Multi-scale Heterogeneity Research Articles

Integration of multiscale carbonate reservoir heterogeneities in reservoir simulation

Abstract The construction of robust reservoir models considering geological carbonate heterogeneities, such as fractures and vugs, upscaling and numerical flow simulation remains a challenge. This work performs a methodology aiming a suitable representation of flow simulation and upscaling techniques according to small and large scale carbonate reservoir heterogeneities. The methodology is applied to one specific flow unit type considering diffuse fractures, sub-seismic fractures and isolated vugs. The methodology follows four elementary steps: division of reservoir into flow units, geostatistical modeling, upscaling procedures and flow simulation modeling of carbonate reservoirs. Given the presence of multiscale geological features and computational limitations, the upscaling procedure is separated as a function of heterogeneities scale. The process is shown for one flow unit of a specific case where flow progress in matrix and fracture occur at different time steps which make the single porosity approach difficult. For regions of fractures not fully connected, the flow takes place in the matrix. A dual permeability flow model is the best approach since it can take into account both flow progresses in connected fracture networks and in matrix medium. The methodology has shown several advantages: sequential control over static properties and pseudo-functions integrated with upscaling procedure; definition of the accurate simulation flow model; and improvement of the integration of multiscale heterogeneities in reservoir simulation. This work presents a new methodology and analysis that can be useful for multidisciplinary areas.

Multiscale decomposition for heterogeneous land‐atmosphere systems

AbstractThe land‐atmosphere system is characterized by pronounced land surface heterogeneity and vigorous atmospheric turbulence both covering a wide range of scales. The multiscale surface heterogeneities and multiscale turbulent eddies interact nonlinearly with each other. Understanding these multiscale processes quantitatively is essential to the subgrid parameterizations for weather and climate models. In this paper, we propose a method for surface heterogeneity quantification and turbulence structure identification. The first part of the method is an orthogonal transform in the probability density function (PDF) domain, in contrast to the orthogonal wavelet transforms which are performed in the physical space. As the basis of the whole method, the orthogonal PDF transform (OPT) is used to asymptotically reconstruct the original signals by representing the signal values with multilevel approximations. The “patch” idea is then applied to these reconstructed fields in order to recognize areas at the land surface or in turbulent flows that are of the same characteristics. A patch here is a connected area with the same approximation. For each recognized patch, a length scale is then defined to build the energy spectrum. The OPT and related energy spectrum analysis, as a whole referred to as the orthogonal PDF decomposition (OPD), is applied to two‐dimensional heterogeneous land surfaces and atmospheric turbulence fields for test. The results show that compared to the wavelet transforms, the OPD can reconstruct the original signal more effectively, and accordingly, its energy spectrum represents the signal's multiscale variation more accurately. The method we propose in this paper is of general nature and therefore can be of interest for problems of multiscale process description in other geophysical disciplines.

Multi-scale phylogenetic heterogeneity of archaea, bacteria, methanogens and methanotrophs in lake sediments

Understanding spatial microbial community variation is necessary to assess diversity patterns. In this study, we investigated spatial heterogeneity and variability of functional and total microbial benthic community structures in Lake Bourget, France. Community structure variability was determined vertically by comparing three sediment layers per core, and horizontally at the intra-site level (between up to three cores per sites) and between three sites. Bacterial, archaeal, methanotrophs and methanogens community structures were assessed by genotyping the 16S rRNA–23S rRNA intergenic spacer, 16S rRNA, pmoA and mcrA genes, respectively. The consequence of pooling DNA extracts before genotyping was tested. After pooling, the OTU number decreased for all communities, but it had no effect on structure. At the core scale, bacterial community structure significantly differed between the sediment layers, but archaeal, methanogens and methanotrophs community structures only differed significantly between the superficial and deeper layers. Changes in environmental conditions affected microbial community structures between sites (sediment carbonates, total carbon contents, median particle sizes, and water O2 saturation), but not intra-site, as no significant changes were observed at the horizontal scale. These spatial scales should be considered to understand their importance for biogeochemical cycle when assessing benthic microbial community structure and diversity in lakes.

