and carrier phases of short snapshot signals / Xiao Liu in Navigation : journal of the Institute of navigation, vol 69 n° 4 (Fall 2022)
[article]
Titre : A method to determine secondary codes and carrier phases of short snapshot signals Type de document : Article/Communication Auteurs : Xiao Liu, Auteur ; Pau Closas, Auteur ; Adria Gusi-Amigó, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 541 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] ambiguïté entière
[Termes IGN] phase
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] signal GNSS
[Termes IGN] temps instantanéRésumé : (auteur) Recently, the Snapshot Real-Time Kinematic (SRTK) technique was demonstrated, which aims at achieving high accuracy navigation solutions with a very short signal collection. The main challenge in implementing SRTK is the generation of valid carrier-phase measurements, which relies on a data bit ambiguity (DBA) resolution process. For pilot signals, this step is equivalent to the correct selection of secondary code indexes (SCIs) from the ambiguous sets obtained from a multi-hypotheses (MH) acquisition process. Currently, SCI ambiguities are solved independently for each satellite. However, this method is ineffective when the snapshot signal is relatively short. In order to tackle this problem, this article proposes a new method that makes use of assistance data and processes information from all satellites to jointly solve the DBA issue. This new method is shown to be more effective in determining the correct SCI and enabling valid snapshot carrier-phase measurements, largely expanding the scope of high-accuracy snapshot positioning. Numéro de notice : A2022-868 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.541 Date de publication en ligne : 21/04/2022 En ligne : https://doi.org/10.33012/navi.541 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102161
in Navigation : journal of the Institute of navigation > vol 69 n° 4 (Fall 2022) . - n° 541[article]Multi-frequency simulation of ionospheric scintillation using a phase-screen model / Fernando D. Nunes in Navigation : journal of the Institute of navigation, vol 69 n° 4 (Fall 2022)
[article]
Titre : Multi-frequency simulation of ionospheric scintillation using a phase-screen model Type de document : Article/Communication Auteurs : Fernando D. Nunes, Auteur ; Fernando M.G. Sousa, Auteur ; José M.V. Marçal, Auteur Année de publication : 2022 Article en page(s) : n° 545 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] amplitude
[Termes IGN] correction ionosphérique
[Termes IGN] fréquence multiple
[Termes IGN] ionosphère
[Termes IGN] méthode de Monte-Carlo
[Termes IGN] phase
[Termes IGN] scintillation
[Termes IGN] série temporelle
[Termes IGN] signal GNSS
[Termes IGN] teneur totale en électronsRésumé : (auteur) A fast Monte Carlo technique to simulate equatorial ionospheric scintillation on global navigation satellite system signals is proposed. The algorithm uses a single-layer phase-screen model of the ionosphere and the scintillation is expressed as a Huygens-Fresnel integral (HFI). By assuming a specially-tailored random phase screen, the HFI can be expressed in closed form as a combination of Fresnel integrals. We statistically characterize the amplitude and phase computed by the HFI for different values of the scintillation index S4. Results for the L1, L2, and L5 bands were obtained and compared with real data, showing good agreement. Some of the advantages of the proposed technique are: (a) the amplitude and phase of the scintillation process are simultaneously obtained; (b) arbitrarily long ionospheric scintillation time series with pre-defined stationary characteristics are synthesized; and (c) several scintillation time series corresponding to different carrier frequencies are generated using a common phase-screen model. Numéro de notice : A2022-918 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.545 Date de publication en ligne : 18/06/2022 En ligne : https://doi.org/10.33012/navi.545 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102446
in Navigation : journal of the Institute of navigation > vol 69 n° 4 (Fall 2022) . - n° 545[article]Development and long-term dynamics of old-growth beech-fir forests in the Pyrenees: Evidence from dendroecology and dynamic vegetation modelling / Dario Martín-Benito in Forest ecology and management, vol 524 (November-15 2022)
[article]
