Il existe au Québec un cadastre vertical qui montre graphiquement la propriété dans le cas de la superposition de la propriété. De nombreux travaux se sont intéressés au besoin d'une représentation volumique cadastrale pour ce type de cas, mais peu d'études ont porté sur la question de l'acquisition des données. Nous nous intéressons ici à l'utilisation des LiDAR terrestres pour la modélisation 2D et 3D à des fins cadastrales, technique peu utilisée aujourd'hui pour ce type d'application. L'objectif est d'estimer la pertinence du LiDAR terrestre pour l'acquisition de données spatiales utiles à la production de représentations cadastrales 2D et 3D pour des condominiums. Cette étude, en collaboration avec le groupe VRSB, a porté sur deux cas réels de condominiums et a permis, via la comparaison de levés effectués au LiDAR terrestre et au distancemètre, de mettre en évidence les avantages et les inconvénients du LiDAR terrestre pour cette application.

Des études récentes ont montré qu'avec l'aide des scènes créées à partir d'environnements naturels tels que les forêts, nous pouvons avoir un impact significatif sur la réduction voire l'amélioration des symptômes de diverses maladies, dont la plus importante est la maladie d'Alzheimer. Les effets de ces études ont été recherchés au fil des ans et des résultats très prometteurs ont été obtenus. De nos jours, l'une des choses qui peut être très étonnante et intéressante est l'expérience de ces environnements naturels par la synthèse des scènes informatiques, notamment via les environnements de réalité virtuelle. Plus le niveau d'immersion de ces environnements naturels conçus en réalité virtuelle est élevé et meilleur, plus il peut contribuer à améliorer les symptômes du patient. L'une des méthodes nouvelles et innovantes pour concevoir et construire des environnements naturels tels que les forêts est l'utilisation de données des scanners laser, qui nous fournissent des résultats très réalistes. Pour cette raison, dans cette étude, nous présentons une forêt virtuelle dérivée de données LiDAR terrestre et améliorée grâce à des techniques d'effets spéciaux.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2009-2010 / La télédétection satellitaire offre de nouvelles promesses pour le suivi à grande échelle de territoires reculés, mais les capteurs multispectraux généralement utilisés pour ce type d’étude n’offrent pas une information suffisamment détaillée. Les capteurs lidar apportent une nouvelle vision des écosystèmes forestiers, par leur capacité à mesurer directement la structure verticale des éléments recouvrant le sol. Une méthode tirant avantage de ce type de données a été développée pour permettre de répondre à la problématique du suivi de la biomasse aérienne des écosystèmes forestiers du Québec, qui couvrent une superficie de 1.3 M Km2. Des équations allométriques permettent d’estimer la biomasse aérienne sèche pour l’ensemble des arbres d’une placette d’inventaire et le contenu en carbone équivaut à 50% de cette biomasse. À l’aide de données provenant d’un capteur lidar profileur aérien, une équation générique permettant d’estimer la biomasse de ces placettes a été développée (R2 = 0.65, n=207). Puis, en utilisant une carte de couverture du sol Landsat ETM+ et une carte des zones de végétation, des équations ont aussi été développées pour des strates représentant trois types de couverts forestiers répartis dans trois grandes zones de végétation (R2 variant de 0.51 à 0.79). Le système lidar aérien a aussi survolé quatre portions d’orbite du Geoscience Laser Altimetry System (GLAS), à bord du satellite ICESat. Les données de ces orbites du GLAS et d’un modèle numérique d’élévation SRTM ont été utilisées pour développer une équation permettant de prédire la biomasse aérienne sèche estimée par le lidar aérien (R2 = 0.59, n=1325). Les résultats obtenus de cette régression nous ont permis d’utiliser les 104 044 impulsions lidar de GLAS disponibles pour la zone d’étude pour estimer la biomasse aérienne sèche totale tant pour les principales zones de végétation que pour la zone d’étude en entier. Pour la zone d’étude, la biomasse est en moyenne de 39.0  2.2 (erreur type) Mg ha-1 pour un total de 4.9  0.3 Pg et sa distribution parmi les zones de végétation principales au Québec est 12.6% feuillus nordiques, 12.6% mélangés nordiques, 38.4% boréale commerciale, 13% boréale non-commerciale, 14.2% taïga, et 9.2% toundra arborée. Les forêts non-commerciales représentent 36% de la biomasse aérienne estimée alors que les forêts boréales représentent 51% de cette biomasse. / A method to estimate aboveground dry biomass of Quebec’s forest ecosystems was developed using data from a spaceborn lidar. The study area covers the portion of the province south of the treeline, an area of 1.3 M Km2. Biomass was first estimated for ground inventory plots using allometric equations. A small footprint laser profiler then flew over these inventory plots to develop a generic airborne lidar-based biomass equation (R2 = 0.65, n=207). As well, the Landsat ETM+ land cover map and the vegetation zone maps were used to develop stratified equations (R2 ranging between 0.51 and 0.79). The same airborne lidar system flew along four portions of orbits of the ICESat Geoscience Laser Altimeter System (GLAS). An equation was developed to predict airborne profiling lidar estimates of aboveground dry biomass from GLAS data and from the SRTM digital elevation model (R2 = 0.59, n=1325). These results allowed us to use the 104,044 GLAS pulses available over the study area to estimate the total aboveground dry biomass for the main vegetation areas of Quebec as well as for the entire study area. Biomass for the entire study area averaged 39.0  2.2 (standard error) Mg ha-1 and totalled 4.9  0.3 Pg with 36% of this biomass located in non-commercial forests and 51% located in the boreal forest (both commercial and non-commercial).

