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Compression strategies for LiDAR waveform cube / Grzegorz Jóźków in ISPRS Journal of photogrammetry and remote sensing, vol 99 (January 2015)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 99 (January 2015) . - pp 1 - 13 Titre : Compression strategies for LiDAR waveform cube Type de document : Article/Communication Auteurs : Grzegorz Jóźków, Auteur ; Charles K. Toth, Auteur ; Mihaela Quirk, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 1 - 13 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] compression de données [Termes IGN] données lidar [Termes IGN] forme d'onde pleine Résumé : (Auteur) Full-waveform LiDAR data (FWD) provide a wealth of information about the shape and materials of the surveyed areas. Unlike discrete data that retains only a few strong returns, FWD generally keeps the whole signal, at all times, regardless of the signal intensity. Hence, FWD will have an increasingly well-deserved role in mapping and beyond, in the much desired classification in the raw data format. Full-waveform systems currently perform only the recording of the waveform data at the acquisition stage; the return extraction is mostly deferred to post-processing. Although the full waveform preserves most of the details of the real data, it presents a serious practical challenge for a wide use: much larger datasets compared to those from the classical discrete return systems. Atop the need for more storage space, the acquisition speed of the FWD may also limit the pulse rate on most systems that cannot store data fast enough, and thus, reduces the perceived system performance. This work introduces a waveform cube model to compress waveforms in selected subsets of the cube, aimed at achieving decreased storage while maintaining the maximum pulse rate of FWD systems. In our experiments, the waveform cube is compressed using classical methods for 2D imagery that are further tested to assess the feasibility of the proposed solution. The spatial distribution of airborne waveform data is irregular; however, the manner of the FWD acquisition allows the organization of the waveforms in a regular 3D structure similar to familiar multi-component imagery, as those of hyper-spectral cubes or 3D volumetric tomography scans. This study presents the performance analysis of several lossy compression methods applied to the LiDAR waveform cube, including JPEG-1, JPEG-2000, and PCA-based techniques. Wide ranges of tests performed on real airborne datasets have demonstrated the benefits of the JPEG-2000 Standard where high compression rates incur fairly small data degradation. In addition, the JPEG-2000 Standard-compliant compression implementation can be fast and, thus, used in real-time systems, as compressed data sequences can be formed progressively during the waveform data collection. We conclude from our experiments that 2D image compression strategies are feasible and efficient approaches, thus they might be applied during the acquisition of the FWD sensors. Numéro de notice : A2014-633 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2014.10.003 En ligne : https://doi.org/10.1016/j.isprsjprs.2014.10.003 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75059 [article]

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081-2015011	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Seeing through shadow: Modelling surface irradiance for topographic correction of Landsat ETM+ data / Tobias Schulmann in ISPRS Journal of photogrammetry and remote sensing, vol 99 (January 2015)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 99 (January 2015) . - pp 14 - 24 Titre : Seeing through shadow: Modelling surface irradiance for topographic correction of Landsat ETM+ data Type de document : Article/Communication Auteurs : Tobias Schulmann, Auteur ; Marwan Katurji, Auteur ; Peyman Zawar-Reza, Auteur Année de publication : 2015 Article en page(s) : pp 14 - 24 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] aérosol [Termes IGN] albedo [Termes IGN] correction des ombres [Termes IGN] montagne [Termes IGN] Nouvelle-Zélande [Termes IGN] pente [Termes IGN] réflectance de surface [Termes IGN] transfert radiatif Résumé : (Auteur) Despite advances in remote sensing, retrieving surface properties at high resolutions in complex terrain is a major challenge. Slope and aspect as well as the topography surrounding a target impact surface insolation and lead to variability in calculated surface reflectance even for homogeneous land cover. Retrieval of surface reflectance is particularly problematic in case of topographic shading, where the total irradiation at the surface is a combination of diffuse irradiation and terrain-reflected irradiation from nearby slopes. To facilitate the retrieval of surface reflectance from high-resolution optical remote sensing, we have explored the feasibility of using a three dimensional radiative transfer code to simulate gridded surface irradiance for a View the MathML source∼37km2 area in the New Zealand Southern Alps. We have tested the sensitivity of simulated irradiance and calculated surface reflectance both in- and outside shaded areas to atmospheric aerosol content, surface albedo, atmospheric boundary layer structure and different solar spectra. Retrieved surface reflectance has been shown to be highly sensitive to atmospheric aerosols and surface albedo, particularly for areas shaded by topography. Not considering atmospheric aerosols in topographic correction can increase derived surface reflectance by well over 50%, while terrain-reflected irradiance can contribute 40% to surface reflectance in shaded areas, even for wider valleys. Both factors should therefore be considered in topographic correction of satellite imagery, even for relatively aerosol-free atmospheres and low surface albedo. Topographic correction for the whole scene was performed with the model settings resulting in the smallest RMSD between surface reflectivity in shaded and unshaded areas of similar land cover. Topographic correction based on 3D radiative transfer simulations has proven to effectively remove topographic effects and almost equalise derived mean reflectance in- and outside shaded areas. While the effective removal of shadows likely requires a higher dynamic range than Landsat’s ETM+ can offer, we suggest further evaluation of this approach in future studies at other sites and with other sensors. Numéro de notice : A2014-634 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2014.10.004 En ligne : https://doi.org/10.1016/j.isprsjprs.2014.10.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75060 [article]

