Cedric Vega

National Institute of Geographic and Forest Information · Laboratory of Forest Inventory

Remote sensing data are increasingly available and frequently used to produce forest attributes maps. The sampling strategy of the calibration plots may directly affect predictions and map qualities. The aim of this manuscript is to evaluate models transferability at different spatial scales according to the sampling efforts and the calibration dom...

Purpose of the Review Many LiDAR remote sensing studies over the past decade promised data fusion as a potential avenue to increase accuracy, spatial-temporal resolution, and information extraction in the final data products. Here, we performed a structured literature review to analyze relevant studies on these topics published in the last decade a...

The development of high-resolution mapping models for forest attributes based on remote sensing data combined with machine or deep learning techniques, has become a prominent topic in the field of forest observation and monitoring. This has resulted in an extensive availability of multiple sources of information, which can either lead to a potentia...

The Global Ecosystem Dynamics Investigation (GEDI) mission can significantly enhance Multi-Source National Forest Inventories (MSNFI) by improving the spatio-temporal resolution of forest attributes while preserving the statistical relevance of the design-based inference approach. The main challenge is the lack of systematic spatial alignment betwe...

The contribution of forests to carbon storage and biodiversity conservation highlights the need for accurate forest height and biomass mapping and monitoring. In France, forests are managed mainly by private owners and divided into small stands, requiring 10 to 50 m spatial resolution data to be correctly separated. Further, 35 % of the French fore...

The contribution of forests to carbon storage and biodiversity conservation highlights the need for accurate forest height and biomass mapping and monitoring. In France, forests are managed mainly by private owners and divided into small stands, requiring 10 to 50 m spatial resolution data to be correctly separated. Further, 35 % of the French fore...

p>GEDI (Global Ecosystem Dynamics Investigation) is a lidar system on-board the International Space Station designed to study forest ecosystems. However, GEDI footprint low accuracy geolocation is a major impediment to the optimal benefit of the data. We thus proposed a geolocation correction method, GeoGEDI, only based on high-resolution digital t...

p>GEDI (Global Ecosystem Dynamics Investigation) is a lidar system on-board the International Space Station designed to study forest ecosystems. However, GEDI footprint low accuracy geolocation is a major impediment to the optimal benefit of the data. We thus proposed a geolocation correction method, GeoGEDI, only based on high-resolution digital t...

GEDI (Global Ecosystem Dynamics Investigation) is a lidar system on-board the International Space Station designed to study forest ecosystems. However, GEDI footprint low accuracy geolocation is a major impediment to the optimal benefit of the data. We thus proposed a geolocation correction method, GeoGEDI, only based on high-resolution digital ele...

In intensively managed forests in Europe, where forests are divided into stands of small size and may show heterogeneity within stands, a high spatial resolution (10 - 20 meters) is arguably needed to capture the differences in canopy height. In this work, we developed a deep learning model based on multi-stream remote sensing measurements to creat...

Key message Forest monitoring in Europe is turning matter of renewed political concern, and a possible role for ICP Forests health monitoring has been suggested to meet this goal (Ann For Sci 78:94, 2021). Multipurpose national forest inventory (NFI) surveys yet offer a sampling effort by two orders of magnitude greater than ICP level 1, have accom...

The French National Forest Inventory provides detailed forest information up to large national and regional scales. Forest inventory for small areas of interest within a large population is equally important for decision making, such as for local forest planning and management purposes. However, sampling these small areas with sufficient ground plo...

Forest map products are widely used and have taken benefit from progresses in the multisource forest inventory approaches, which are meant to improve the precision of forest inventory estimates at high spatial resolution. However, estimating errors of pixel-wise predictions remains difficult, and reconciling statistical outcomes with map products i...

A R T I C L E I N F O Keywords: Calibration domain Model-based maps Model transferability Extrapolation bias Airborne laser scanning Sampling effort A B S T R A C T The ever-increasing availability of remote sensing data allows production of forest attributes maps, which are usually made using model-based approaches. These map products are sensitiv...

