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Is waveform worth it? A comparison of LiDAR approaches for vegetation and landscape characterization / Karen Anderson in Remote sensing in ecology and conservation, vol 2 n° 1 (February 2016)
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Titre : Is waveform worth it? A comparison of LiDAR approaches for vegetation and landscape characterization Type de document : Article/Communication Auteurs : Karen Anderson, Auteur ; Steven Hancock, Auteur ; Mathias I. Disney, Auteur ; Kevin J. Gaston, Auteur Année de publication : 2016 Article en page(s) : pp 5 - 15 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] canopée
[Termes IGN] données lidar
[Termes IGN] données localisées 3D
[Termes IGN] forêt
[Termes IGN] forme d'onde
[Termes IGN] sous-bois
[Termes IGN] sous-étageRésumé : (auteur) Light Detection and Ranging (LiDAR) systems are frequently used in ecological studies to measure vegetation canopy structure. Waveform LiDAR systems offer new capabilities for vegetation modelling by measuring the time-varying signal of the laser pulse as it illuminates different elements of the canopy, providing an opportunity to describe the 3D structure of vegetation canopies more fully. This article provides a comparison between waveform airborne laser scanning (ALS) data and discrete return ALS data, using terrestrial laser scanning (TLS) data as an independent validation. With reference to two urban landscape typologies, we demonstrate that discrete return ALS data provided more biased and less consistent measurements of woodland canopy height (in a 100% tree covered plot, height underestimation bias = 0.82 m; SD = 1.78 m) than waveform ALS data (height overestimation bias = 0.65 m; SD = 1.45 m). The same biases were found in suburban data (in a plot consisting of 100% hard targets e.g. roads and pavements), but discrete return ALS were more consistent here than waveform data (SD=0.57 m compared to waveform SD=0.76 m). Discrete return ALS data performed poorly in describing the canopy understorey, compared to waveform data. Our results also highlighted errors in discrete return ALS intensity, which were not present with waveform data. Waveform ALS data therefore offer an improved method for measuring the three-dimensional structure of vegetation systems, but carry a higher data processing cost. New toolkits for analysing waveform data will expedite future analysis and allow ecologists to exploit the information content of waveform LiDAR. Numéro de notice : A2016--166 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.1002/rse2.8 En ligne : http://doi.org/10.1002/rse2.8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=87172
in Remote sensing in ecology and conservation > vol 2 n° 1 (February 2016) . - pp 5 - 15[article]A wavelet-based echo detector for waveform LiDAR data / Cheng-Kai Wang in IEEE Transactions on geoscience and remote sensing, vol 54 n° 2 (February 2016)
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Titre : A wavelet-based echo detector for waveform LiDAR data Type de document : Article/Communication Auteurs : Cheng-Kai Wang, Auteur ; Yi-Hsing Tseng, Auteur ; Chi-Kuei Wang, Auteur Année de publication : 2016 Article en page(s) : pp 757 - 769 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] données lidar
[Termes IGN] forme d'onde
[Termes IGN] modèle numérique de surface
[Termes IGN] onde lidar
[Termes IGN] ondelette
[Termes IGN] semis de points
[Termes IGN] signal laserRésumé : (Auteur) This paper presents a wavelet-based (WB) echo detector that can recover the echoes missed by a light detection and ranging (LiDAR) system via on-the-fly detection. An on-the-fly detection method normally utilizes a simple threshold (TH) to register a target point. Points that belong to weak and/or overlapping echoes are much complicated and are easily missed by TH approaches. The proposed detector based on wavelet transformation is robust to noise and is capable of resolving overlapping echoes. It is thus expected to be good at handling missing echoes. A simulated waveform data set and a real waveform data set of a forest area were both used in this paper. The simulated waveform data were utilized to compare the proposed detector with zero crossing (ZC) and Gaussian decomposition (GD) detectors in terms of their ability to deal with weak or overlapping echoes. The real waveform data set acquired from Leica ALS60 was used to demonstrate a WB algorithm for exploring the missing echoes. Experiments using the simulated data showed that the WB and GD detectors are superior to the ZC detector in finding overlapping echoes. The WB algorithm performs well when dealing with overlapping echoes with a low signal-to-noise ratio. Experiments using the real waveform data show that 31.5% additional weak or overlapping echoes can be detected by the WB detector compared with the point cloud provided by the system. With such additional points, the mean and root-mean-square errors of the digital elevation model differences can be improved from 0.72 and 0.79 m to 0.16 and 0.59 m, respectively. Numéro de notice : A2016-119 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2015.2465148 En ligne : https://doi.org/10.1109/TGRS.2015.2465148 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79999
