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Use of HRSC-A for sampling bidirectional reflectance / Antero Kukko in ISPRS Journal of photogrammetry and remote sensing, vol 59 n° 6 (November 2005)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 59 n° 6 (November 2005) . - pp 323 - 341 Titre : Use of HRSC-A for sampling bidirectional reflectance Type de document : Article/Communication Auteurs : Antero Kukko, Auteur ; Risto Kuittinen, Auteur ; Juha Hyyppä, Auteur Année de publication : 2005 Article en page(s) : pp 323 - 341 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] anisotropie [Termes IGN] distribution du coefficient de réflexion bidirectionnelle BRDF [Termes IGN] échantillon [Termes IGN] GPS-INS [Termes IGN] image aérienne [Termes IGN] modèle numérique de surface [Termes IGN] qualité des données Résumé : (Auteur) This paper describes a method for sampling bidirectional reflectance information from multiangular airborne images. The method uses high resolution surface models to determinate the location of the imaged point on the ground and the orientation of the measured surface fragment. Since natural surfaces scatter incident radiation anisotropically, viewing and illumination conditions play a critical role in the interpretation of remotely sensed images. Thus, directionally defined reflectance data are needed for the modelling and correction of bidirectional effects on airborne optical images. Two test sites were imaged with a wide range of viewing azimuth angles at two different times. A high resolution HRSC-A stereo camera was used for image acquisition. Algorithms were implemented to reconstruct the image acquisition and retrieve the image samples from the HRSC-A image data. Combined with GPS and INS data, automatically derived high resolution digital surface models, including vegetation canopies, houses, etc., were used to determine the viewing and illumination geometry on the target surface. The brightness of a sample point was recorded as a measure for reflectance. A large number of directionally defined samples and a wide angular range of sample geometry were obtained. The images were first classified. Sampled reflectance data were verified by investigating the bidirectional reflectance of five agricultural and forest targets. Errors affecting the data quality, such as angular uncertainty, were studied. The multiangular image data, the developed sampling methods and the obtained bidirectional dataset proved to be applicable in investigations of bidirectional reflectance effects of natural targets. Airborne imagery combined with high resolution digital surface models permit extensive investigation of the bidirectional reflectance of a wide range of natural objects and large habitats. Copyright ISPRS Numéro de notice : A2005-489 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2005.06.001 En ligne : https://doi.org/10.1016/j.isprsjprs.2005.06.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27625 [article]

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Estimating forest biomass using small footprint LiDAR data: An individual tree-based approach that incorporates training data / Z.J. Bortolot in ISPRS Journal of photogrammetry and remote sensing, vol 59 n° 6 (November 2005)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 59 n° 6 (November 2005) . - pp 342 - 360 Titre : Estimating forest biomass using small footprint LiDAR data: An individual tree-based approach that incorporates training data Type de document : Article/Communication Auteurs : Z.J. Bortolot, Auteur ; R. Wynne, Auteur Année de publication : 2005 Article en page(s) : pp 342 - 360 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] couvert forestier [Termes IGN] données de terrain [Termes IGN] données lidar [Termes IGN] forêt tempérée [Termes IGN] houppier [Termes IGN] lasergrammétrie [Termes IGN] masse végétale [Termes IGN] optimisation (mathématiques) [Termes IGN] Pinus taeda [Termes IGN] régression [Termes IGN] sylviculture [Termes IGN] Virginie (Etats-Unis) Résumé : (Auteur) A new individual tree-based algorithm for determining forest biomass using small footprint LiDAR data was developed and tested. This algorithm combines computer vision and optimization techniques to become the first training data-based algorithm specifically designed for processing forest LiDAR data. The computer vision portion of the algorithm uses generic properties of trees in small footprint LiDAR canopy height models (CHMs) to locate trees and find their crown boundaries and heights. The ways in which these generic properties are used for a specific scene and image type is dependent on 11 parameters, nine of which are set using training data and the Nelder-Mead simplex optimization procedure. Training data consist of small sections of the LiDAR data and corresponding ground data. After training, the biomass present in areas without ground measurements is determined by developing a regression equation between properties derived from the LiDAR data of the training stands and biomass, and then applying the equation to the new areas. A first test of this technique was performed using 25 plots (radius = 15 m) in a loblolly pine plantation in central Virginia, USA (37.42N, 78.68W) that was not intensively managed, together with corresponding data from a LiDAR canopy height model (resolution = 0.5 m). Results show correlations (r) between actual and predicted aboveground biomass ranging between 0.59 and 0.82, and RMSEs between 13.6 and 140.4 t/ha depending on the selection of training and testing plots, and the minimum diameter at breast height (7 or 10 cm) of trees included in the biomass estimate. Correlations between LiDAR-derived plot density estimates were low (0.22 Numéro de notice : A2005-490 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2005.07.001 En ligne : https://doi.org/10.1016/j.isprsjprs.2005.07.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27626 [article]