Les marais salés de la Baie du Mont-Saint-Michel forment un écosystème complexe et fragile. Afin de mieux comprendre l'organisation spatiale de la végétation de ces marais et de développer une vision synthétique de la dynamique de ce milieu, des données de télédétection optiques (orthophotographie) et altimétrique (LiDAR), ainsi que des observations de terrain ont été réunies et traitées conjointement. Le contrôle qualité des données LiDAR ayant mis en évidence un biais systématique dépendant de la hauteur et de la densité de la végétation, une correction, consistant à assigner à chaque pixel la valeur LIDAR minimale au sein d'un carré de 3x3 m, a été appliquée. Une importante base de données spatialisées a ensuite été constituée, comprenant la description en termes de végétation, d'altitude, de géomorphologie, de sédimentologie et d'utilisation agricole de près de 10 000 points d'observation répartis sur l'ensemble de la Baie. Des analyses fréquentielles ont permis de quantifier les liaisons entre les différentes espèces végétales, afin de définir les associations végétales caractéristiques des marais salés. Cette méthode a également permis de dresser la liste exhaustive des liaisons statistiques entre toutes les espèces végétales de la Baie du Mont-Saint-Michel et quatre facteurs écologiques : l'altitude, la géomorphologie, le contexte sédimentaire et le pâturage. Les variations de l'altitude moyenne des espèces végétales à l'échelle de la Baie s'expliquent par l'existence d'une double pente hydraulique qui engendre des altitudes plus élevées à l'Est et à l'Ouest de la Baie. Le contexte géomorphologique et le pâturage peuvent également modifier les valeurs d'altitude moyenne des espèces végétales, et profondément perturber le schéma classique des marais salés. La connaissance des liaisons entre les espèces végétales et les valeurs des facteurs écologiques peut constituer une aide importante à la cartographie des marais salés / In the Mont-Saint-Michel bay, the tidal salt marshes, also called schorre, are made up of low and dense vegetation, that is adapted to tidal flooding and high salinity, and that spreads quickly on the upper tidal flat. The study of this phenomenon requires a map of the vegetation and a simple way to update it. The aim of this study is to evaluate the potential of LiDAR data to enhance the comprehension of this ecosystem. The LiDAR data was first corrected from the systematic error due to the low vegetation that stops the laser beams before they reach the ground. A spatial data base was then created from 9811 observation points, including information on vegetation, altimetry, geomorphology, sedimentology and land use. Frequency analyses were performed on three locations characterized by different geomorphology, sedimentology and land use contexts, and in a second time at the scale of the entire Bay. The vegetation associations of the salt marsh were described, and the relations between each plant species and four ecological factors (altimetry, geomorphology, sedimentology and land use) were investigated. This study has shown the need to include in the mapping process of salt marsh vegetation LiDAR data as well as information on geomorphology, sedimentology and land use

[pt] Objetivo. Fornecer confiabilidade às medições do LIDAR a partir: (i) do estabelecimento de padrões de configuração dos parâmetros do equipamento, na obtenção de sinais de fluorescência para medições de pigmentos em água; (ii) da avaliação de diferentes procedimentos para melhorar a relação sinal-ruído, preservando a integridade das bandas de interesse contidas no espectro de fluorescência; (iii) da verificação da repetitividade do equipamento para medições de comprimentos de onda associados aos máximos do espalhamento Raman da água, da banda de clorofila a, assim como, da banda de matéria orgânica dissolvida (MOD); (iv) e da avaliação da eficiência do processamento desenvolvido para obtenção de concentrações relativas da clorofila a quando comparadas aos resultados correlacionados à concentrações