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Auteur J. Wu |
Documents disponibles écrits par cet auteur (6)
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Monitoring ground subsidence in Shanghai maglev area using two kinds of SAR data / J. Wu in Journal of applied geodesy, vol 6 n° 3-4 (November 2012)
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Titre : Monitoring ground subsidence in Shanghai maglev area using two kinds of SAR data Type de document : Article/Communication Auteurs : J. Wu, Auteur ; L. Zhang, Auteur ; et al., Auteur Année de publication : 2012 Article en page(s) : pp 209 - 213 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications
[Termes IGN] effondrement de terrain
[Termes IGN] image ALOS-PALSAR
[Termes IGN] image Envisat-ASAR
[Termes IGN] image radar moirée
[Termes IGN] interféromètrie par radar à antenne synthétique
[Termes IGN] réseau métropolitain
[Termes IGN] Shanghai (Chine)
[Termes IGN] subsidence
[Termes IGN] surveillance d'ouvrageRésumé : (Auteur) Shanghai maglev is a very fast traffic tool, so it is very strict with the stability of the roadbed. However, the ground subsidence is a problem in Shanghai because of the poor geological condition and human-induced factors. So it is necessary to monitor ground subsidence in the area along the Shanghai maglev precisely and frequently. Traditionally, a precise levelling method is used to survey along the track. It is expensive and time consuming, and can only get the ground subsidence information on sparse benchmarks. Recently, the small baseline differential SAR technique plays a valuable part in monitoring ground subsidence, which can extract ground subsidence information with high spatial resolution in a wide area. In this paper, L-band ALOS PALSAR data and C-band Envisat ASAR data are used to extract ground subsidence information using the SBAS method in the Shanghai maglev area. The results show that the general pattern of ground subsidence from InSAR processing of two differential bands of SAR images is similar. Both results show that there is no significant ground subsidence on the maglev line. Near the railway line, there are a few places with subsidence rates at about -20 mm/y or even more, such as Chuansha town, the junction of the maglev and Waihuan road. Numéro de notice : A2012-599 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1515/jag-2012-0024 En ligne : http://www.degruyter.com/view/j/jag.2012.6.issue-3-4/jag-2012-0024/jag-2012-0024 [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32045
in Journal of applied geodesy > vol 6 n° 3-4 (November 2012) . - pp 209 - 213[article]A robust signal preprocessing chain for small-footprint waveform LiDAR / J. Wu in IEEE Transactions on geoscience and remote sensing, vol 50 n° 8 (August 2012)
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Titre : A robust signal preprocessing chain for small-footprint waveform LiDAR Type de document : Article/Communication Auteurs : J. Wu, Auteur ; Jan Van Aardt, Auteur ; J. Mcglinchy, Auteur ; Gregory P. Asner, Auteur Année de publication : 2012 Article en page(s) : pp 3242 - 3255 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] Afrique du sud (état)
[Termes IGN] biomasse
[Termes IGN] données lidar
[Termes IGN] données localisées 3D
[Termes IGN] étalonnage
[Termes IGN] forme d'onde
[Termes IGN] lasergrammétrie
[Termes IGN] prétraitement du signal
[Termes IGN] savane
[Termes IGN] signal lidarRésumé : (Auteur) The extraction of structural object metrics from a next-generation remote sensing modality, namely waveform Light Detection and Ranging (LiDAR), has garnered increasing interest from the remote sensing research community. However, the raw incoming (received) LiDAR waveform typically exhibits a stretched, misaligned, and relatively distorted character. In other words, the LiDAR signal is smeared and the effective temporal (vertical) resolution decreases, which is attributed to a fixed time span allocated for detection, the sensor's variable outgoing pulse signal, off-nadir scanning, the receiver impulse response impacts, and system noise. Theoretically, such a loss of resolution and increased data ambiguity can be remediated by using proven signal preprocessing approaches. In this paper, we present a robust signal preprocessing chain for waveform LiDAR calibration, which includes noise reduction, deconvolution, waveform registration, and angular rectification. This preprocessing chain was initially validated using simulated waveform data, which were derived via the digital imaging and remote sensing image