in IEEE Transactions on geoscience and remote sensing > vol 54 n° 2 (February 2016) . - pp 757 - 769[article]Réservation
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Titre : Advanced modeling and algorithms for high-precision GNSS analysis Type de document : Thèse/HDR Auteurs : Kan Wang, Auteur Editeur : Zurich : Eidgenossische Technische Hochschule ETH - Ecole Polytechnique Fédérale de Zurich EPFZ Année de publication : 2016 Collection : Dissertationen ETH num. 23188 Note générale : bibliographie
thesis submitted to attain the degree of doctor of sciences of ETH ZurichLangues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière
[Termes IGN] antenne GPS
[Termes IGN] centre de phase
[Termes IGN] données BeiDou
[Termes IGN] données Galileo
[Termes IGN] données GPS
[Termes IGN] double différence
[Termes IGN] erreur systématique
[Termes IGN] GPS en mode différentiel
[Termes IGN] horloge
[Termes IGN] phase GNSS
[Termes IGN] positionnement cinématique
[Termes IGN] récepteur GNSS
[Termes IGN] récepteur trifréquence
[Termes IGN] résolution d'ambiguïté
[Termes IGN] retard ionosphèrique
[Termes IGN] Suisse
[Termes IGN] trajet multiple
[Vedettes matières IGN] Traitement de données GNSSRésumé : (auteur) In the recent ten years, the Global Navigation Satellite System (GNSS) processing has experienced a fast development in many areas including the increasing number of frequencies, the higher quality of positioning instruments, e.g. the receiver clocks and the satellite clocks, and more integrated modeling and calculation strategies. This thesis includes investigations of different modeling and parameterization methods in modern GNSS positioning with the focus on three important positioning error sources: the receiver clock errors, the phase ambiguities and the ionospheric delays.
The thesis shows that making use of the high-quality receiver clocks and applying appropriate receiver clock modeling can help to improve the kinematic height estimates, which are highly correlated with the receiver clock parameters. An efficient pre-elimination and back-substitution strategy of epoch parameters with relative clock constraints between subsequent and near-subsequent epochs has been developed to enable processing of, e.g., high-rate data. A detailed analysis of the relationship between the clock quality and the improvement of kinematic heights has been performed. Studies were also conducted to decorrelate the receiver clock parameters, the kinematic heights and the troposphere parameters. Experiments with real data have shown that appropriate deterministic and stochastic clock models can also be helpful to increase the resolution of the estimated Zenith Path Delay (ZPD) parameters without obvious degradation of the stability of the kinematic heights.
The second aspect of the thesis focuses on the resolution of triple-frequency phase ambiguities with different linear combinations. A complete analytical investigation of Geometry-Free (GF) and Ionosphere-Free (IF) triple-frequency phase ambiguity resolution with minimized noise level has been performed for different frequency triplets. The analysis was done separately for the best two linear combinations and the third one. Experiments have shown that the fractional parts and the formal errors of the combined ambiguities of the best two linear combinations are relatively small for Galileo E1, E5b and E5a and GPS L1, L2 and L5 triplets, while the third linear combination remains a challenge. Further analysis with the geostationary satellites of the Beidou Navigation Satellite System (BDS) elaborated in the framework of this thesis has also confirmed that the combined ambiguities from the best two GF and IF linear combinations can be fixed by rounding, while the estimated ambiguities on L1 have relatively large deviations from the values obtained from the traditional dual-frequency double-difference ambiguity resolution. Apart from the triple-frequency ambiguity resolution on the double-difference level, the so-called track-to-track ambiguities between different tracks of the same receiver and the same satellite have also been investigated for the best two triple-frequency linear combinations using GPS L1, L2 and L5 as well as Galileo E1, E5b and E5a observations. The outcome demonstrates that elevation-dependent influences on the observations like Phase Center Variations (PCVs), Phase Center Offsets (PCOs) and multipath are important for the fixing of the track-to-track ambiguities.