absolutas desse tipo de pigmento. Motivação. Contribuir para o desenvolvimento do monitoramento remoto utilizando um sistema LIDAR, fornecendo parâmetros que possibilitem maior confiabilidade às informações adquiridas pelo sistema. Contextualização. O monitoramento ambiental é uma prática adotada com maior freqüência por inúmeras empresas e instituições com o objetivo de minimizar impactos nocivos ao meio ambiente. O monitoramento remoto é uma ótima alternativa, pois, possibilita um levantamento prévio de possíveis vazamentos de diferentes tipos de poluição, sendo sensível à avaliação de sutis alterações no meio, possibilitando a identificação desses problemas antes mesmo de se tornarem aparentes. Metodologia. A prática adotada na obtenção de êxito dos objetivos apontados baseou-se: (i) na coleta de informação de diferentes modelos de monitoramento remoto, principalmente, utilizando um sistema LIDAR; (ii) na coleta de dados através da experimentação em laboratório e em campo e (iii) no desenvolvimento de processos que possibilitaram a análise das informações contidas nos sinais obtidos. Resultados. Na busca de um sinal-padrão de resposta do equipamento, o trabalho consiste em análises experimentais e no desenvolvimento de processos que auxiliem na análise das informações contidas nos sinais. Dentre os experimentos pode-se destacar duas abordagens: (i) a primeira, no laboratório, a partir de análise de amostras de água pura, que avalia as flutuações do sinal de fluorescência do espalhamento Raman da água para diferentes parâmetros do equipamento; (ii) e uma segunda análise, com dados in vivo, que avalia a concentração relativa de clorofila a para diferentes processos a fim de obter um processo padrão que diminui a sua incerteza na determinação desse quantitativo. Conclusões. O sensoriamento retomo é uma técnica útil para a investigação ambiental, porém, a implantação de práticas que contribuem para o aumento da confiabilidade dos dados fornecidos pelo sistema são igualmente indispensáveis. / [en] Aim. Providing reliability of LIDAR readings of fluorescence signals for measurements of pigments in ocean water by: (i) establishing configuration standards for equipment parameters. (ii) assessing different procedures to improve the signal-tonoise relationship. (iii) preserving the integrity of the wavelength bandwidth of the fluorescence spectrum. (iv) verifying the repeatability of wavelength measurements associated with local maxima of the Raman scattering curve of ocean water and chlorophyll a, as well as organic materials (dissolved in water) bandwidths. (v) and assessing the efficiency of the methodology developed for obtaining relative concentrations of chlorophyll a. Motivation. Contributing to the development of remote monitoring when using the LIDAR technique. This would bring about greater reliability. Context. Over the years environmental surveillance has been adopted by many companies and institutions as an effective practice to minimize harmful impacts on the environment. The remote monitoring is unquestionably a versatile alternative for detecting possible leaking of noxious substances before they become apparent. Methodology. The procedures included: (i) collecting information of different physical models of remote monitoring. (ii) collecting data from experiments carried out in the laboratory and in situ. (iii) and developing a procedure to analyze signal information. Results. Two approaches were adopted when carrying out the experiments: (i) in the laboratory, by evaluating fluorescence signal fluctuations of the Raman scattering in ocean water for different equipment parameters. (ii) and in situ, by measuring the relative concentration of chlorophyll a in ocean water for different schemes in order to choose the standard one. Conclusions. The remote monitoring is a useful tool to carry out environmental surveillance. But to increase the reliability of data collected by the optical-laser system apparatus the introduction of metrological assessment procedures is mandatory.

