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Tree species classification using within crown localization of waveform LiDAR attributes / Rosmarie Blomley in ISPRS Journal of photogrammetry and remote sensing, vol 133 (November 2017)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 133 (November 2017) . - pp 142 - 156 Titre : Tree species classification using within crown localization of waveform LiDAR attributes Type de document : Article/Communication Auteurs : Rosmarie Blomley, Auteur ; Aarne Hovi, Auteur ; Martin Weinmann, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 142 - 156 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] analyse multiéchelle [Termes IGN] Betula pendula [Termes IGN] betula pubescens [Termes IGN] croissance des arbres [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] espèce végétale [Termes IGN] extraction de traits caractéristiques [Termes IGN] forêt boréale [Termes IGN] Norvège [Termes IGN] Picea abies [Termes IGN] Pinus sylvestris [Termes IGN] rotation d'objet Résumé : (Auteur) Since forest planning is increasingly taking an ecological, diversity-oriented perspective into account, remote sensing technologies are becoming ever more important in assessing existing resources with reduced manual effort. While the light detection and ranging (LiDAR) technology provides a good basis for predictions of tree height and biomass, tree species identification based on this type of data is particularly challenging in structurally heterogeneous forests. In this paper, we analyse existing approaches with respect to the geometrical scale of feature extraction (whole tree, within crown partitions or within laser footprint) and conclude that currently features are always extracted separately from the different scales. Since multi-scale approaches however have proven successful in other applications, we aim to utilize the within-tree-crown distribution of within-footprint signal characteristics as additional features. To do so, a spin image algorithm, originally devised for the extraction of 3D surface features in object recognition, is adapted. This algorithm relies on spinning an image plane around a defined axis, e.g. the tree stem, collecting the number of LiDAR returns or mean values of returns attributes per pixel as respective values. Based on this representation, spin image features are extracted that comprise only those components of highest variability among a given set of library trees. The relative performance and the combined improvement of these spin image features with respect to non-spatial statistical metrics of the waveform (WF) attributes are evaluated for the tree species classification of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and Silver/Downy birch (Betula pendula Roth/Betula pubescens Ehrh.) in a boreal forest environment. This evaluation is performed for two WF LiDAR datasets that differ in footprint size, pulse density at ground, laser wavelength and pulse width. Furthermore, we evaluate the robustness of the proposed method with respect to internal parameters and tree size. The results reveal, that the consideration of the crown-internal distribution of within-footprint signal characteristics captured in spin image features improves the classification results in nearly all test cases Numéro de notice : A2017-724 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2017.08.013 En ligne : https://doi.org/10.1016/j.isprsjprs.2017.08.013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=88409 [article]

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Towards an enhanced understanding of airborne LiDAR measurements of forest vegetation / Aarne Hovi (2015)  

