Multi-level filtering segmentation to measure individual tree parameters based on Lidar data: Application to a mountainous forest with heterogeneous stands

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 the introduction of controls on both the degree of CSM filtering and the shape of elliptic crowns, in addition to a multi-filtering level crown fusion approach to balance omission and commission errors. The algorithm derives the total tree height and the mean crown diameter from the elliptic tree crowns generated. The method was tested and validated on a mountainous forested area mainly covered by mature and even-aged black pine (Pinus nigra ssp. nigra [Arn.]) stands. Mean stem detection per plot, using this method, was 73.97%. Algorithm performance was affected slightly by both stand density and heterogeneity (i.e. tree diameter classes' distribution). The total tree height and the mean crown diameter were estimated with root mean squared error values of 1.83 m and 1.48 m respectively. Tree heights were slightly underestimated in flat areas and overestimated on slopes. The average crown diameter was underestimated by 17.46% on average. (C) 2011 Elsevier B.V. All rights reserved

Revisiting the status of space-borne lidar missions for assessing structural and biophysical forest parameters in the context of sustainable management of Earth resources

International audienceAssessing forest aboveground biomass at global scale is crucial to address the challenge of sustainable management of forest resources and to strengthen forest-based climate change mitigation. To achieve this goal relying on spaceborne lidar missions is acknowledged to be a highly relevant solution. However, if this is taken as a given from the measurement point of view, the premise that spaceborne observation is the most suitable solution to provide information for sustainable management of forest resources is worth discussing. In this paper we suggest to take a fresh look at measurement processes designed to support the monitoring of Earth resources. We discuss the sustainability of Earth observation from space considering (1) issues that call into question the assumption that Earth-orbiting platform will always be available to the civilian remote sensing community and (2) issues concerning environmental impacts of space activity on the Earth. This leads us to suggest some actions that could help to design future observation systems in a more sustainable way in order to strengthen the capacity of measurement processes to meet their stated functional goal, i.e. sustainable management of forest resources

Apports de la technologie LIDAR dans l’objectivation écologique d’un territoire en amont d’un projet d’aménagement : aide à la caractérisation de l’habitat de l’Outarde canepetière dans la ZPS des Costières de Nîmes

International audienceDans le cadre du programme de recherche INTERMOPES1, des investigations ont été menées sur les technologies qui permettraient d’améliorer la caractérisation d’habitat d’espèces afin de développer des méthodes et outils d’objectivation écologiques du territoire. Le poster que nous proposons présentera les résultats d’une expérimentation réalisée avec un LIDAR terrestre dans le but d’analyser et de cartographier finement les hauteurs de végétation et de relier les informations acquises avec la présence de mâles ou de femelles d’Outardes canepetière. L’objectif de ces travaux est d’affiner les connaissances sur la répartition de l’oiseau dans le paysage de la Zone de Protection Spéciale des Costières de Nîmes (France) et de développer une méthode généralisable d’analyse instrumentée des potentialités écologiques d’un paysage

Improving the quantification of land cover pressure on stream ecological status at the riparian scale using High Spatial Resolution Imagery

The aim of this paper is to demonstrate the interest of High Spatial Resolution Imagery (HSRI) and the limits of coarse land cover data such as CORINE Land Cover (CLC), for the accurate characterization of land cover structure along river corridors and of its functional links with freshwater ecological status on a large scale. For this purpose, we compared several spatial indicators built from two land cover maps of the Herault river corridor (southern France): one derived from the CLC database, the other derived from HSRI. The HSRI-derived map was obtained using a supervised object-based classification of multi-source remotely-sensed images (SPOT 5 XS-10 m and aerial photography-0.5 m) and presents an overall accuracy of 70 %. The comparison between the two sets of spatial indicators highlights that the HSRI-derived map allows more accuracy in the quantification of land cover pressures near the stream: the spatial structure of the river landscape is finely resolved and the main attributes of riparian vegetation can be quantified in a reliable way. The next challenge will consist in developing an operational methodology using HSRI for large-scale mapping of river corridor land cover,, for spatial indicator computation and for the development of related pressure/impact models, in order to improve the prediction of stream ecological status

Mapping plant area index of tropical forest by Lidar: calibrating ALS with TLS

SilviLaser 2015, La Grande Motte, FRA, 28-/09/2015 - 30/09/2015International audienceHighlights: - We compare Plant Area Density (PAD) profiles derived from Terrestrial Laser Scanning (TLS) and contemporaneous Aerial Laser Scanning (ALS) in dense tropical forest- Poor sampling of the lower part of the canopy profile by ALS is mitigated by using a multiple resolution approach- Anisotropy of transmittance revealed by TLS allows further improvement of PAD estimates

Spatial quantification of vegetation density from terrestrial laser scanner data for characterization of 3D forest structure at plot level

International audiencePrecise 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 hypothesis that the normalized number of laser returns within a given volume element is proportional to the density of vegetation material inside this volume. The developed model is based on analysis made inside Svoxels (spherical voxels) to compute a spatialized vegetation density index. The model was tested on two different scans of the same plot. The resulting vegetation density index well represents the vegetation structure as observed within the lidar point cloud. Quantitative analyses confirmed a global consistency of the results within and between scans. However, we observed a slight bias in the computed density indexes. It might be mainly explained by occlusions, which cause 1) a slight decrease of the density index with distance and 2) local differences in density index between scans.. Future work will focus on improving our algorithm and correcting biases. These results are promising for the development of quantitative measures of the 3D forest structure

Détection de changements forestiers à l'aide d'images satellitales

La télédétection satellitale apparaît comme un outil performant d'analyse et de suivi des pratiques sylvicoles à l'échelle d'une région forestière ou d'un département

A method addressing signal occlusion by scene objects to quantify the 3D distribution of forest components from terrestrial lidar

SilviLaser 2015, La Grande Motte, FRA, 28-/09/2015 - 30/09/2015International audienceEstimating exact 3D distribution of canopy components using terrestrial lidar in forest is limited by signal occlusion. We propose a method to address this limitation: it uses voxels, beam returns and beam propagation through the scene. The proposed method was validated using simulated forest scenes and a lidar simulator

Low energy LIDARs for biomass applications

SilviLaser 2015, La Grande Motte, FRA, 28-/09/2015 - 30/09/2015International audienceA new approach for LIDAR altimetry mission for biomass applications ( tree height measurement ) is explored based on low emitted laser energy at high repetition fr equency. Low energy approach drastical ly reduces the laser induced risks. Altimetry performances meet preliminary science requirements . The proposed instrument design is compatible with a space mission

Modelling full waveform Lidar data on forest structures at plot level : a sensitivity analysis of forest and sensor main characteristics on full-waveform simulated data

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE [Axe_IRSTEA]TETIS-ATTOSSilviLaser, La Grande Motte, FRA, 28-/09/2015 - 30/09/2015International audienceA new approach for LIDAR altimetry mission for biomass applications (tree height measurement) is explored based on low emitted laser energy at high repetition frequency. Low energy approach drastical ly reduces the laser induced risks. Altimetry performances meet preliminary science requirements . The proposed instrument design is compatible with a space mission