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Small-footprint lidar estimation of sub-canopy elevation and tree height in a tropical rain forest landscape / M.L. Clarke in Remote sensing of environment, vol 91 n° 1 (15/05/2004)
[article]
Titre : Small-footprint lidar estimation of sub-canopy elevation and tree height in a tropical rain forest landscape Type de document : Article/Communication Auteurs : M.L. Clarke, Auteur ; D. Clark, Auteur ; D.A. Roberts, Auteur Année de publication : 2004 Article en page(s) : pp 68 - 89 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] corrélation linéaire
[Termes IGN] données lidar
[Termes IGN] erreur moyenne quadratique
[Termes IGN] forêt tropicale
[Termes IGN] interpolation inversement proportionnelle à la distance
[Termes IGN] modèle numérique de surface
[Termes IGN] modèle numérique de terrain
[Termes IGN] sous-bois
[Termes IGN] télémétrie laser aéroportéRésumé : (Auteur) Meso-scale digital terrain models (DTMs) and canopy-height estimates, or digital canopy models (DCMs), are two lidar products that have immense potential for research in tropical rain forest (TRF) ecology and management. In this study, we used a small-footprint lidar sensor (airborne laser scanner, ALS) to estimate sub-canopy elevation and canopy height in an evergreen tropical rain forest. A fully automated, local-minima algorithm was developed to separate lidar ground returns from overlying vegetation returns. We then assessed inverse distance weighted (IDW) and ordinary kriging (OK) geostatistical techniques for the interpolation of a sub-canopy DTM. OK was determined to be a superior interpolation scheme because it smoothed fine-scale variance created by spurious understory heights in the ground-point dataset. The final DTM had a linear correlation of 1.00 and a root-mean-square error (RMSE) of 2.29 m when compared against 3859 well-distributed ground-survey points. In old-growth forests, RMS error on steep slopes was 0.67 m greater than on flat slopes. On flatter slopes, variation in vegetation complexity associated with land use caused highly significant differences in DTM error distribution across the landscape. The highest DTM accuracy observed in this study was 0.58-m RMSE, under flat, open-canopy areas with relatively smooth surfaces. Lidar ground retrieval was complicated by dense, multi-layered evergreen canopy in old-growth forests, causing DTM overestimation that increased RMS error to 1.95 m.
A DCM was calculated from the original lidar surface and the interpolated DTM. Individual and plot-scale heights were estimated from DCM metrics and compared to field data measured using similar spatial supports and metrics. For old-growth forest emergent trees and isolated pasture trees greater than 20 in tall, individual tree heights were underestimated and had 3.67- and 2.33-m mean absolute error (MAE), respectively. Linear-regression models explained 51% (4.15-m RMSE) and 95% (2.41-m RMSE) of the variance, respectively. It was determined that improved elevation and field-height estimation in pastures explained why individual pasture trees could be estimated more accurately than old-growth trees. Mean height of tree stems in 32 young agroforestry plantation plots (0.38 to 18.53 m tall) was estimated with a mean absolute error of 0.90 m (r 2 = 0,97; 1.08-m model RMSE) using the mean of lidar returns in the plot. As in other small-footprint lidar studies, plot mean height was underestimated; however, our plot-scale results have stronger linear models for tropical, leaf-on hardwood trees than has been previously reported for temperate-zone conifer and deciduous hardwoods.Numéro de notice : A2004-237 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2004.02.008 En ligne : https://doi.org/10.1016/j.rse.2004.02.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26764
in Remote sensing of environment > vol 91 n° 1 (15/05/2004) . - pp 68 - 89[article]Integrating imaging spectroscopy and neural networks to map grass quality in the Kruger National Park, South Africa / Onisimo Mutanga in Remote sensing of environment, vol 90 n° 1 (15/03/2004)
[article]
Titre : Integrating imaging spectroscopy and neural networks to map grass quality in the Kruger National Park, South Africa Type de document : Article/Communication Auteurs : Onisimo Mutanga, Auteur ; Andrew K. Skidmore, Auteur Année de publication : 2004 Article en page(s) : pp 104 - 115 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] Afrique du sud (état)
[Termes IGN] analyse comparative
[Termes IGN] azote
[Termes IGN] bande infrarouge
[Termes IGN] bande visible
[Termes IGN] erreur moyenne quadratique
[Termes IGN] herbe
[Termes IGN] image aérienne
[Termes IGN] image HYMAP
[Termes IGN] image hyperspectrale
[Termes IGN] régression linéaire
[Termes IGN] régression multiple
[Termes IGN] réseau neuronal artificiel
