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

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

Biomass prediction in tropical forests : the canopy grain approach

18 pagesThe challenging task of biomass prediction in dense and heterogeneous tropical forest requires a multi-parameter and multi-scale characterization of forest canopies. Completely different forest structures may indeed present similar above ground biomass (AGB) values. This is probably one of the reasons explaining why tropical AGB still resists accurate mapping through remote sensing techniques. There is a clear need to combine optical and radar remote sensing to benefit from their complementary responses to forest characteristics. Radar and Lidar signals are rightly considered to provide adequate measurements of forest structure because of their capability of penetrating and interacting with all the vegetation strata. However, signal saturation at the lowest radar frequencies is observed at the midlevel of biomass range in tropical forests (Mougin et al. 1999; Imhoff, 1995). Polarimetric Interferometric (PolInsar) data could improve the inversion algorithm by injecting forest interferometric height into the inversion of P-band HV polarization signal. Within this framework, the TROPISAR mission, supported by the Centre National d'Etudes Spatiales (CNES) for the preparation of the European Space Agency (ESA) BIOMASS program is illustrative of both the importance of interdisciplinary research associating forest ecologists and physicists and the importance of combined measurements of forest properties. Lidar data is a useful technique to characterize the vertical profile of the vegetation cover (e.g. Zhao et al. 2009) which in combination with radar (Englhart et al. 2011) or optical (e.g. Baccini et al. 2008; Asner et al. 2011) and field plot data may allow vegetation carbon stocks to be mapped over large areas of tropical forest at different resolution scales ranging from 1 hectare to 1 km². However, small-footprint Lidar data are not yet accessible over sufficient extents and with sufficient revisiting time because its operational use for tropical studies remains expensive. At the opposite, very-high (VHR) resolution imagery, i.e. approximately 1-m resolution, provided by recent satellite like Geoeye, Ikonos, Orbview or Quickbird as well as the forthcoming Pleiades becomes widely available at affordable costs, or even for free in certain regions of the world through Google Earth®. Compared to coarser resolution imagery with pixel size greater than 4 meters, VHR imagery greatly improves thematic information on forest canopies. Indeed, the contrast between sunlit and shadowed trees crowns as visible on such images (Fig. 1) is potentially informative on the structure of the forest canopy while new promising methods now exist for analyzing these fine scale satellite observations (e.g. Bruniquel-Pinel & Gastellu-Etchegorry, 1998; Malhi & Roman-Cuesta, 2008; Rich et al. 2010). Besides, we believe that there is also a great potential in similarly using historical series of digitized aerial photographs that proved to be useful in the past for mapping large extents of unexplored forest (Le Touzey, 1968; Richards, 1996) for quantifying AGB changes through time. This book chapter presents the advancement of a research program undertaken by our team for estimating high biomass mangrove and terra firme forests of Amazonia using canopy grain from VHR images (Couteron et al. 2005; Proisy et al. 2007; Barbier et al., 2010; 2011). We present in a first section, the canopy grain notion and the fundamentals of the Fourier-based Textural Ordination (FOTO) method we developed. We then introduce a dual experimental-theoretical approach implemented to understand how canopy structure modifies the reflectance signal and produces a given texture. We discuss, for example, the influence of varying sun-view acquisition conditions on canopy grain characteristics. A second section assesses the potential and limits of the canopy grain approach to predict forest stand structure and more specifically above ground biomass. Perspectives for a better understanding of canopy grain-AGB relationships conclude this work

Discrete anisotropic radiative transfer (DART 5) for modeling airborne and satellite spectroradiometer and LIDAR acquisitions of natural and urban landscapes

International audienceSatellite and airborne optical sensors are increasingly used by scientists, and policy makers, and managers for studying and managing forests, agriculture crops, and urban areas. Their data acquired with given instrumental specifications (spectral resolution, viewing direction, sensor field-of-view, etc.) and for a specific experimental configuration (surface and atmosphere conditions, sun direction, etc.) are commonly translated into qualitative and quantitative Earth surface parameters. However, atmosphere properties and Earth surface 3D architecture often confound their interpretation. Radiative transfer models capable of simulating the Earth and atmosphere complexity are, therefore, ideal tools for linking remotely sensed data to the surface parameters. Still, many existing models are oversimplifying the Earth-atmosphere system interactions and their parameterization of sensor specifications is often neglected or poorly considered. The Discrete Anisotropic Radiative Transfer (DART) model is one of the most comprehensive physically based 3D models simulating the Earth-atmosphere radiation interaction from visible to thermal infrared wavelengths. It has been developed since 1992. It models optical signals at the entrance of imaging radiometers and laser scanners on board of satellites and airplanes, as well as the 3D radiative budget, of urban and natural landscapes for any experimental configuration and instrumental specification. It is freely distributed for research and teaching activities. This paper presents DART physical bases and its latest functionality for simulating imaging spectroscopy of natural and urban landscapes with atmosphere, including the perspective projection of airborne acquisitions and LIght Detection And Ranging (LIDAR) waveform and photon counting signals