Combining national forest inventory (NFI) data with auxiliary information allows downscaling and improving the precision of NFI estimates for small domains, where normally too few field plots are available to produce reliable estimates. In most situations, small domains represent administrative units that could greatly vary in size and forested are...

Terrestrial laser scanners provide accurate and detailed point clouds of forest plots, which can be used as an alternative to destructive measurements during forest inventories. Various specialized algorithms have been developed to provide automatic and objective estimates of forest attributes from point clouds. The STEP (Snakes for Tuboid Extracti...

Key message : The accuracy of remote sensing-based models of forest attributes could be improved by controlling the spatial registration of field and remote sensing data. We have demonstrated the potential of an algorithm matching plot-level field tree positions with lidar canopy height models and derived local maxima to achieve a precise registra...

The diversification of wood usages and the information needs for international reporting require detailed information on total tree volume and biomass. National Forest Inventories have traditionally estimated merchantable volume based on diameter and height measures and allometric models, but they need to get new efficient ways to estimate of total...

International reporting and societal demand require information on total wood volume and biomass. National Forest Inventories collect most of the time information on the main stem. Volume and biomass equations exist to estimate totals from the stem. However, they are most often based on small databases that do not represent all the forest condition...

Multisource forest inventory methods were developed to improve the precision of national forest inventory estimates. These methods rely on the combination of inventory data and auxiliary information correlated with forest attributes of interest. As these methods have been predominantly tested over coniferous forests, the present study used this app...

This paper introduces a novel surface reconstruction method based on unorganized point clouds, which focuses on offering complete and closed mesh models of partially sampled object surfaces. To accomplish this task, our approach builds upon a known a priori model that coarsely describes the scanned object to guide the modeling of the shape based on...

Key message: Diachronic photogrammetric canopy height models can be used to quantify at a fine scale changes in dominant height and wood volume following storms. The regular renewal of aerial surveys makes this approach appealing for monitoring forest changes. Context: The increasing availability of aerial photographs and the development of dense m...

The presence of vegetation and the terrain topography itself generate strong occlusions causing large gaps in terrestrial laser scanning (TLS) data at the ground level as well as a risk of integrating above-ground objects. This article introduces a surface-approximation algorithm dedicated to extracting digital terrain models (DTMs) from terrestria...

Les forêts, regardées ici comme des ressources, vont se transformer au cours des prochaines décennies, à la fois passivement et de manière programmée, sous l’effet conjugué du changement climatique et de l’évolution des pratiques de gestion. L’objectif de cette communication, réalisée à la demande de l’IGN, est de situer le rôle que doit et va joue...

article présenté lors du Colloque CIAg "Une bioéconomie basée sur la forêt et le bois ?" organisé à Nancy le 8 décembre 2016.

Résumé Une bioéconomie fondée sur la forêt et le bois implique de concevoir de nouvelles stratégies de gestion pour simultanément adapter la forêt au changement climatique et lui permettre de répondre aux demandes accrues en visant l’optimisation d’un bilan carbone forêt-bois intégré. Par rapport aux inventaires forestiers tels qu’ils existent aujo...

We proposed a new area-based approach to process Lidar point clouds and develop new sets of metrics to improve models dedicated to predict forest parameters. First, we introduced point normalization based on penetration depth below the outer canopy layer to avoid biases introduced by ground normalization and canopy surface heterogeneity during metr...

Optical remote sensing of tree and stand heights

We developed an-object based framework to assess individual tree volume from airborne LiDAR data in a pine-dominated forest. Individual tree crowns were extracted using a point-based segmentation algorithm and total tree volume was estimated using height and either tree or crown bounding volume information using nonlinear models. Tree-level models...

Our forest information needs are growing with high requirements in terms of accuracy, spatial resolution and costs. Thus, forest inventories innovation is a constantly evolving field. In this study, we evaluated the contribution of digital height models (DHM) as auxiliary data to improve the accuracy of inventory estimates. Two study areas were sel...