Titre : Development and long-term dynamics of old-growth beech-fir forests in the Pyrenees: Evidence from dendroecology and dynamic vegetation modelling Type de document : Article/Communication Auteurs : Dario Martín-Benito, Auteur ; Juan Alberto Molina-Valero, Auteur ; César Pérez-Cruzado, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 120541 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Abies alba
[Termes IGN] analyse diachronique
[Termes IGN] biomasse forestière
[Termes IGN] dendroécologie
[Termes IGN] dynamique de la végétation
[Termes IGN] Espagne
[Termes IGN] exploitation forestière
[Termes IGN] Fagus sylvatica
[Termes IGN] forêt ancienne
[Termes IGN] forêt tempérée
[Termes IGN] modèle de croissance végétale
[Termes IGN] ombre
[Termes IGN] perturbation écologique
[Termes IGN] Pyrénées (montagne)
[Vedettes matières IGN] ForesterieRésumé : (auteur) Ecological knowledge on long-term forest dynamics and development has been primarily derived from the study of old-growth forests. Centuries of forest management have decreased the extent of temperate old-growth forests in Europe and altered managed forests. Disentangling the effects of past human disturbances and climate on current species composition is crucial for understanding the long-term development of forests under global change. In this study, we investigated disturbance and recruitment dynamics in two forests in the Western Pyrenees (Spain) with contrasting management history: an old-growth forest and a long-untouched forest, both dominated by the two shade-tolerant species Fagus sylvatica (European beech) and Abies alba (Silver fir). We used dendroecological methods in seven plots to analyse forest structure, growth patterns and disturbance histories in these forests. We benchmarked these data with the dynamic vegetation model ForClim to examine the effects of natural and human-induced disturbances on forest development, structure and species composition. Disturbance regimes differed between the study forests, but none showed evidence of stand replacing disturbances, either natural or human induced. Low disturbance rates and continuous recruitment of beech and fir dominated the old-growth forest over the last 400 years. In contrast, the long-untouched forest was intensively disturbed in 1700–1780, probably by logging, with lower natural disturbance rates thereafter. Beech and fir recruitment preferentially occurred after more intense disturbances, despite the high shade tolerance of both beech and fir. Higher fir abundance in the long-untouched forest than in the old-growth forest appeared to be related to its human-induced disturbances. ForClim closely simulated forest potential natural vegetation with a dominance of beech over fir, but overestimated the presence of less shade-tolerant species. Previously observed local fir decline may result from natural forest successional processes after logging. Within ∼200 years after logging cessation, some long-untouched forest structural attributes converged towards old-growth forest, but legacy effects still affected species composition and structure. Natural disturbance regimes in beech-fir forests of the Western Pyrenees induce temporal fluctuations between beech and fir abundance, with a natural tendency for beech dominance in advanced developmental stages with low disturbance rates. Numéro de notice : A2022-732 Affiliation des auteurs : non IGN Thématique : FORET/MATHEMATIQUE Nature : Article DOI : 10.1016/j.foreco.2022.120541 Date de publication en ligne : 23/09/2022 En ligne : https://doi.org/10.1016/j.foreco.2022.120541 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101695
in Forest ecology and management > vol 524 (November-15 2022) . - n° 120541[article]An advanced bidirectional reflectance factor (BRF) spectral approach for estimating flavonoid content in leaves of Ginkgo plantations / Kai Zhou in ISPRS Journal of photogrammetry and remote sensing, vol 193 (November 2022)
[article]
Titre : An advanced bidirectional reflectance factor (BRF) spectral approach for estimating flavonoid content in leaves of Ginkgo plantations Type de document : Article/Communication Auteurs : Kai Zhou, Auteur ; Lin Cao, Auteur ; Shiyun Yin, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : pp 1 - 16 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] bande spectrale
[Termes IGN] coefficient de corrélation
[Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF
[Termes IGN] feuille (végétation)