Eina per a la captació de talent al grau d'enginyeria química (#TEQxC2): el cas de la UPC Manresa

L'ocupabilitat és un dels atractius que aporten valor als estudis de grau de les enginyeries. En aquest sentit la UPC de Manresa dinamitza la captació d'estudiants en el grau d'enginyeria química a partir del programa talent en l'enginyeria química per a la Catalunya central, en el qual s'ofereix com a ingredient singular l'experiència d'enginyers que treballen en la indústria com a vincle per captar l'interès dels estudiants de batxillerat a partir de la selecció dels professors de batxillerat. Employability is one of the attractions that add value to undergraduate engineering degree studies. In this sense, the UPC of Manresa dynamizes the recruitment of students in the degree of chemical engineering from the talent program in chemical engineering for Central Catalonia, (TECxC2) which offers as an outstanding ingredient the experience of engineers who work in industry as a link to attract the interest of high school students from the selection made by their own teachers.Peer ReviewedPostprint (published version

The fourth phase of the radiative transfer model intercomparison (RAMI) exercise : Actual canopy scenarios and conformity testing

The RAdiative transfer Model Intercomparison (RAMI) activity focuses on the benchmarking of canopy radiative transfer (RT) models. For the current fourth phase of RAMI, six highly realistic virtual plant environments were constructed on the basis of intensive field data collected from (both deciduous and coniferous) forest stands as well as test sites in Europe and South Africa. Twelve RT modelling groups provided simulations of canopy scale (directional and hemispherically integrated) radiative quantities, as well as a series of binary hemispherical photographs acquired from different locations within the virtual canopies. The simulation results showed much greater variance than those recently analysed for the abstract canopy scenarios of RAMI-IV. Canopy complexity is among the most likely drivers behind operator induced errors that gave rise to the discrepancies. Conformity testing was introduced to separate the simulation results into acceptable and non-acceptable contributions. More specifically, a shared risk approach is used to evaluate the compliance of RI model simulations on the basis of reference data generated with the weighted ensemble averaging technique from ISO-13528. However, using concepts from legal metrology, the uncertainty of this reference solution will be shown to prevent a confident assessment of model performance with respect to the selected tolerance intervals. As an alternative, guarded risk decision rules will be presented to account explicitly for the uncertainty associated with the reference and candidate methods. Both guarded acceptance and guarded rejection approaches are used to make confident statements about the acceptance and/or rejection of RT model simulations with respect to the predefined tolerance intervals. (C) 2015 The Authors. Published by Elsevier Inc.Peer reviewe

Jornada "Experiències d'Aprenentatge Servei a la Universitat de Barcelona". Desenvolupament i experiències presentades.

La Jornada, titulada “Experiències d’Aprenentatge Servei a la Universitat de Barcelona”, te la finalitat de facilitar una reflexió conjunta sobre l’aplicació de l’ApS a la tasca docent i compartir les experiències desenvolupades a la nostra universitat. L'infome presenta el desenvolupament de la jornada i el recull dels pòsters presentats pels participants.ICE-IDP, Grup ApS (UB

Modélisation DART du transfert radiatif Terre-Atmosphère pour simuler les bilans radiatif, images de télédétection et mesures LIDAR des paysages terrestres