There is a range of detailed research on edge effects using field data at local scales. However, the scientific literature lacks studies that aim to understand its characteristics in forest fragments using larger scales. Also, few works have considered the influences that each fragment of the landscape imposes on its neighbour. Since biological processes linked to fragmentation and degradation commonly start at edges and influence the dynamics of forest communities, studies on edge effects are crucial for the development of management and conservation plans. Lidar technologies have been used in several studies on forest structure, but few have investigated edge effects. This dissertation presents two distinct applications of lidar for studying anthropogenic-caused edges in different scenarios and ecosystems. In the first study, edge effects in commercial Eucalyptus plantations and fragments of the Atlantic Forest, located in the State of São Paulo, were evaluated by quantifying the differences in height and understory density in the edge vegetation vs core. We also sought to understand the influences that each type of adjacent fragment (Eucalyptus, native forest or pasture) imposes on the neighbouring vegetation. Edge effects, regarding height and understory density, on fragments of native vegetation adjacent to Eucalyptus plantations and vice-versa were more attenuated than nearby pastures. The results indicated that the protection of native forests in silviculture areas besides favouring the maintenance of local ecosystem services (provision and maintenance of water flow, diversity of flora and fauna species, natural pest control, etc.) could help maintain the homogeneity of the stands due to their ability to minimise edge effects. This protection could favour the occurrence of border Eucalyptus more similar to the ones in the core. In the second study, edge effects caused by seismic lines, i.e. corridors cut through the forest during the process of exploration of gas and oil, in areas of Boreal Forest in the central region of Alberta is addressed. Besides quantifying the effects of distance from seismic lines over height and fractional cover on the neighbouring vegetation, the interactions between these variables and primary vegetation growth factors related to the topographic position, incident radiation and surface geology were evaluated. The results showed that significant changes in vegetation structure adjacent to forest edge occur close to seismic lines, including reduced tree height and cover. Random Forest analyses revealed that the distance from the seismic line, incident radiation and surface water accumulation potential (inferred from the topographic position index) are the most critical variables for height and fractional cover prediction. Overall, lidar proved to be a robust tool for assessing the spatial and ecological dimensions of edge effects in different scenarios. With this in mind, management and conservation strategies for fragmented areas could benefit from this technology to reduce the impact from edge effects on ecosystems. / Há uma gama de pesquisas detalhadas sobre efeitos de borda usando dados de campo em escalas locais. No entanto, a literatura científica carece de trabalhos que visem compreender suas características em fragmentos florestais utilizando escalas maiores. Além disso, poucos estudos levaram em conta as influências que cada fragmento da paisagem impõe sobre seu vizinho. Uma vez que processos biológicos ligados à fragmentação e degradação geralmente se iniciam pelas bordas e influenciam a dinâmica das comunidades florestais, estudos sobre efeitos de borda são cruciais para o desenvolvimento de planos de manejo e conservação. Tecnologias lidar têm sido usadas em diversos estudos sobre a estrutura de florestas, mas poucos trabalhos investigaram efeitos de borda. Esta dissertação apresenta duas aplicações distintas do lidar para o estudo de bordas criadas pelo homem em diferentes cenários e ecossistemas. No primeiro estudo, efeitos de borda em plantios comerciais de eucalipto e fragmentos de Mata Atlântica, no Estado de São Paulo, foram avaliados por meio da quantificação das diferenças na altura e densidade do sub-bosque na vegetação da borda vs. interior. Buscou-se também compreender as influências que cada tipo de fragmento adjacente (eucalipto, floresta nativa ou pasto) impõe sobre a vegetação vizinha. Os efeitos de borda, em termos de altura e densidade do sub-bosque, em fragmentos de vegetação nativa adjacentes aos plantios de eucalipto e vice-versa foram mais atenuados do que próximo às pastagens. Os resultados indicaram que a proteção de florestas nativas em áreas de silvicultura além de favorecer a manutenção de serviços ecossistêmicos locais (provisão e manutenção do fluxo de água, diversidade de espécies da flora e fauna, controle natural de pragas etc.) poderia ajudar a manter a homogeneidade dos talhões devido à sua capacidade de minimizar os efeitos de borda. Esta proteção poderia favorecer a ocorrência de eucaliptos de borda mais semelhantes aos de interior. No segundo estudo, foram abordados efeitos de borda causados pela abertura de linhas sísmicas durante o processo de exploração de gás e petróleo em áreas de Floresta Boreal, na região central de Alberta. Além da quantificação dos efeitos da distância das linhas sísmicas na altura e cobertura arbórea da vegetação vizinha, foram avaliadas as interações entre tais variáveis e fatores de crescimento primário da vegetação relacionados a posição topográfica, radiação e superfície geológica. Os resultados mostraram que variações significativas na estrutura da vegetação adjacente à borda da floresta ocorrem próximas às linhas sísmicas, incluindo altura e cobertura arbórea reduzidas. Análises por meio de florestas aleatórias (random forest) revelaram que a distância da linha sísmica, a radiação incidente e o potencial de acumulação de água superficial (inferida a partir do índice de posição topográfica) são as variáveis mais importantes para predição de altura e cobertura arbórea. No geral, o lidar se mostrou uma ferramenta robusta para avaliar as dimensões espaciais e ecológicas dos efeitos de borda em diferentes cenários. Com isso em mente, estratégias de manejo e conservação para áreas fragmentadas poderiam se beneficiar desta tecnologia para redução do impacto de efeitos de borda nos ecossistemas.