Recent developments in the field of airborne laser scanning offer new possibilities to map different forest attributes and improve forest Inventory accuracy. In this work, two methods of LiDAR point clouds segmentation were used to obtain new variables and assess the gain in accuracy to estimate dominant height, basal area and volume, in three cont...

Most volume estimation methods consider the tree as a set of perfect cylinders, which is far from being true and might lead to substantial errors. We base our method on a Modified Hough Transform Approach (MHTA) to detect and segment individual trees. To estimate the volume, the method uses cylindrical quadrics patches and compactly supported radia...

Light Detection and Ranging (Lidar) is a state of the art technology to assess forest aboveground biomass (AGB). To date, methods developed to relate Lidar metrics with forest parameters were built upon the vertical component of the data. In multi-layered tropical forests, signal penetration might be restricted, limiting the efficiency of these met...

Light Detection and Ranging (Lidar) is a state of the art technology to assess forest aboveground biomass (AGB). To date, methods developed to relate Lidar metrics with forest parameters were built upon the vertical component of the data. In multi-layered tropical forests, signal penetration might be restricted, limiting the efficiency of these met...

This paper introduces PTrees, a multi-scale dynamic point cloud segmentation dedicated to forest tree extraction from lidar point clouds. The method process the point data using the raw elevation values (Z) and compute height (H = Z − ground elevation) during post-processing using an innovative procedure allowing to preserve the geometry of crown p...

Field data describing the height growth of trees or stands over several decades are very scarce. Consequently, our capacity of analyzing forest dynamics over large areas and long periods of time is somewhat limited. This study proposes a new method for retrospectively reconstructing plot-wise average dominant tree height based on a time series of h...

The diameter at breast height (DBH) is the most extensively measured parameter in the field for estimating stem volume and aboveground biomass of individual trees. However, DBH can not be measured from airborne or spaceborne light detection and ranging (LiDAR) data. Consequently, volume and biomass must be estimated from LiDAR data using other tree...

This paper introduces a sequential iterative dual-filter method for filtering Lidar point clouds acquired over rough and forested terrain and computing a digital terrain model (DTM). The method belongs to the family of virtual deforestation algorithms that iteratively detect and filter objects above-the ground surface. The method uses both points a...

The aim of the paper is to carry on methodological development for retrievingforest parameters from medium-footprintlidar signals and for assessing the performance of different sampling strategies. The 2.4 m footprintlidarprototype (a profiler instrument using an ultraviolet laser) was flown above two different maritime pine stands: a young planta...

This paper presents a method for individual tree crown extraction and characterisation from a canopy surface model (CSM). The method is based on a conventional algorithm used for localising LM on a smoothed version of the CSM and subsequently for modelling the tree crowns around each maximum at the plot level. The novelty of the approach lies in th...

Volume and biomass are estimated mostly using tree diameter at breast height (BDH), which is not reachable using light detection and ranging (lidar) data. In this paper, we compare volume and biomass estimations performed using lidar metrics derived from a traditional canopy height model (CHM), such as total height and crown area, with estimations...

Quantifying and monitoring the structure and degradation of tropical forests over regional to global scales is gaining increasing scientific and societal importance. Reliable automated methods are only beginning to appear; for instance, through the recent development of textural approaches applied to high resolution optical imagery. In particular,...

Reliable and very height spatial resolution data on forest structure are necessary to elaborate silvicultural guide and to optimize silvicultural strategies. Airborne laser scanning data allows to extract 3D information from individual trees growing within forest stands. Such dense information information, including tree positions, height of the ap...

Small footprint full-waveform airborne lidar systems hold large opportunities for improved forest characterisation. To take advantage of full-waveform information, this paper presents a new processing method based on the decomposition of waveforms into a sum of parametric functions. The method consists of an enhanced peak detection algorithm combin...

Small footprint full-waveform airborne lidar systems offer large opportunities for improved forest characterization. To take advantage of full-waveform information, this paper presents a new processing method based on the decomposition of waveforms into a sum of parametric functions. The method consists of an enhanced peak detection algorithm combi...