The combined track-to-track ambiguities using the best two linear combinations are also effective in detecting problems in the observation data.
The third aspect of the thesis includes the investigation of the differential ionospheric delays and gradients in the region of Switzerland from 1999 to 2013. In differential Global Positioning System (GPS) positioning, the ionospheric delays for short baselines are in most cases small enough to be ignored, except under extreme conditions, e.g., during ionospheric stormy days, and for applications with high integrity requirements, e.g., during approach and landing of aircrafts. This thesis introduces an algorithm using double-difference phase measurements with resolved phase ambiguities and global ionosphere maps provided by the Center for Orbit Determination in Europe (CODE) to extract the single-difference ionospheric delays, and enabling an automatic and robust processing of the data over 15 years. The results show that the daily maximum slant ionospheric gradients calculated from the differential slant ionopheric delays and the baseline lengths from 1999 to 2013 are below the slant ionosphere gradient boundary of the Conterminous United States (CONUS) ionospheric anomaly threat model.Numéro de notice : 17250 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : dissertation : sciences : ETH Zurich : 2016 En ligne : http://dx.doi.org/10.3929/ethz-a-010610972 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81986 Airborne DLSLA 3-D SAR image reconstruction by combination of polar formatting and L_1 regularization / Xueming Peng in IEEE Transactions on geoscience and remote sensing, vol 54 n° 1 (January 2016)
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Titre : Airborne DLSLA 3-D SAR image reconstruction by combination of polar formatting and L_1 regularization Type de document : Article/Communication Auteurs : Xueming Peng, Auteur ; Weixian Tan, Auteur ; Wen Hong, Auteur Année de publication : 2016 Article en page(s) : pp 213 - 226 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications
[Termes IGN] bande P
[Termes IGN] bande X
[Termes IGN] capteur aérien
[Termes IGN] centre de phase
[Termes IGN] image radar moirée
[Termes IGN] polarisation
[Termes IGN] reconstruction d'imageRésumé : (Auteur) Airborne downward-looking sparse linear array 3-D synthetic aperture radar (DLSLA 3-D SAR) operates downward-looking observation and obtains the 3-D microwave scattering information of the observed scene. The cross-track physical sparse linear array is often configured to obtain uniform virtual phase centers in order to adopt the frequency-domain algorithm. However, the virtual phase centers usually have to be nonuniformly and sparsely distributed due to the array elements' installation locations restricted by the airborne platform and the airborne wing tremor effect. In this state, the frequency-domain algorithm cannot be directly used. In this paper, a DLSLA 3-D SAR image reconstruction algorithm that combines polar formatting and L1 regularization is presented. Wave propagation and along-track dimensional imaging are first finished after polar formatting and wavefront curvature phase error compensation; then, cross-track dimensional imaging is completed with the L1 regularization technique. The proposed algorithm is applicable to airborne DLSLA 3-D SAR imaging under nonuniformly and sparsely distributed virtual phase centers condition. The proposed algorithm was verified by 3-D distributed scene simulation experiment (P-band circular SAR image was selected as radar cross-section input, and X-band digital elevation model of the same area was selected as the coordinate positions of the scene) and the field experiment. Image reconstruction results and image reconstruction performances, such as normalized radar cross section, height errors, and orthographic projection image grayscale distribution, are demonstrated and analyzed with different signal-to-noise ratios, different array sparsity, and the incomplete compensated residual oscillation error 3-D distributed scene simulation experiments. Simulation and field experimental results show the good performance in focusing and the robustness of the proposed algorithm. Numéro de notice : A2016-077 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2015.2453202 En ligne : https://doi.org/10.1109/TGRS.2015.2453202 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79846