Sensors based on LiDAR (Light Detection and Ranging) technology have the potential to provide accurate 3D models of the trees retrieving information such as canopy volume and height. This information can be used for diagnostics and prescriptions of fertilizers and plant protection products on a site-specific basis. This research aimed to investigate the use of LiDAR sensors in orange crops. Orange is one of the most important tree crop in Brazil. So far, research have developed and tested LiDAR based systems for several tree crops. However, usually individual trees or small field plots have been used. Therefore, several aspects related to data acquisition and processing must still be developed for large-scale application. The first study reported in this document (Chapter 3) aimed to develop and test a mobile terrestrial laser scanner (MTLS) and new data processing methods in order to obtain 3D models of large commercial orange groves and spatial information about canopy geometry. A 2D laser sensor and a RTK-GNSS receiver (Real Time Kinematics - Global Navigation Satellite System) were mounted on a vehicle. The data processing was based on generating a georeferenced point cloud, followed by the filtering, classification and surface reconstruction steps. A 25 ha commercial orange grove was used for field validation. The developed data acquisition and processing system was able to produce a reliable point cloud of the grove, providing high resolution canopy volume and height information. The choice of the type of point cloud classification (by individual trees or by transversal sections of the row) and the surface reconstruction algorithm is discussed in this study. The second study (Chapter 4) aimed to characterize the spatial variability of canopy geometry in commercial orange groves. Understanding such variability allows sensor-based variable rate application of inputs (i.e, applying proportional rates of inputs based on the variability of canopy size) to be considered as a suitable strategy to optimize the use of fertilizers and plant protection products. Five commercial orange groves were scanned with the developed MTLS system. According to the variability of canopy volume found in those groves, the input savings as a result of implementing sensor-based variable rate technologies were estimated in about 40%. The second goal of this study was to understand the relationship between canopy geometry and several other relevant attributes of the groves. The canopy volume and height maps of three groves were analyzed against historical yield maps, elevation, soil electrical conductivity, organic matter and clay content maps. The correlations found between canopy geometry and yield or soil maps varied from poor to strong correlations, depending on the grove. When classifying the groves into three classes according to canopy size, the yield performance and soil features inside each class was found to be significantly different, indicating that canopy geometry is a suitable variable to guide management zones delineation in one grove. Overall results from this research show the potential of MTLS systems and subsequent data analysis in orange crops indicating how canopy geometry information can be used in site-specific management practices. / Sensores baseados em tecnologia LiDAR (Light Detection and Ranging) têm o potencial de fornecer modelos tridimensionais de árvores, provendo informações como o volume e altura de copa. Essas informações podem ser utilizadas em diagnósticos e recomendações localizadas de fertilizantes e defensivos agrícolas. Este estudo teve como objetivo investigar o uso de sensores LiDAR na cultura da laranja, uma das principais culturas de porte arbóreo no Brasil. Diversas pesquisas têm desenvolvido sistemas LiDAR para culturas arbóreas. Porém, normalmente tais sistemas são empregados em plantas individuais ou em pequenas áreas. Dessa forma, diversos aspectos da aquisição e processamento de dados ainda devem ser desenvolvidos para viabilizar a aplicação em larga escala. O primeiro estudo deste documento (Capítulo 3) focou no desenvolvimento de um sistema LiDAR (Mobile Terrestrial Laser Scanner - MTLS) e nova metodologia de processamento de dados para obtenção de informações acerca da geometria das copas em pomares comerciais de laranja. Um sensor a laser e um receptor RTK-GNSS (Real Time Kinematics - Global Navigation Satellite System) foram instalados em um veículo para leituras em campo. O processamento de dados foi baseado na geração de uma nuvem de pontos, seguida dos passos de filtragem, classificação e reconstrução da superfície das copas. Um pomar comercial de laranja de 25 ha foi utilizado para a validação. O sistema de aquisição e processamento de dados foi capaz de produzir uma nuvem de pontos representativa do pomar, fornecendo informação sobre geometria das plantas em alta resolução. A escolha sobre o tipo de classificação da nuvem de pontos (em plantas individuais ou em seções transversais das fileiras) e sobre o algoritmo de reconstrução de superfície, foi discutida nesse estudo. O segundo estudo (Capítulo 4) buscou caracterizar a variabilidade espacial da geometria de copa em pomares comerciais. Entender tal variabilidade permite avaliar se a aplicação em taxas