[Termes IGN] savaneRésumé : (Auteur) A new integrated approach, involving continuum-removed absorption features, the red edge position and neural networks, is developed and applied to map grass nitrogen concentration in an African savanna rangeland. Nitrogen, which largely determines the nutritional quality of grasslands, is commonly the most limiting nutrient for grazers. Therefore, the remote sensing of foliar nitrogen concentration in savanna rangelands is important for an improved understanding of the distribution and feeding patterns of wildlife. Continuum removal was applied on two absorption features located in the visible (R 550-757) and the SWIR (R 2015-2199) from an atmospherically corrected HYMAP MK1 image. A feature selection algorithm was used to select wavelength variables from the absorption features. Selected band depths from the absorption features as well as the red edge position (REP) were input into a backpropagation neural network. The best-trained neural network was used to map nitrogen concentration over the whole study area. Results indicate that the new integrated approach could explain 60% of the variation in savanna grass nitrogen concentration on an independent test data set, with a root mean square error (rmse) of 0. 13 (+ 8.3 0% of the mean observed nitrogen concentration). This result is better compared to the result obtained using multiple linear regression, which yielded an R of 38%, with a RMSE of 0.16 (+ 10.30% of the mean observed nitrogen concentration) on an independent test data set. The study demonstrates the potential of airborne hyperspectral data and neural networks to estimate and ultimately to map nitrogen concentration in the mixed species environments of Southern Africa. Numéro de notice : A2004-130 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.12.004 En ligne : https://doi.org/10.1016/j.rse.2003.12.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26657
in Remote sensing of environment > vol 90 n° 1 (15/03/2004) . - pp 104 - 115[article]Narrowband-to-broadband albedo conversion for glacier ice and snow: equations based on modeling and ranges of validity of the equations / W. Greuell in Remote sensing of environment, vol 89 n° 1 (15/01/2004)
[article]
Titre : Narrowband-to-broadband albedo conversion for glacier ice and snow: equations based on modeling and ranges of validity of the equations Type de document : Article/Communication Auteurs : W. Greuell, Auteur ; J. Oerlemans, Auteur Année de publication : 2004 Article en page(s) : pp 95 - 105 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] albedo
[Termes IGN] éclairement énergétique
[Termes IGN] erreur moyenne quadratique
[Termes IGN] glace
[Termes IGN] image Landsat-TM
[Termes IGN] image NOAA-AVHRR
[Termes IGN] image Terra-MISR
[Termes IGN] image Terra-MODIS
[Termes IGN] neige
[Termes IGN] réflectance
[Termes IGN] transfert radiatifRésumé : (Auteur) In this paper, we propose equations for narrowband-to-broadband (NTB) albedo conversion for glacier ice and snow for four types of satellite sensors : thematic mapper (TM), advanced very high resolution radiometer (AVHRR), moderate resolution imaging spectroradiometer (MODIS), and multi-angle imaging spectroradiometer (MISR). We do this on the basis of spectral albedos and incident spectral irradiances generated with radiative-transfer models of the (sub)surface (a two-stream model) and the atmosphere, respectively. First, we establish equations for reference values of atmospheric components and the surface elevation. These equations describe measurements with root-mean-square differences of ~0.016. We then show that the "reference equations" also perform well when total ozone and aerosol optical depth are changed with respect to the reference. The negative effect of humidity and elevation variations on the performance of the equations can be eliminated by adding a correction term. We argue that narrowband albedos are much less sensitive to variations in the incident spectral irradiance than broadband albedos. Hence, our conclusions about the effects of variations in atmospheric composition and elevation are also valid for equations for NTB conversion proposed in other papers. Numéro de notice : A2004-010 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.10.010 En ligne : https://doi.org/10.1016/j.rse.2003.10.010 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26538
in Remote sensing of environment > vol 89 n° 1 (15/01/2004) . - pp 95 - 105[article]Toward universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements / G. Le Maire in Remote sensing of environment, vol 89 n° 1 (15/01/2004)
[article]
Titre : Toward universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements Type de document : Article/Communication Auteurs : G. Le Maire, Auteur ; C. François, Auteur ; Eric Dufrêne, Auteur Année de publication : 2004 Article en page(s) : pp 1 - 28 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] albedo
[Termes IGN] chlorophylle
[Termes IGN] erreur moyenne quadratique
[Termes IGN] feuillu
[Termes IGN] indice de végétation
[Termes IGN] réflectance végétale
[Termes IGN] réseau neuronal artificielRésumé : (Auteur) Fifty-three leaves were randomly sampled on different deciduous tree species, representing a wide range of chlorophyll contents, tree ages, and leaf structural features. Their reflectance was measured between 400 and 800 nm with a 1-nm step, and their chlorophyll content determined by extraction. A larger simulated database (11,583 spectra) was built using the PROSPECT model, in order to test, calibrate, and obtain universal indices, i.e., indices applicable to a wide range of species and leaf structure. To our knowledge, almost all leaf chlorophyll indices published in the literature since 1973 have been tested on both databases. Fourteen canonical types of indices (published ones and new ones) were identified, and their wavelengths calibrated on the simulated database