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Effects of laser beam alignment tolerance on lidar accuracy / D. Latypov in ISPRS Journal of photogrammetry and remote sensing, vol 59 n° 6 (November 2005)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 59 n° 6 (November 2005) . - pp 361 - 368 Titre : Effects of laser beam alignment tolerance on lidar accuracy Type de document : Article/Communication Auteurs : D. Latypov, Auteur Année de publication : 2005 Article en page(s) : pp 361 - 368 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] données lidar [Termes IGN] erreur systématique [Termes IGN] étalonnage géométrique [Termes IGN] faisceau [Termes IGN] Lidar [Termes IGN] orientation du capteur [Termes IGN] plan de vol [Termes IGN] point d'appui [Termes IGN] télémétrie laser aéroporté Résumé : (Auteur) One of the major lidar error sources not yet analysed in the literature is the tolerance of the laser beam alignment with respect to the scanning mirror. In this paper, the problem of quantifying these errors is solved for rotating polygon mirror type lidar systems. An arbitrary deviation of the beam from its design direction -the vector of beam misalignment- can be described by two independent parameters. We choose these as horizontal and vertical components of the misalignment vector in the body frame. Either component affects both, horizontal and vertical lidar accuracy. Horizontal lidar errors appear as scan line distortions-along and across track shifts, rotations and scaling. It is shown that the horizontal component of misalignment results in a scan line first being shifted across the track and then rotated around the vertical at the new center of the scan line. Resulting vertical lidar error, being a linear function of the scan angle, is similar to that produced by a roll bias. The vertical component of the beam misalignment causes scan line scaling and an along track shift. The corresponding vertical error is quadratic with respect to the scan angle. The magnitude of these effects is significant even at tight alignment tolerances and cannot be realistically accounted for in the conventional calibration model, which includes only range, attitude and GPS biases. Therefore, in order to attain better accuracy, this model must be expanded to include the beam misalignment parameters as well. Addition of new parameters into the model raises a question of whether they can be reliably solved for. To give a positive answer to this question, a calibration method must utilize not only ground control information, which is typically very limited, but also the relative accuracy information from the overlapping flight lines. Copyright ISPRS Numéro de notice : A2005-491 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2005.09.002 En ligne : https://doi.org/10.1016/j.isprsjprs.2005.09.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27627 [article]

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Stratified sampling of satellite images with a systematic grid of points / F.J. Gallego in ISPRS Journal of photogrammetry and remote sensing, vol 59 n° 6 (November 2005)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 59 n° 6 (November 2005) . - pp 369 - 376 Titre : Stratified sampling of satellite images with a systematic grid of points Type de document : Article/Communication Auteurs : F.J. Gallego, Auteur Année de publication : 2005 Article en page(s) : pp 369 - 376 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] distribution spatiale [Termes IGN] échantillonnage d'image [Termes IGN] erreur systématique [Termes IGN] grille régulière [Termes IGN] image Landsat-ETM+ [Termes IGN] mosaïque d'images [Termes IGN] polygone de Thiessen Résumé : (Auteur) Sampling satellite images presents some specific characteristics : images overlap and many of them fall partially outside the studied region. A careless sampling may introduce an important bias. This paper illustrates the risk of bias and the efficiency improvements of systematic, pps (probability proportional to size) and stratified sampling. A sampling method is proposed with the following criteria: (a) unbiased estimators are easy to compute; (b) it can be combined with stratification; (c) within each stratum, sampling probability is proportional to the area of the sampling unit; and (d) the geographic distribution of the sample is reasonably homogeneous. Thiessen polygons computed on image centres are sampled through a systematic grid of points. The sampling rates in different strata are tuned by dividing the systematic grid into subgrids or replicates and taking for each stratum a certain number of replicates. The approach is illustrated with an application to the estimation of the geometric accuracy of Image2000, a Landsat ETM+ mosaic of the European Union. Copyright ISPRS Numéro de notice : A2005-492 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2005.10.001 En ligne : https://doi.org/10.1016/j.isprsjprs.2005.10.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27628 [article]

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