Multiscale Conformational Heterogeneity in Staphylococcal Protein A: Possible Determinant of Functional Plasticity

The Staphylococcus aureus virulence factor staphylococcal protein A (SpA) is a major contributor tobacterial evasion of the host immune system, through high-affinity binding to host proteins suchas antibodies. SpA includes five small three-helix-bundle domains (E-D-A-B-C) separated by conserved flexible linkers. Prior attempts to crystallize individual domains in the absence of a binding partner have apparently been unsuccessful. There have also been no previous structures of tandem domains. Here we report the high-resolution crystal structures of a single C domain, and of two B domains connected by the conserved linker. Both structures exhibit extensive multiscale conformational heterogeneity, which required novel modeling protocols. Comparison of domain structures shows that helix1 orientation is especially heterogeneous, coordinated with changes in side chain conformational networks and contacting protein interfaces. This represents the kind of structural plasticity that could enable SpA to bind multiple partners.

Refraction of the principal stress trajectories and the stress jumps on faults and contact surfaces: Part 1. Non-constrained regular trajectories

Refraction of the principal stress trajectories and the stress jumps on faults and contact surfaces: Part 1. Non-constrained regular trajectories

EMMS-based discrete particle method (EMMS–DPM) for simulation of gas–solid flows

Understanding the hydrodynamics of gas–solid flows is a grand challenge in mechanical and chemical engineering. The continuum-based two-fluid models (TFM) are currently not accurate enough to describe the multi-scale heterogeneity, while the discrete particle method (DPM) following the trajectory of each particle is computationally infeasible for industrial systems. Following our previous work, we report in this article a coarse-grained DPM considering the meso-scale structure based on the energy-minimization multi-scale (EMMS) model, which can be orders of magnitude faster than the traditional DPM and can take full advantage of CPU–GPU (graphics processing unit) hybrid supercomputing. The size and solids concentration of the coarse-grained particles (CGP), as well as their interactions with the gas flow (the drag) are determined by the EMMS model with a two-phase decomposition. The interactions between CGPs are determined according to the kinetic theory of granular flows (KTGF). The method is tested by simulating the onset of fluidization and the steady state flow in lab-scale circulating fluidized bed (CFB) risers with different geometries and operating conditions both in 2D and 3D. The results agree well with experiments and traditional DPM based on single particles. The prospect of this method as a higher-resolution alternative to TFM for engineering applications and even for virtual process engineering is discussed finally.

High-strength and high-ductility nanostructured and amorphous metallic materials.

The development of materials with dual properties of high strength and high ductility has been a constant challenge since the foundation of the materials science discipline. The rapid progress of nanotechnology in recent decades has further brought this challenge to a new era. This Research News highlights a few newly developed strategies to optimize advanced nanomaterials and metallic glasses with exceptional dual mechanical properties of high strength and high ductility. A general concept of strain non-localization is presented to describe the role of multiscale (i.e., macroscale, microscale, nanoscale, and atomic scale) heterogeneities in the ductility enhancement of materials reputed to be intrinsically brittle, such as nanostructured metallic materials and bulk metallic glasses. These nanomaterials clearly form a new group of materials that display an extraordinary relationship between yield strength and the uniform elongation with the same chemical composition. Several other examples of nanomaterials such as those reinforced by nanoprecipitates will also be described.

Rationalization of Microstructure Heterogeneity in INCONEL 718 Builds Made by the Direct Laser Additive Manufacturing Process

Simulative builds, typical of the tip-repair procedure, with matching compositions were deposited on an INCONEL 718 substrate using the laser additive manufacturing process. In the as-processed condition, these builds exhibit spatial heterogeneity in microstructure. Electron backscattering diffraction analyses showed highly misoriented grains in the top region of the builds compared to those of the lower region. Hardness maps indicated a 30 pct hardness increase in build regions close to the substrate over those of the top regions. Detailed multiscale characterizations, through scanning electron microscopy, electron backscattered diffraction imaging, high-resolution transmission electron microscopy, and ChemiSTEM, also showed microstructure heterogeneities within the builds in different length scales including interdendritic and interprecipitate regions. These multiscale heterogeneities were correlated to primary solidification, remelting, and solid-state precipitation kinetics of γ″ induced by solute segregation, as well as multiple heating and cooling cycles induced by the laser additive manufacturing process.