in IEEE Transactions on geoscience and remote sensing > vol 54 n° 1 (January 2016) . - pp 213 - 226[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 065-2016011 SL Revue Centre de documentation Revues en salle Disponible Apport de la télédétection radar satellitaire pour la cartographie de la forêt des Landes / Yousra Hamrouni (2016)
Titre : Apport de la télédétection radar satellitaire pour la cartographie de la forêt des Landes Type de document : Mémoire Auteurs : Yousra Hamrouni, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2016 Autre Editeur : Champs/Marne : Université Paris-Est Marne-la-Vallée UPEM Importance : 60 p. Format : 21 x 30 cm Note générale : Bibliographie
Master 2ème année, domaine Science, Technologie, Santé, mention Géomatique, spécialité Information Géographique, Analyse Spatiale et TélédétectionLangues : Français (fre) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications
[Termes IGN] analyse texturale
[Termes IGN] bande C
[Termes IGN] bande L
[Termes IGN] bande X
[Termes IGN] carte de la végétation
[Termes IGN] carte forestière
[Termes IGN] classification par forêts d'arbres décisionnels
[Termes IGN] forêt
[Termes IGN] image ALOS-PALSAR
[Termes IGN] image radar moirée
[Termes IGN] image Sentinel-SAR
[Termes IGN] image TerraSAR-X
[Termes IGN] Landes (40)
[Termes IGN] paramètre de Haralick
[Termes IGN] télédétection en hyperfréquenceIndex. décimale : IGAST Mémoires du Master Information Géographique, Analyse Spatiale et Télédétection Résumé : (auteur) Avoir un suivi en temps réel des forêts est crucial pour évaluer leur réponse face aux évènements environnementaux. Ce suivi est devenu possible ces dernières années à travers des données de télédétection satellitaires ou aéroportées. C'est dans ce contexte que s'inscrit ce stage qui vise à déterminer rapport de la télédétection radar satellitaire pour la cartographie de la forêt des Landes. Des données en bande X, C et L pour les respectivement les capteurs TerraSAR-X, Sentinel-1A et PALSAR-2 ont été mises à disposition afin d'explorer le potentiel des différentes bandes et les résolutions spatiale. Le potentiel de l'analyse texturale a été évalué en calculant les indicateurs de texture d'Haralick sur les données de très haute résolution spatiale (TerraSAR-X) et les coefficients de variation sur les données de haute résolution spatiale (Sentinel-1A et PALSAR-2). Deux approches méthodologiques ont été investiguées : i) une première approche consiste à travailler à la très haute résolution spatiale en calculant les indicateurs de texture d'Haralick sur les données TerraSAR-X et les coefficients de variation sur les données Sentinel-1A et PALSAR-2 et ii) une deuxième approche a été de travailler à l'échelle spatiale de Sentinel-1A et PALSAR-2.
La performance des deux méthodes a été évaluée à travers les résultats de classification Random Forest. Les résultats montrent que l'analyse de texture est sensible aux hétérogénéités intra parcellaires et permet de caractériser les parcelles à une échelle très fine qui nécessite des données de validation à cette même échelle. La série temporelle Sentinel-1A a donné les résultats les plus performants et la combinaison des trois capteurs a amélioré les résultats de classification, surtout pour la bande C et X.Note de contenu : Introduction
1 - Etat de l'art sur l'application de l'analyse de texture en télédétection
2 - Bases théoriques
3 - Matériels et méthodes
4 - Résultats
ConclusionNuméro de notice : 21552 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Mémoire masters divers Organisme de stage : MATIS (IGN) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90511 Réservation
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