variáveis de insumos baseada em sensores LiDAR (aplicar quantias de insumos proporcionais ao tamanho das copas) é uma estratégia adequada para otimizar o uso de insumos. Cinco pomares comerciais foram avaliados com o sistema MTLS. De acordo com a variabilidade encontrada, a economia de insumos pelo uso da taxa variável foi estimada em aproximadamente 40%. O segundo objetivo desse estudo foi avaliar a relação entre a geometria de copa e diversos outros parâmetros dos pomares. Os mapas de volume e altura de copa foram comparados aos mapas de produtividade, elevação, condutividade elétrica do solo, matéria orgânica e textura do solo. As correlações entre geometria de copa e produtividade ou fatores de solo variaram de fraca até forte, dependendo do pomar. Quando os pomares foram divididos entre três classes com diferentes tamanhos de copas, o desempenho em produtividade e as características do solo foram distintas entre as três zonas, indicando que parâmetros de geometria de copa são variáveis úteis para a delimitação de unidades de gestão diferenciada em um pomar. Os resultados gerais desta pesquisa mostraram o potencial de sistemas MTLS para pomares de laranja, indicando como a geometria de copa pode ser utilizada na gestão localizada de pomares de laranja.

No âmbito das mudanças climáticas globais, a quantificação do estoque de carbono em povoamentos florestais tem recebido mais atenção, principalmente pelo fato das florestas exercerem um papel fundamental no equilíbrio do estoque de carbono global. Com o objetivo de contribuir para esse processo, a parte investigativa deste trabalho foi desenvolvida em duas etapas. A primeira etapa objetivou o ajuste de modelos alométricos para a estimativa do estoque de carbono presente na biomassa total (Ctotal), no lenho comercial (Cleco) e parte residual (Crds) (casca, folhas e galhos) em plantações de Eucalyptus spp. em nível de árvores, através de uma amostragem destrutivas de árvores, análise elementar do carbono em laboratório e medidas convencionais de inventário. A medição do diâmetro à altura do peito (DAP) e altura total das árvores em parcelas amostradas instaladas nos talhões onde as árvores foram coletadas para determinação direta de carbono também foi realizada. A segunda parte, consistiu na avaliação do uso da tecnologia LiDAR (Light Detection and Ranging) aerotransportada (Airborne LASER scanning) como uma alternativa eficiente e versátil para a estimativa do estoque de carbono total (Ctotal), no lenho comercial de toras (Cleco) e no resíduo da árvore (Crds) em nível de parcelas em plantações de Eucalyptus spp usando como base o estoque de carbono estimado na primeira fase. Os resultados obtidos encontram-se resumidos em dois artigos científicos. O primeiro artigo mostra que os modelos baseados no logaritmo do diâmetro à altura do peito (DAP) e da altura total da árvore (Ht) oferecem boas precisão e exatidão para estimar o estoque de carbono em nível de árvore. O segundo artigo, permitiu a determinação das melhores métricas LiDAR para o cálculo do teor total de carbono, tanto no carbono total, lenho comercial e nas partes residuais da árvore em nível de plantação. Esses resultados, bem como os indicadores estatísticos utilizados para avaliar a qualidade dos ajustes, são o cerne desta dissertação. / In the context of global climate change, the quantification of the carbon content in forest plantations have received great attention. This is because vegetation play an important role in the global carbon budget. This master thesis was developed in two main parts. The first part was to adjust allometric equations for the estimation of the carbon content at a tree level. This was performed for the above ground section (Ctotal), in commercial logs (Cleco) and residuals ( Crds) (e.g. bark, leaves and branches/twigs). The experiment was based on the destructive model of individual trees harvested in commercial plantations of Eucaliptus spp. The experiment encompasses both forest inventory and laboratory analyses procedures. Additionally, in-situ measurements such as the diameter at the breast height (DBH) and the total tree height were also performed. These sample plots were located in homogeneous forest units and close to the areas were the trees have been harvested. The second part of this master thesis was the evaluation of the airborne LiDAR technology as a tool for the retrieval of the above ground biomass (Ctotal), the carbon present in the commercial logs (Cleco) and residuals. This procedure was performed at the sample plots level. This procedure was based on the information provided in the first part. The results are presented as two scientific manuscripts. The first manuscript shows that allometric equations based on the log of the variables diameter at the breast height (DBH) and total tree height (Ht) were good predictors for the retrieval of the total carbon content at a tree level. The second manuscript allow the selection of the best LiDAR derived metrics for the retrieval of the total carbon content, either at above ground level, commercial logs and residual parts of the tree at a sample plots level. These results, as well as the statistical indicators for the adjustment of several statistical models is the core of this master thesis.