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081-2015011	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Hierarchical extraction of urban objects from mobile laser scanning data / Bisheng Yang in ISPRS Journal of photogrammetry and remote sensing, vol 99 (January 2015)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 99 (January 2015) . - pp 45 - 57 Titre : Hierarchical extraction of urban objects from mobile laser scanning data Type de document : Article/Communication Auteurs : Bisheng Yang, Auteur ; Zhen Dong, Auteur ; Gang Zhao, Auteur ; Wenxia Dai, Auteur Année de publication : 2015 Article en page(s) : pp 45 - 57 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] détection d'objet [Termes IGN] extraction automatique [Termes IGN] levé urbain [Termes IGN] semis de points [Termes IGN] Station laser ultra-mobile [Termes IGN] traitement de données [Termes IGN] voxel Résumé : (Auteur) Point clouds collected in urban scenes contain a huge number of points (e.g., billions), numerous objects with significant size variability, complex and incomplete structures, and variable point densities, raising great challenges for the automated extraction of urban objects in the field of photogrammetry, computer vision, and robotics. This paper addresses these challenges by proposing an automated method to extract urban objects robustly and efficiently. The proposed method generates multi-scale supervoxels from 3D point clouds using the point attributes (e.g., colors, intensities) and spatial distances between points, and then segments the supervoxels rather than individual points by combining graph based segmentation with multiple cues (e.g., principal direction, colors) of the supervoxels. The proposed method defines a set of rules for merging segments into meaningful units according to types of urban objects and forms the semantic knowledge of urban objects for the classification of objects. Finally, the proposed method extracts and classifies urban objects in a hierarchical order ranked by the saliency of the segments. Experiments show that the proposed method is efficient and robust for extracting buildings, streetlamps, trees, telegraph poles, traffic signs, cars, and enclosures from mobile laser scanning (MLS) point clouds, with an overall accuracy of 92.3%. Numéro de notice : A2014-635 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2014.10.005 En ligne : https://doi.org/10.1016/j.isprsjprs.2014.10.005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75061 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
081-2015011	RAB	Revue	Centre de documentation	En réserve L003	Disponible

A rigorous cylinder-based self-calibration approach for terrestrial laser scanners / Ting On Chan in ISPRS Journal of photogrammetry and remote sensing, vol 99 (January 2015)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 99 (January 2015) . - pp 84 - 99 Titre : A rigorous cylinder-based self-calibration approach for terrestrial laser scanners Type de document : Article/Communication Auteurs : Ting On Chan, Auteur ; Derek D. Lichti, Auteur ; David Belton, Auteur Année de publication : 2015 Article en page(s) : pp 84 - 99 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] étalonnage d'instrument [Termes IGN] étalonnage géométrique [Termes IGN] lasergrammétrie [Termes IGN] télémètre laser terrestre Résumé : (Auteur) Existing self-calibration methods for terrestrial laser scanners are predominantly point-based and plane-based. In this paper, we present a new cylinder-based self-calibration method with its variants for several scanners having different architectures and scanning mechanisms. The method not only increases the flexibility of in situ self-calibration, but also its rigor because of reduced functional dependencies between adjustment parameters. Based on the analysis of linear dependencies between columns of the design matrices for both the cylindrical and planar models, it is shown that using the vertical cylindrical model is advantageous over using the planar model as some high linear dependencies can be avoided. The proposed method and its variants were first applied to two simulated datasets, to compare their effectiveness, and then to three real datasets captured by three different types of scanners are presented: a Faro Focus 3D (a phase-based panoramic scanner); a Velodyne HDL-32E (a pulse-based multi spinning beam scanner); and a Leica ScanStation C10 (a dual operating-mode scanner). The experimental results show that the proposed method can properly estimate the additional parameters with high precision. More importantly, no high correlations were found between the additional parameters and other parameters when the network configuration is strong. The overall results indicate that the proposed calibration method is rigorous and flexible. Numéro de notice : A2014-636 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2014.11.003 En ligne : https://doi.org/10.1016/j.isprsjprs.2014.11.003 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75062 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
081-2015011	RAB	Revue	Centre de documentation	En réserve L003	Disponible