Public Titre : Towards an enhanced understanding of airborne LiDAR measurements of forest vegetation Type de document : Thèse/HDR Auteurs : Aarne Hovi, Auteur Editeur : Vantaa [Finlande] : Finnish Society of Forest Science Année de publication : 2015 Collection : Dissertationes forestales, ISSN 1795-7389 num. 200 Format : 21 x 30 cm ISBN/ISSN/EAN : 978-951-651-489-8 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] analyse de sensibilité [Termes IGN] composition d'un peuplement forestier [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] espèce végétale [Termes IGN] forme d'onde [Termes IGN] identification automatique [Termes IGN] photogrammétrie terrestre [Termes IGN] signal laser Résumé : (auteur) This thesis presents basic research on how airborne LiDAR measurements of forest vegetation are influenced by the interplay of the geometric-optical properties of vegetation, sensor function and acquisition settings. Within the work, examining the potential of waveform (WF) recording sensors was of particular interest. Study I focused upon discrete return LiDAR measurements of understory trees. It showed that transmission losses influenced the intensity of observations and echo triggering probabilities, and also skewed the distribution of echoes towards those triggered by highly reflective or dense targets. The intensity data were of low value for species identification, but the abundance of understory trees could be predicted based on echo height distributions. In study II, a method of close-range terrestrial photogrammetry was developed. Images were shown as being useful for visualizations and even the geometric quality control of LiDAR data. The strength of backscattering was shown to correlate with the projected area extracted from the images. In study III, a LiDAR simulation model was developed and validated against real measurements. The model was able to be used for sensitivity analyses to illustrate how plant structure or different pulse properties influence the WF data. Both simulated and real data showed that WF data were able to capture small-scale variations in the structural and optical properties of juvenile forest vegetation. Study IV illustrated the potential of WF data in the species classification of larger trees. The WF features that separated tree species were also dependent on other variables such as tree size and phenology. Inherent between-tree differences in structure were quantified and the effects of pulse density on the features were examined. Overall, the thesis provides basic findings on how LiDAR pulses interact with forest vegetation, and serves to link theory with real observations. The results contribute to an improved understanding of LiDAR measurements and their limitations, and thus provide support for further improvements in both data interpretation methods and specific sensor design. Numéro de notice : 14979 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Thèse étrangère Note de thèse : PhD : Forest sciences : University of Helsinki : 2015 En ligne : http://www.metla.fi/dissertationes/df200.htm Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=78367

Backscattering of individual LiDAR pulses from forest canopies explained by photogrammetrically derived vegetation structure / Ilkka Korpela in ISPRS Journal of photogrammetry and remote sensing, vol 83 (September 2013)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 83 (September 2013) . - pp 81 - 93 Titre : Backscattering of individual LiDAR pulses from forest canopies explained by photogrammetrically derived vegetation structure Type de document : Article/Communication Auteurs : Ilkka Korpela, Auteur ; Aarne Hovi, Auteur ; Lauri Korhonen, Auteur Année de publication : 2013 Article en page(s) : pp 81 - 93 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] appariement de lignes [Termes IGN] canopée [Termes IGN] diffusion du rayonnement [Termes IGN] forêt [Termes IGN] impulsion laser [Termes IGN] photogrammétrie métrologique [Termes IGN] photogrammétrie terrestre [Termes IGN] rétrodiffusion [Termes IGN] signal lidar Résumé : (Auteur) In recent years, airborne LiDAR sensors have shown remarkable performance in the mapping of forest vegetation. This experimental study looks at LiDAR data at the scale of individual pulses to elucidate the sources behind interpulse variation in backscattering. Close-range photogrammetry was used for obtaining the canopy reference measurements at the ratio scale. The experiments illustrated different orientation techniques in the field, LiDAR acquisitions and photogrammetry in both leaf-on and leaf-off conditions, and two-waveform recording LiDAR sensors. The intrafootprint branch silhouettes in zenith-looking images, in which the camera, footprint, and LiDAR sensor were collinear, were extracted and contrasted with LiDAR backscattering. An enhanced planimetric match (refinement of strip matching) was achieved by shifting the pulses in a strip and searching for the maximal correlation between the silhouette and LiDAR intensity. The relative silhouette explained up to 80–90% of the interpulse variation. We tested whether accounting for the Gaussian spread of intrafootprint irradiance would improve the correlations, but the effect was blurred by small-scale geometric noise. Accounting for receiver gain variations in the Leica ALS60 sensor data strengthened the dependences. The size of the vegetation objects required for triggering a LiDAR observation was analyzed. We demonstrated the use of LiDAR pulses adjacent to canopy vegetation, which did not trigger a canopy echo, for canopy mapping. Pulses not triggering an echo constitute the complement to the actual canopy. We conclude that field photogrammetry is a useful tool for mapping forest canopies from below and that quantitative analysis is feasible even at the scale of single pulses for enhanced understanding of LiDAR observations from vegetation. Numéro de notice : A2013-489 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2013.06.002 En ligne : https://doi.org/10.1016/j.isprsjprs.2013.06.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32627 [article]

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