Parce que les processus nuageux sont des processus complexes qui opèrent à des échelles spatiales très différentes, l'évolution de l'effet radiatif des nuages (CRE) dans un climat qui se réchauffe est incertaine. Afin de mieux comprendre l'évolution du CRE, il est utile de l'exprimer en fonction de propriétés nuageuses fondamentales et observables. Dans l'infrarouge (LW), l'altitude des nuages est une des propriétés fondamentales, ainsi que leur couverture et leur opacité. Les observations collectées par le lidar spatial CALIOP durant la dernière décennie nous ont permis d'exprimer le CRE LW en fonction de cinq propriétés nuageuses. Nous montrons que le CRE LW dépend linéairement de l'altitude des nuages. Cette linéarité permet de décomposer les variations du CRE LW en contributions dues aux cinq propriétés nuageuses. On observe ainsi que la couverture des nuages opaques a piloté les variations du CRE LW durant la dernière décennie. L'analyse de simulations climatiques suivant la même approche à l'aide d'un simulateur lidar montre que les variations du CRE LW dans le climat actuel sont pilotées par l'altitude des nuages opaques, en désaccord avec les observations. Lorsqu'on étend cette analyse aux rétroactions nuageuses LW simulées dans un climat futur, on remarque que celles-ci sont également pilotées par l'altitude des nuages opaques. Ces résultats suggèrent que les observations par lidar spatial apportent une forte contrainte observationnelle sur les rétroactions nuageuses LW, qui sont l'une des principales sources d'incertitude dans les prévisions d'évolution de la température moyenne globale dues aux activités humaines. / Because cloud processes are complex processes which operate at very different spatial scales, the evolution of the cloud radiative effect (CRE) in a warming climate is uncertain. To improve our understanding of the evolution of the CRE, it is useful to express it as a function of fundamental and observable cloud properties. In the infrared (LW), the altitude of clouds is one of the fundamental properties, together with their cover and opacity. The observations collected by the space-lidar CALIOP during the last decade allowed us to express the LW CRE using five cloud properties. We show that the LW CRE depends linearly on the cloud altitude. This linearity allows to decompose the variations of the LW CRE into contributions due to the five cloud properties. We observe that the cover of the opaque clouds drove the variations of the LW CRE during the last decade. The analysis of climate simulations performing the same approach by means of a lidar simulator shows that the variations of the LW CRE in the current climate are driven by the opaque cloud altitude, in disagreement with the observations. When we extend this analysis to the LW cloud feedback simulated in a future climate, we notice that they are also driven by the opaque cloud altitude. These results suggest that the space-lidar observations bring a strong observational constraint on the LW cloud feedbacks, which are one of the main sources of uncertainty in predicting future global average temperature evolution due to human activities.