[Termes IGN] Ginkgo biloba
[Termes IGN] image à haute résolution
[Termes IGN] indice foliaire
[Termes IGN] Kiangsou (Chine)
[Termes IGN] réflectance végétaleRésumé : (auteur) As a key phenolic pigment concentrated in the surface tissues of leaves, flavonoids (Flav) are the major bioactive ingredients in Ginkgo leaf extracts. Flav are also marked natural antioxidants and significant indicators of biotic and abiotic stresses, critical for determining cultivation quality and enhancing Flav yield. In particular, area-based Flav (Flavarea) is related to the shortwave-blue light interaction within leaves per unit leaf area, whereas mass-based Flav (Flavmass) is useful for the quantitative assessment of Flav yield. In order to accurately estimate the contents of Flavarea and Flavmass in leaves of Ginkgo plantations, in this study, we developed an advanced bidirectional reflectance factor (BRF) spectra-based approach by reducing the effects of specular reflection and enhancing the absorption signals of Flav (in the shortwave-blue region of spectrum), using a suite of new spectral indices (SIs) (i.e., flavonoid index (FI), modified flavonoid index (mFI) and double difference index (DD)) calculated from the leaf clip equipped spectrometers-collected data. The results demonstrated that most of the SIs derived from the developed BRF spectra-based approach obtained relatively high performance for Flav estimation by alleviating adverse effects of specular reflection to different extents (CV-R2 = 0.60–0.76). In specific, DDnir434,421 selected from DD-type indices performed (CV-R2 = 0.76 for Flavarea; CV-R2 = 0.69 for Flavmass) better than other indices. These findings represent marked potentials of the developed BRF spectra-based approach for non-destructively estimating leaf Flav content, as well as improving the understanding of the mechanisms of specular effects on Flav estimations in leaves of Ginkgo plantations. Numéro de notice : A2022-744 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2022.08.020 Date de publication en ligne : 09/09/2022 En ligne : https://doi.org/10.1016/j.isprsjprs.2022.08.020 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101727
in ISPRS Journal of photogrammetry and remote sensing > vol 193 (November 2022) . - pp 1 - 16[article]A new partial ambiguity resolution method based on modified solution separation and GNSS epoch-differencing / Yang Jiang in Journal of geodesy, vol 96 n° 11 (November 2022)
[article]
Titre : A new partial ambiguity resolution method based on modified solution separation and GNSS epoch-differencing Type de document : Article/Communication Auteurs : Yang Jiang, Auteur ; Wei Ding, Auteur ; Yuting Gao, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 88 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] compensation Lambda
[Termes IGN] erreur de positionnement
[Termes IGN] phase
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] récepteur GNSS
[Termes IGN] résolution d'ambiguïtéRésumé : (auteur) Partial ambiguity resolution has been widely used in real-time kinematic (RTK) positioning to provide accurate and continuous centimeter-level positioning solutions. Current PAR methods are concerned with the exclusion of ambiguities that otherwise would result in low rate of full ambiguity resolution (FAR). With an assumption of unbiased ambiguities, the traditional PAR methods use the ambiguity-domain test statistics and probability-domain quantitative evaluation to select and validate the ambiguity subset. Consequentially, they would degrade the performance using low-cost devices in challenging environments where ambiguity biases exist, causing high probabilities of false alarm and missed detection of PAR and subsequently poor availability and accuracy of PAR. To deal with this issue, in this study, we propose a new PAR method for application in challenging environments. The proposed method consists of two major steps. First, a global navigation satellite system epoch-differencing (GED) algorithm is applied to derive a prior ambiguity solution. Second, we use a modified solution separation (SS) method with the prior ambiguity solution as an external input to obtain more accurate ambiguity test statistics. Based on a dynamic road test under environments with significant signal blockages, the performance of the proposed method is analyzed by using a low-cost GNSS receiver. The proposed method provides ambiguity