generation modeling environment. We also verified the approach using real small-footprint waveform LiDAR data collected by the Carnegie Airborne Observatory in a savanna region of South Africa and specifically in terms of modeling woody biomass in this region. Metrics, including the spectral angle for cross-section recovery assessment and goodness-of-fit (R2) statistics, along with the root-mean-squared error for woody biomass estimation, were used to provide a comprehensive quantitative evaluation of the performance of this preprocessing chain. Results showed that our approach significantly increased our ability to recover the temporal signal resolution, improved geometric rectification of raw waveform LiDAR, and resulted in improved waveform-based woody biomass estimation. This preprocessing chain has the potential to be applied across the board for h- gh fidelity processing of small-footprint waveform LiDAR data, thereby facilitating the extraction of valid and useful structural metrics from ground objects. Numéro de notice : A2012-389 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2011.2178420 Date de publication en ligne : 04/01/2012 En ligne : https://doi.org/10.1109/TGRS.2011.2178420 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31835
in IEEE Transactions on geoscience and remote sensing > vol 50 n° 8 (August 2012) . - pp 3242 - 3255[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 065-2012081 RAB Revue Centre de documentation En réserve L003 Disponible Cell-based automatic deformation computation by analyzing terrestrial Lidar point clouds / J. Wu in Photogrammetric Engineering & Remote Sensing, PERS, vol 78 n° 4 (April 2012)
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Titre : Cell-based automatic deformation computation by analyzing terrestrial Lidar point clouds Type de document : Article/Communication Auteurs : J. Wu, Auteur ; P.Y. Gilliéron, Auteur ; Bertrand Merminod, Auteur Année de publication : 2012 Article en page(s) : pp 317 - 329 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] données lidar
[Termes IGN] données localisées 3D
[Termes IGN] érosion
[Termes IGN] lasergrammétrie
[Termes IGN] modèle de déformation tectonique
[Termes IGN] semis de pointsRésumé : (Auteur) This paper presents a cell-based approach for computing the deformation of a monitored object by analyzing point cloud data from terrestrial lidar. This approach can automatically generate an informative deformation description (called “deformation map”) with distinctive deformation characteristics for different partial areas. The approach consists of three major computing steps: (a) “split” - the space of the monitored object is divided into 3D uniform cells, (b) “detect” - deformation parameters for each cell (called “meta-deformation”) are estimated by comparing the point clouds in the cell sampled at Epochs I and II, and (c) “merge” - the adjacent cells with similar meta-deformation are combined together in a partial area with a consistent “sub-deformation.” The main contributions of this paper are: (a) a hybrid deformation model for incremental and comprehensive deformation representation, including metadeformation, sub-deformation and deformation map, (b) a systematic procedure of “split-detect-merge” to automatically and gradually estimate the hybrid deformation model, and (c) a complete validation with a couple of synthetic and real datasets. Numéro de notice : A2012-177 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.78.4.317 En ligne : https://doi.org/10.14358/PERS.78.4.317 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31624
in Photogrammetric Engineering & Remote Sensing, PERS > vol 78 n° 4 (April 2012) . - pp 317 - 329[article]A comparison of illumination geometry-based methods for topographic correction of QuickBird images of an undulant area / J. Wu in ISPRS Journal of photogrammetry and remote sensing, vol 63 n° 2 (March - April 2008)
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Titre : A comparison of illumination geometry-based methods for topographic correction of QuickBird images of an undulant area Type de document : Article/Communication Auteurs : J. Wu, Auteur ; M. Bauer, Auteur ; D. Wang, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 223 - 236 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] analyse comparative
[Termes IGN] correction d'image
[Termes IGN] détail topographique
[Termes IGN] éclairement lumineux
[Termes IGN] exitance spectrale
[Termes IGN] image Quickbird