Les systèmes de cartographie mobile sont de plus en plus utilisés pour la cartographie des scènes urbaines. La technologie de scan laser mobile (où le scanner est embarqué sur un véhicule) en particulier permet une cartographie précise de la voirie, la compréhension de la scène, la modélisation de façade, etc. Dans cette thèse, nous nous concentrons sur la détection de changement entre des nuages de points laser de cartographie mobile. Tout d'abord, nous étudions la détection des changements a partir de données RIEGL (scanner laser plan) pour la mise à jour de bases de données géographiques et l'identification d'objet temporaire. Nous présentons une méthode basée sur l'occupation de l'espace qui permet de surmonter les difficultés rencontrées par les méthodes classiques fondées sur la distance et qui ne sont pas robustes aux occultations et à l'échantillonnage anisotrope. Les zones occultées sont identifiées par la modélisation de l'état d'occupation de l'espace balayé par des faisceaux laser. Les écarts entre les points et les lignes de balayage sont interpolées en exploitant la géométrie du capteur dans laquelle la densité d'échantillonnage est isotrope. Malgré quelques limites dans le cas d'objets pénétrables comme des arbres ou des grilles, la méthode basée sur l'occupation est en mesure d'améliorer la méthode basée sur la distance point à triangle de façon significative. La méthode de détection de changement est ensuite appliquée à des données acquises par différents scanners laser et à différentes échelles temporelles afin de démontrer son large champs d'application. La géométrie d'acquisition est adaptée pour un scanner dynamique de type Velodyne. La méthode basée sur l'occupation permet alors la détection des objets en mouvement. Puisque la méthode détecte le changement en chaque point, les objets en mouvement sont détectés au niveau des points. Comme le scanner Velodyne scanne l'environnement de façon continue, les trajectoires des objets en mouvement peut être extraite. Un algorithme de détection et le suivi simultané est proposé afin de retrouver les trajectoires de piétons. Cela permet d'estimer avec précision la circulation des piétons des circulations douces dans les lieux publics. Les changements peuvent non seulement être détectés au niveau du point, mais aussi au niveau de l'objet. Ainsi nous avons pu étudier les changements entre des voitures stationnées dans les rues à différents moments de la journée afin d'en tirer des statistiques utiles aux gestionnaires du stationnement urbain. Dans ce cas, les voitures sont détectés en premier lieu, puis les voitures correspondantes sont comparées entre des passages à différents moments de la journée. Outre les changements de voitures, l'offre de stationnement et les types de voitures l'utilisant sont également des informations importantes pour la gestion du stationnement. Toutes ces informations sont extraites dans le cadre d'un apprentissage supervisé. En outre, une méthode de reconstruction de voiture sur la base d'un modèle déformable générique ajusté aux données est proposée afin de localiser précisément les voitures. Les paramètres du modèle sont également considérés comme caractéristiques de la voiture pour prendre de meilleures décisions. De plus, ces modèles géométriquement précis peuvent être utilisées à des fins de visualisation. Dans cette thèse, certains sujets liés à la détection des changements comme par exemple, suivi, la classification, et la modélisation sont étudiés et illustrés par des applications pratiques. Plus important encore, les méthodes de détection des changements sont appliquées à différentes géométries d'acquisition de données et à de multiples échelles temporelles et au travers de deux stratégies: “bottom-up” (en partant des points) et “top-down” (en partant des objets) / Mobile mapping systems are increasingly used for street environment mapping, especially mobile laser scanning technology enables precise street mapping, scene understanding, facade modelling, etc. In this research, the change detection from laser scanning point clouds is investigated. First of all, street environment change detection using RIEGL data is studied for the purpose of database updating and temporary object identification. An occupancy-based method is presented to overcome the challenges encountered by the conventional distance-based method, such as occlusion, anisotropic sampling. Occluded areas are identified by modelling the occupancy states within the laser scanning range. The gaps between points and scan lines are interpolated under the sensor reference framework, where the sampling density is isotropic. Even there are some conflicts on penetrable objects, e.g. trees, fences, the occupancy-based method is able to enhance the point-to-triangle distance-based method. The change detection method is also applied to data acquired by different laser scanners at different temporal-scales with the intention to have wider range of applications. The local sensor reference framework is adapted to Velodyne laser scanning geometry. The occupancy-based method is implemented to detection moving objects. Since the method detects the change of each point, moving objects are detect at point level. As the Velodyne scanner constantly scans the surroundings, the trajectories of moving objects can be detected. A simultaneous detection and tracking algorithm is proposed to recover the pedestrian trajectories in order to accurately estimate the traffic flow of pedestrian in public places. Changes can be detected not only at point level, but also at object level. The changes of cars parking on street sides at different times are detected to help regulate on-street car parking since the parking duration is limited. In this case, cars are detected in the first place, then they are compared with corresponding ones. Apart from car changes, parking positions and car types are also important information for parking management. All the processes are solved in a supervised learning framework. Furthermore, a model-based car reconstruction method is proposed to precisely locate cars. The model parameters are also treated as car features for better decision making. Moreover, the geometrically accurate models can be used for visualization purposes. Under the theme of change detection, related topics, e.g. tracking, classification, modelling, are also studied for the reason of practical applications. More importantly, the change detection methods are applied to different data acquisition geometries at multiple temporal-scales. Both bottom-up (point-based) and top-down (object-based) change detection strategies are investigated