test statistics with higher accuracy and can achieve 73.19% and 50.55% improvement in the accuracy and availability of the fixed solution, compared with the traditional PAR methods. Besides, the RMS of positioning errors with fixed solution are 1.03 cm, 0.70 cm, and 1.50 cm for the proposed PAR method in the east, north, and upward directions, respectively, which are 1.06 cm, 0.72 cm, and 1.35 cm for SS-based PAR, and 5.29 cm, 0.86 cm, and 5.56 cm for ILS-based PAR. The proposed PAR method achieves 90.36% fixed epochs, versus 79.06%, and 88.28%, for ILS-based PAR and SS-based PAR, respectively. Numéro de notice : A2022-810 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01674-1 Date de publication en ligne : 02/11/2022 En ligne : https://doi.org/10.1007/s00190-022-01674-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101967
in Journal of geodesy > vol 96 n° 11 (November 2022) . - n° 88[article]On the relation of GNSS phase center offsets and the terrestrial reference frame scale: a semi-analytical analysis / Oliver Montenbruck in Journal of geodesy, vol 96 n° 11 (November 2022)PermalinkTerrain representation using orientation / Gene Trantham in Cartography and Geographic Information Science, vol 49 n° 6 (November 2022)PermalinkAn efficient method to compensate receiver clock jumps in real-time precise point positioning / Shaoguang Xu in Remote sensing, vol 14 n° 20 (October-2 2022)PermalinkCaractériser l’environnement compétitif des arbres : dépassons la surface terrière ! / Thomas Cordonnier in Revue forestière française, vol 73 n° 6 (2021)PermalinkChallenging the link between functional and spectral diversity with radiative transfer modeling and data / Javier Pacheco-Labradora in Remote sensing of environment, vol 280 (October 2022)PermalinkEstimation of ionospheric total electron content using GNSS observations derived from a smartphone / Li Xu in GPS solutions, vol 26 n° 4 (October 2022)PermalinkEstimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites / Yanli Zheng in Remote sensing, vol 14 n° 18 (September-2 2022)PermalinkThe FIRST model: Spatiotemporal fusion incorrporting spectral autocorrelation / Shuaijun Liu in Remote sensing of environment, vol 279 (September-15 2022)PermalinkDetection of potential gold mineralization areas using MF-fuzzy approach on multispectral data / Tohid Nouri in Geocarto international, Vol 37 n° 17 ([20/08/2022])PermalinkComparison of PBIA and GEOBIA classification methods in classifying turbidity in reservoirs / Douglas Stefanello Facco in Geocarto international, vol 37 n° 16 ([15/08/2022])PermalinkComparative analysis of real-time precise point positioning method in terms of positioning and zenith tropospheric delay estimation / Omer Faruk Atiz in Survey review, vol 55 n° 388 (January 2023)PermalinkFull-waveform classification and segmentation-based signal detection of single-wavelength bathymetric LiDAR / Xue Ji in IEEE Transactions on geoscience and remote sensing, vol 60 n° 8 (August 2022)PermalinkIncorporation of digital elevation model, normalized difference vegetation index, and Landsat-8 data for land use land cover mapping / Jwan Al-Doski in Photogrammetric Engineering & Remote Sensing, PERS, vol 88 n° 8 (August 2022)PermalinkMapping land-use intensity of grasslands in Germany with machine learning and Sentinel-2 time series / Maximilian Lange in Remote sensing of environment, vol 277 (August 2022)PermalinkAn accurate train positioning method using tightly-coupled GPS + BDS PPP/IMU strategy / Wei Jiang in GPS solutions, vol 26 n° 3 (July 2022)PermalinkEvaluation of QZSS orbit and clock products for real-time positioning applications / Brian Bramanto in Journal of applied geodesy, vol 16 n° 3 (July 2022)PermalinkMulti-frequency phase-only PPP-RTK model applied to BeiDou data / Pengyu Hou in GPS solutions, vol 26 n° 3 (July 2022)PermalinkOutliers and uncertainties in GNSS ZTD estimates from double-difference processing and precise point positioning / Katarzyna Stępniak in GPS solutions, vol 26 n° 3 (July 2022)PermalinkSimulation-driven 3D forest growth forecasting based on airborne topographic LiDAR data and shading / Štefan Kohek in International journal of applied Earth observation and geoinformation, vol 111 (July 2022)PermalinkDART-Lux: An unbiased and rapid Monte Carlo radiative transfer method for simulating remote sensing images / Yingjie Wang in Remote sensing of environment, vol 274 (June 2022)Permalink