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Dissertation
Structure d'une forêt claire de type miombo par imageries drone et satellitaire
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Year: 2019 Publisher: Liège Université de Liège (ULiège)

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Les écosystèmes forestiers d’Afrique sont en proie à la déforestation et subissent des dégradations, ayant pour conséquences une pression importante sur les services écosystémiques et une contribution à l’émission de gaz à effet de serre dans l’atmosphère. L’accessibilité et le faible coût des technologies liées à la télédétection en font des outils valorisables et prometteurs à la caractérisation de forêts claires de type miombos, première étape vers le suivi temporel des stocks de biomasse végétale et de carbone. L’objectif général de ce travail de fin d’étude est de caractériser la structure forestière d’un miombo en périphérie de la ville de Lubumbashi (RDC) à l’aide d’imageries drone et satellitaires. Une approche arbre au départ du Modèle Numérique de Hauteur de la zone d’étude de 10 hectares construit sur base des imageries acquises par drone a été mise en place, d’une part pour évaluer la performance de l’algorithme de détection des arbres individuels, et d’autre part pour valider les hauteurs extraites du Modèle Numérique de Hauteur en les comparant avec les mesures faites sur le terrain. L’identification des arbres individuels est jugée satisfaisante (score F = 0.76) de même que les hauteurs extraites du Modèle Numérique de Hauteur (R² = 0.835, RMSE% = 10.99%). Ensuite, une approche surface a permis de mettre en évidence un modèle d’estimation de la biomasse aérienne au départ du volume sous le Modèle Numérique de Hauteur volha et du coefficient de variation de la hauteur hcv (variables surfaciques extraites du Modèle Numérique de Hauteur) pour une taille de parcelle de 0.25 ha (R² aj = 0.65, RMSE% = 14.43%). Finalement, un test de corrélation linéaire de Pearson a été fait entre la biomasse aérienne et, d’un côté, cinq indices de végétation calculés au départ des bandes spectrales des imageries Sentinel-2 et, d’un autre côté, l’intensité de rétrodiffusion en polarisations VV et VH d’imageries Sentinel-1. Les hautes valeurs de biomasse aérienne ainsi que leur faibles gammes n’ont pas permis de mettre en évidence une relation linéaire probante. De ce fait, aucun modèle d’estimation de la biomasse aérienne au départ d’imageries satellitaires n’a été construit. Les outils de télédétection appliqués aux miombos humides sont prometteurs au vu des résultats obtenus, ayant néanmoins permis de mettre en évidence l’importance d’un échantillonnage adéquat. Il est dès lors recommandé de combiner les technologies satellitaires, d’étendre la gamme de biomasse aérienne et d’augmenter le nombre de parcelles afin d’optimiser la représentativité de l’échantillonnage et de pouvoir construire des modèles d’estimation de la biomasse aérienne valides. Africa’s forest ecosystems are suffering from deforestation and degradation, resulting in significant pressure on ecosystem services and a contribution to the emission of greenhouse gases into the atmosphere. The accessibility and low cost of remote sensing technologies make them valuable and promising tools for characterizing miombo woodlands, a first step towards temporal monitoring of plant biomass and carbon stocks. The general objective of this master thesis is to characterize the forest structure of a miombo on the outskirts of Lubumbashi (DRC) using UAV and satellite imagery. A tree-based approach based on the Canopy Height Model of the 10 hectares study area derived from UAV images was implemented, on the one hand to evaluate the performance of the algorithm for detecting individual trees, and on the other hand to validate the heights extracted from the Canopy Height Model by comparing them with the measurements made in the field. The identification of individual trees is considered satisfactory (score F = 0.76) as well as the heights extracted from the Canopy Height Model (R² = 0.835, RMSE% = 10.99%). Then, an area-based approach made possible the development of a model for estimating above-ground biomass from the volume under the Canopy Height Model volha and the coefficient of variation of height hcv (metrics derived from the Canopy Height Model) for a plot size of 0.25 ha (R² adj = 0.65, RMSE% = 14.43%). Finally, a Pearson linear correlation test was performed between the above-ground biomass and, on the one hand, five vegetation indices computed from the spectral bands of Sentinel-2 imageries and, on the other hand, the backscatter intensity in VV and VH polarizations of Sentinel-1 imageries. The high values of above-ground biomass and their low ranges did not reveal a convincing linear relationship. As a result, no model for estimating above-ground biomass from satellite imagery has been developed. Remote sensing tools applied to wet miombos are promising in view of the results obtained, but have nevertheless highlighted the importance of adequate sampling. It is therefore recommended to combine satellite technologies, extend the range of above-ground biomass and
increase the number of plots in order to optimise the representativeness of the sampling and to be able to build valid above-ground biomass estimation models.


Book
Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass
Author:
Year: 2021 Publisher: Basel, Switzerland MDPI - Multidisciplinary Digital Publishing Institute

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This Special Issue (SI), entitled "Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass”, resulted from 13 peer-reviewed papers dedicated to Forestry and Biomass mapping, characterization and accounting. The papers' authors presented improvements in Remote Sensing processing techniques on satellite images, drone-acquired images and LiDAR images, both aerial and terrestrial. Regarding the images’ classification models, all authors presented supervised methods, such as Random Forest, complemented by GIS routines and biophysical variables measured on the field, which were properly georeferenced. The achieved results enable the statement that remote imagery could be successfully used as a data source for regression analysis and formulation and, in this way, used in forestry actions such as canopy structure analysis and mapping, or to estimate biomass. This collection of papers, presented in the form of a book, brings together 13 articles covering various forest issues and issues in forest biomass calculation, constituting an important work manual for those who use mixed GIS and RS techniques.