[Termes IGN] modèle numérique de surfaceRésumé : (Auteur) The high spatial resolution of QuickBird satellite images makes it possible to show spatial variability at fine details. However, the effect of topography-induced illumination variations become more evident, even in moderately sloped areas. Based on a high resolution (1 m) digital elevation model generated with high-frequency real-time kinematic global position system measurements, this study assessed topographic effects on QuickBird images of an undulant area (with a maximum slope of 7.4°) under different illumination and ground conditions. For land surfaces that were characterized by a non-Lambertian reflection, significant bidirectional variations in spectral radiances were found in all bands. The effectiveness of four illumination geometry-based topographic correction methods was evaluated. The results indicated that the empirical correction was the most effective method for all spectral bands in both solar and view directions, while the cosine correction gave the worst results. The C correction (in the solar direction) and the Minnaert correction reduced topographic effects, but not as effectively as the empirical correction. For the Lambertian, topographic effects were substantial only in the near infrared band in the solar direction. Bidirectional variations of spectral radiances in other bands and/or view directions were minimal and topographic corrections may not be necessary. None of these methods significantly changed the spatial variability of spectral radiances, although the histogram distributions were greatly modified by the cosine correction and the Minnaert correction. Copyright ISPRS Numéro de notice : A2008-116 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2007.08.004 En ligne : https://doi.org/10.1016/j.isprsjprs.2007.08.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29111
in ISPRS Journal of photogrammetry and remote sensing > vol 63 n° 2 (March - April 2008) . - pp 223 - 236[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 081-08021 SL Revue Centre de documentation Revues en salle Disponible Real-time speed limit sign recognition based on locally adaptive thresholding and depth-first-search / J. Wu in Photogrammetric Engineering & Remote Sensing, PERS, vol 71 n° 4 (April 2005)
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Titre : Real-time speed limit sign recognition based on locally adaptive thresholding and depth-first-search Type de document : Article/Communication Auteurs : J. Wu, Auteur ; Y.J. Tsai, Auteur Année de publication : 2005 Article en page(s) : pp 405 - 414 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] acquisition de données
[Termes IGN] image vidéo
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] reconnaissance de caractères
[Termes IGN] réseau routier
[Termes IGN] segmentation d'image
[Termes IGN] seuillage d'image
[Termes IGN] signalisation routière
[Termes IGN] temps réel
[Termes IGN] Visual C++
[Termes IGN] zone d'intérêtRésumé : (Auteur) Stop signs and speed limit signs (SLS) are the most popular and significant traffic signs on roadways. Unlike extracting stop signs with a distinct red color, extracting SLS in a realtime environment is much more challenging. This paper presents an algorithm for recognizing SLS from video imaging and extracting the numerical numbers of SLS to support real-time road inventory data collection operations. The algorithm consists of color segmentation based on locally adaptive thresholding extraction of regions of interest (ROI) using a depth-first-search algorithm, followed by speed limit sign detection and speed limit number extraction by means of optical character recognition and 2D correlation. The algorithm was implemented in Visual C++ language and tested on a non-Hyper-Threading Pentium IV PC with 3.06GHZ CPU using the images taken in the field with different image sizes. The average processing time for an image of 1200 X 800 pixels is about 125 ms. Experimental results from 1,401 video images show 0 percent false positives out of 1,278 images containing no SLS, and 3 percent false negatives out of 123 images containing SLS. Numéro de notice : A2005-159 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.71.4.405 En ligne : https://doi.org/10.14358/PERS.71.4.405 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27297
in Photogrammetric Engineering & Remote Sensing, PERS > vol 71 n° 4 (April 2005) . - pp 405 - 414[article]Wavelet triangulated irregular networks / J. Wu in International journal of geographical information science IJGIS, vol 17 n° 3 (may 2003)
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