as well as on the experimental database to determine the best wavelengths and, hence, the best performances in chlorophyll estimation for each index types. These indices go from simple reflectance ratios to more sophisticated indices using reflectance first derivatives (using the Savitzky and Golay method). We also tested other nondestructive methods to obtain total chlorophyll concentration: SPAD (Minolta Camera, Osaka, Japan) and neural networks. The validity of the actual PROSPECT model is challenged by our results: Important discordances are found when the indices are calculated with PROSPECT compared to experimental data, especially for some indices and wavelengths. The discordance is even greater when the indices are determined with PROSPECT and applied on the experimental database. A new calibration of PROSPECT is therefore necessary for any study aiming at using simulated spectra to determine or to calibrate indices. The "peak jump" and the multiplepeak feature observed on the first derivative of the reflectances (e.g., in the Red-Edge Inflection Point [REIP] index) has been investigated. It was shown that chlorophyll absorption alone can explain this feature. The peak jump disqualifies the REIP to be a valuable chlorophyll index. A simple modified difference ratio gave the best results among all published indices (cross-validated RMSE 2.1 [ug/cm2 on the experimental database). After calibration on the experimental database, modified Simple Ratio (mSR) and modified Nonnalized Difference (mND) indices gave the best performances (RMSECV = 1. 8 ug/cm2 on the experimental database). The new Double Difference (DD) index, although not the best on the experimental database (RMSECV = 2.9 [ug/cm2), has the best results on the larger simulated database (RMSE = 3.7 gg/cm2 ) and is expected to give good results on larger experimental databases. The best reflectance-based indices give better performances than the current commercial nondestructive device SPAD (RMSECV = 4.5 ug/cm2). In this leaf-level study, the best indices are very near from each other, so that complex methods are useless: REIP-like, neural networks, and derivative-based indices are not necessary and give worst results than simpler properly chosen indices. These conclusions will certainly be different for a canopy-level study, where the derivative-based indices may perform significantly better than the other ones. Numéro de notice : A2004-008 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.09.004 En ligne : https://doi.org/10.1016/j.rse.2003.09.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26536
in Remote sensing of environment > vol 89 n° 1 (15/01/2004) . - pp 1 - 28[article]Evaluation de la qualité des bases de données géographiques de référence à la communauté urbaine de Bordeaux / Yann Sorton (2004)
Titre : Evaluation de la qualité des bases de données géographiques de référence à la communauté urbaine de Bordeaux Type de document : Mémoire Auteurs : Yann Sorton, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2004 Importance : 47 p. Format : 21 x 30 cm Note générale : Bibliographie
Rapport de stage pluridisciplinaire, cycle des ingénieurs diplômés de l'ENSG 2ème année (IT2)Langues : Français (fre) Descripteur : [Vedettes matières IGN] Bases de données localisées
[Termes IGN] actualité des données
[Termes IGN] analyse des besoins
[Termes IGN] base de données localisées
[Termes IGN] Bordeaux
[Termes IGN] catalogue de données localisées
[Termes IGN] cohérence logique
[Termes IGN] communauté urbaine
[Termes IGN] erreur moyenne quadratique
[Termes IGN] évaluation
[Termes IGN] exhaustivité des données
[Termes IGN] précision géométrique (imagerie)
[Termes IGN] précision sémantique
[Termes IGN] qualité des données
[Termes IGN] Star-APIC
[Termes IGN] système d'information géographiqueIndex. décimale : PROJET Mémoires : Rapports de projet - stage des ingénieurs de 2e année Résumé : (Auteur) L'objectif de ce stage fut d'analyser les bases de données géographiques de la Communauté Urbaine de Bordeaux afin d'en évaluer la qualité. Cette véritable mission d'expertise répondait à un réel besoin de la part de la Direction des Données Géoréférencées, soucieuse d'informer les utilisateurs sur la qualité de ces données. La première étape fut le choix des bases à évaluer et des critères à analyser: En effet, les bases de données de la CUB sont extrêmement diverses, par leur contenu, leur gestion, leur utilisation. Deux bases de données ont été sélectionnées, toutes deux produites par les services communautaires, et sûrement les plus représentatives du SIG de la CUB : le Filaire de Voie, et le Domaine Public. Tous les éléments de ces bases ont été passés au crible, et une évaluation de la cohérence logique, de la précision géométrique (ponctuelle), de la précision sémantique, de l'exhaustivité et de l'actualité des données a été réalisée. Enfin, dans un souci de communication sur ce SIG qui semblait si complexe aux yeux de nombre d'utilisateurs, un catalogue a été réalisé pour l'ensemble des bases de données de référence de la CUB. Numéro de notice : 30123 Affiliation des auteurs : IGN (1940-2011) Thématique : GEOMATIQUE/INFORMATIQUE Nature : Mémoire de projet pluridisciplinaire Organisme de stage : Communauté Urbaine de Bordeaux CUB Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=51627 Réservation
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