Book
Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass
Author:
Year: 2021 Publisher: Basel, Switzerland MDPI - Multidisciplinary Digital Publishing Institute

Loading...
Export citation

Choose an application

Bookmark

Abstract

This Special Issue (SI), entitled "Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass”, resulted from 13 peer-reviewed papers dedicated to Forestry and Biomass mapping, characterization and accounting. The papers' authors presented improvements in Remote Sensing processing techniques on satellite images, drone-acquired images and LiDAR images, both aerial and terrestrial. Regarding the images’ classification models, all authors presented supervised methods, such as Random Forest, complemented by GIS routines and biophysical variables measured on the field, which were properly georeferenced. The achieved results enable the statement that remote imagery could be successfully used as a data source for regression analysis and formulation and, in this way, used in forestry actions such as canopy structure analysis and mapping, or to estimate biomass. This collection of papers, presented in the form of a book, brings together 13 articles covering various forest issues and issues in forest biomass calculation, constituting an important work manual for those who use mixed GIS and RS techniques.


Book
Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass
Author:
Year: 2021 Publisher: Basel, Switzerland MDPI - Multidisciplinary Digital Publishing Institute

Loading...
Export citation

Choose an application

Bookmark

Abstract

This Special Issue (SI), entitled "Applications of Remote Sensing Data in Mapping of Forest Growing Stock and Biomass”, resulted from 13 peer-reviewed papers dedicated to Forestry and Biomass mapping, characterization and accounting. The papers' authors presented improvements in Remote Sensing processing techniques on satellite images, drone-acquired images and LiDAR images, both aerial and terrestrial. Regarding the images’ classification models, all authors presented supervised methods, such as Random Forest, complemented by GIS routines and biophysical variables measured on the field, which were properly georeferenced. The achieved results enable the statement that remote imagery could be successfully used as a data source for regression analysis and formulation and, in this way, used in forestry actions such as canopy structure analysis and mapping, or to estimate biomass. This collection of papers, presented in the form of a book, brings together 13 articles covering various forest issues and issues in forest biomass calculation, constituting an important work manual for those who use mixed GIS and RS techniques.

Keywords

Research & information: general --- Geography --- AGB estimation and mapping --- mangroves --- UAV LiDAR --- WorldView-2 --- terrestrial laser scanning --- above-ground biomass --- nondestructive method --- DBH --- bark roughness --- Landsat dataset --- forest AGC estimation --- random forest --- spatiotemporal evolution --- aboveground biomass --- variable selection --- forest type --- machine learning --- subtropical forests --- Landsat 8 OLI --- seasonal images --- stepwise regression --- map quality --- subtropical forest --- urban vegetation --- biomass estimation --- Sentinel-2A --- Xuzhou --- forest biomass estimation --- forest inventory data --- multisource remote sensing --- biomass density --- ecosystem services --- trade-off --- synergy --- multiple ES interactions --- valley basin --- norway spruce --- LiDAR --- allometric equation --- individual tree detection --- tree height --- diameter at breast height --- GEOMON --- ALOS-2 L band SAR --- Sentinel-1 C band SAR --- Sentinel-2 MSI --- ALOS DSM --- stand volume --- support vector machine for regression --- ordinary kriging --- forest succession --- leaf area index --- plant area index --- machine learning algorithms --- forest growing stock volume --- SPOT6 imagery --- Pinus massoniana plantations --- sentinel 2 --- landsat --- remote sensing --- GIS --- shrubs biomass --- bioenergy --- vegetation indices --- AGB estimation and mapping --- mangroves --- UAV LiDAR --- WorldView-2 --- terrestrial laser scanning --- above-ground biomass --- nondestructive method --- DBH --- bark roughness --- Landsat dataset --- forest AGC estimation --- random forest --- spatiotemporal evolution --- aboveground biomass --- variable selection --- forest type --- machine learning --- subtropical forests --- Landsat 8 OLI --- seasonal images --- stepwise regression --- map quality --- subtropical forest --- urban vegetation --- biomass estimation --- Sentinel-2A --- Xuzhou --- forest biomass estimation --- forest inventory data --- multisource remote sensing --- biomass density --- ecosystem services --- trade-off --- synergy --- multiple ES interactions --- valley basin --- norway spruce --- LiDAR --- allometric equation --- individual tree detection --- tree height --- diameter at breast height --- GEOMON --- ALOS-2 L band SAR --- Sentinel-1 C band SAR --- Sentinel-2 MSI --- ALOS DSM --- stand volume --- support vector machine for regression --- ordinary kriging --- forest succession --- leaf area index --- plant area index --- machine learning algorithms --- forest growing stock volume --- SPOT6 imagery --- Pinus massoniana plantations --- sentinel 2 --- landsat --- remote sensing --- GIS --- shrubs biomass --- bioenergy --- vegetation indices

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