Emission and propagation of light in Earth Landscapes (i.e. Radiative Transfer) constricts the functioning of the biosphere on one hand, and the remote sensing data (satellite imagery, lidar signals). The measured signals depend on many factors, both experimentals and instrumentals. The RT modeling links remote sensing data to biophysical variables that characterize the landscape, in order to refine the data analysis or to assist in the technical specification of future sensors. This thesis presents the Discrete Anisotropic Radiative Transfer (DART) model and its recent improvements. This model represents the 3-dimensional landscapes in a matrix of cells, with consideration of the atmosphere. Vegetation, which is the main study, can be represented by a 1D, 2D or detailed 3D description using triangles, or by a classical statistical approach. Improvements of the model I made are of different types : improvement of the RT in the atmosphere, implementation of LIDAR modeling with a Monte Carlo approach and implementation of an original approach to model vegetation covers with varying degrees of realism. In addition to these theoretical works, I have strongly contributed to improve the code, with in particular transformation to a C++ code, making DART more robust, efficient, and easy to use to study earth surfaces by remote sensing.L'émission et la propagation de la lumière dans les paysages terrestres (i.e. le Transfert Radiatif (TR)) conditionne leur fonctionnement et leur observation par télédétection satellite (radiomètres, Lidar). Les signaux mesurés dépendent de multiples facteurs, à la fois et. La modélisation du TR est potentiellement l'outil idéal pour relier les mesures de télédétection à certaines caractéristiques biophysiques (occupation du sol, biomasse, etc.) des paysages observés, afin d'étudier les surfaces terrestres à partir de mesures satellites, mais aussi pour la préparation des futures missions spatiales dédiées à l'observation de la Terre. Cette thèse présente le modèle Discrete Anisotropic Radiative Transfer (DART) et les améliorations récentes apportées. Ce modèle simule la propagation du rayonnement dans le système "Terre - Atmosphère" à partir de la méthode de suivi de flux ou de la méthode de suivi de photons selon un nombre fini de directions discrètes dans un paysage 3D. Les améliorations que j'ai apportées au modèle DART sont de différents types : j'ai fortement amélioré la modélisation du TR dans l'atmosphère, j'ai introduit la modélisation Lidar à partir d'une modélisation Monte-Carlo pré-existante et j'ai introduit une approche pour modéliser les couverts végétaux avec différents degrés de réalisme. En plus de ces travaux théoriques, j'ai aussi fortement contribué à l'amélioration du code, avec en particulier le passage de code en C++. Finalement, DART est devenu un modèle plus performant et donc plus efficace pour l'étude des surfaces terrestres par télédétection

Etude de sensibilité du signal Lidar - Validation de la modélisation

This work presents and compares several approaches of Lidar signal modelling on forested environment. Different types of forest scenes, more or less realistic, are simulated from field surveys. A new approach to produce realistic forest scenes is introduced and validated. It consists in representing the forest scenes from terrestrial lidar (TLS) data acquired in the field. TLS data are voxellised and a plant area density is computed for each voxel, thus enabling a detailed representation of the 3D structure of the vegetation. Signals acquired by an airborne Lidar are then simulated by radiative transfer using DART,a model developed by Cesbio. In order to validate the simulation approaches, the signals obtained by simulation are compared with experimental airborne lidar data, when available. However, the validation remains relative, as the radiometric calibration of the airborne Lidar system could not be finalized at this stage. A sensitivity analysis of the simulated signal to different environmental and system parameters is then carried out in order to understand the impact of these parameters on the quality of the signal. From these analyzes, preliminary recommendations for the design of a vegetation space Lidar system can be deduced.Ce travail présente et compare plusieurs approches de simulation d'un signal Lidar sur de la végétation forestière. Différents types de maquettes forestières plus ou moins réalistes sont simulées à partir de relevés de terrain. Une nouvelle façon de créer scènes est en particulier testée et validée. Elle consiste à représenter les scènes forestières à partir de données obtenues sur le terrain avec un lidar terrestre (TLS). Les scans TLS sont voxellisés et un indice de densité de végétation et calculé pour chaque voxel permettant ainsi une représentation détaillée de la structure en 3D de la végétation. Les signaux acquis par un Lidar aéroporté sont ensuite simulés par transfert radiatif à l’aide du modèle DART, développé par le Cesbio. Les résultats obtenus sont comparés à des données lidar expérimentales pour les sites où ces données sont disponibles afin de valider les approches de simulation. La validation reste cependant relative à ce stade car le travail sur la calibration radiométrique du système Lidar aéroporté n’a pu être finalisée avec les informations disponibles. Une étude de sensibilité du signal simulé à différents paramètres environnementaux et système est ensuite menée afin de comprendre l’impact de ces paramètres sur la qualité du signal. Certaines recommandations préliminaires pour le dimensionnement d’un système lidar spatial pour le suivi de la végétation peuvent être déduites de ces analyses