Site index (SI) is one of the main measures of forest productivity in North America. For monospecific even-age stands, it is defined as the height of dominant trees at a given reference age or presented as an age–height curve. SI normally reflects the overall effect of all the environmental parameters that determine height growth locally. However,...

Precise description of forest 3D structure at plot level is required for sustainable ecosystem management. However, a detailed structure description from traditional field measurements is tedious. We propose an innovative method to quantify in 3D the spatial distribution of forest structure from terrestrial lidar data. The method rests on the hypot...

Ranging techniques such as lidar (LIght Detection And Ranging) and digital stereo‐photogrammetry show great promise for mapping forest canopy height. In this study, we combine these techniques to create hybrid photo‐lidar canopy height models (CHMs). First, photogrammetric digital surface models (DSMs) created using automated stereo‐matching were r...

Our objective was to assess the accuracy of the forest height and biomass estimates derived from an Ikonos stereo pair and a lidar digital terrain model (DTM). After the Ikonos scenes were registered to the DTM with submetric accuracy, tree heights were measured individually by subtracting the photogrammetric elevation of the treetop from the lidar...

Ranging techniques such as lidar (LIght Detection And Ranging) and digital stereo‐photogrammetry show great promise for mapping forest canopy height. In this study, we combine these techniques to create hybrid photo‐lidar canopy height models (CHMs). First, photogrammetric digital surface models (DSMs) created using automated stereo‐matching were r...

Our objective was to assess the accuracy of the forest height and biomass estimates derived from an Ikonos stereo pair and a lidar digital terrain model (DTM). After the Ikonos scenes were registered to the DTM with submetric accuracy, tree heights were measured individually by subtracting the photogrammetric elevation of the treetop from the lidar...

La mesure précise de la structure verticale des canopées, à haute résolution spatiotemporelle, est une composante essentielle de l’étude de la dynamique forestière. Traditionnellement, les mesures de hauteur et de croissance impliquent des inventaires ponctuels de terrain à l’échelle de la placette, qui sont coûteuses et représentent mal l’organisa...

The objective of this study was to assess the accuracy of 1) individual tree height measurements and 2) automated mapping of canopy height based on a combination of an Ikonos stereo-model and a lidar DTM. The Ikonos stereo-model was registered to the lidar DTM with sub-meter accuracy. The height of 99 trees was measured manually by subtracting the...

Estimation of forest height and growth is based on repeated measurements of site-specific biophysical characteristics. Conventional assessment is made on field measurements which are uneconomical and inaccurate. Moreover, height estimation remains a difficult task. Several studies have shown that precise height metrics can be derived through surfac...

Photogrammetric methods using parallaxes can be employed to measure tree heights on aerial photographs. Because it is often impossible to measure ground elevation near trees growing in dense forests, such height measurements remain prone to error. Our objective was to solve this problem by combining a stereomodel and a digital terrain model (DTM) p...

The mobile mud banks, several kilometres wide and about 30 km long, which form the sedimentary environment of the coast of the Guianas are a consequence of the huge particulate discharge of the Amazon. These mud banks shift towards the northwest, influenced by the combined action of accretion and erosion, a process also affected by periodic variabi...

The mobile mud banks, several kilometres wide and about 30 km long, which form the sedimentary environment of the coast of the Guianas are a consequence of the huge particulate discharge of the Amazon. These mud banks shift towards the northwest, influenced by the combined action of accretion and erosion, a process also affected by periodic variabi...

Lidar and digital stereo-photogrammetry techniques are being developed to improve on current methods used to map forest canopy height. Contrary to lidar, the latter technique is limited in that is does not have the capacity to automatically produce dense and accurate information on the ground elevations needed to calculate height. We propose a new...

Les changements climatiques actuels se caractérisent pour les zones boréales par un réchauffement moyen de 0,6°C, et une augmentation substantielle des précipitations. Cette élévation des températures liée à l’augmentation des gaz à effet de serre (GES) est responsable de modifications dans la structure et la fonction des forêts boréales. Cela dit,...