Semi-Analytical Proxy for Vapex Process Modeling in Heterogeneous Reservoirs

Vapex (vapor extraction) is a nonthermal process that has significant potential in providing a more environmentally friendly and energy-efficient alternative to steam injection. Vaporized solvent injected in-situ dissolves into the oil and reduces oil viscosity, allowing the oil to flow to a horizontal production well via gravitational forces. While compositional simulators are available for assessing the Vapex performance, the simulation process may become difficult when taking into account the uncertainty due to reservoir heterogeneity. A semi-analytical proxy is proposed to model the process, in a way analogous to the steam-assisted gravity drainage (SAGD) model described by Butler, who demonstrated the similarity between two processes with a series of Hele-Shaw experiments and derived an analytical steady-state flow rate relationship that is comparable with the SAGD case. Solvent concentration and intrinsic diffusivity are introduced in this model instead of temperature and thermal diffusivity in SAGD. In this paper, analytical solutions and implementation details for the Vapex proxy are presented. The proposed approach is then applied to various reservoirs discretized with spatially varying rock porosity and permeability values; bitumen drainage rate and solvent penetration are calculated sequentially at grid blocks along the solvent–bitumen interface over incremental time steps. Results from this model are compared against experimental data available in the literature as well as detailed compositional simulation studies. Computational requirement of the proxy in comparison with numerical simulations is also emphasized. An important contribution from this work is that process physics are built directly into this proxy, giving it an advantage over other data-driven modeling approaches (e.g., regression). It can be used as an efficient alternative to expensive detailed flow simulations. It presents an important potential for assessing the uncertainty due to multiscale heterogeneity on effective mass transfer and the resulting recovery performance, as well as assisting decisions-making for future pilot and field development.

Epigeal arthropod communities in intensively farmed landscapes: Effects of land use mosaics, neighbourhood heterogeneity, and field position

Trophic guilds of epigeal arthropods regulating insect pest populations may be affected by factors acting across spatial scales. Although the influence of landscape factors associated with farming effects on arthropod assemblages has received increasing attention in the last decades, most research was carried out in fine-grain landscapes by comparing conventional and organic cropping systems. Here, we aimed at identifying the role of fencerows and crop heterogeneity in defining arthropod diversity in intensively farmed, coarse-grain landscapes. Hence, we developed a multi-scale heterogeneity approach based on fitting linear-mixed models to elucidate the effects of three spatial scales (local, neighbouring crop types, and landscape) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 22 field pairs. Field position was a major determinant of arthropod species diversity at local scale, due to the contrasting disturbance regimes of fencerows and adjoining field edges. Fence density at landscape scale contributed to retain diverse arthropod assemblages in farmland mosaics by supplying habitats and refuges. In addition, extended fence network may function as corridors for dispersal, increasing connectivity between dissimilar habitats. Fence habitats, as well as their density in the landscapes, enhance both richness and abundance of beneficial arthropods. Our findings indicate that the overall arthropod diversity was benefited by landscape complexity, being the presence and density of fencerows key landscape attributes. Contrasting disturbance regimes at different field positions emerged as a major driver modulating arthropod species diversity in intensively managed farmland mosaics. Non-cropped habitats associated with fencerows and field margins play key ecological functions that are of vital importance for providing ecosystem services in agro-ecosystems. Complex landscapes may help to conserve overall plant diversity in agro-ecosystems, as well as the spillover of arthropod species from fencerows towards crop fields. Even in heavily intensified landscapes, where crop diversity is the main source of heterogeneity, promoting measures intended for both restoring and managing fencerow and non-cropped habitats through landscape planning will contribute to maintain arthropod richness (almost 70% of total richness) across the entire landscape.

Retrieving past geodynamic events by unlocking rock archives with μ-XRF and μ-spectroscopy

Rocks are commonly polycrystalline systems presenting multi-scale chemical and structural heterogeneities inherited from crystallization processes or successive metamorphic events. This work illustrates how spatially resolved analytical techniques coupled with thermodynamic approaches allow rock compositional variations to be related to large-scale geodynamic processes. Emphasis is placed on the contribution of quantitative chemical imaging to the study of 2.2-2.0 Gy old metamorphic rocks from the West African Craton. A thorough analysis of elemental chemical maps acquired on rock thin sections enabled high pressure relic minerals to be located and re-analyzed later with precise point analyses. The pressure-temperature conditions of crystallization calculated from these analyses are typical of modern subduction zones. These results push back the onset of modern-style plate tectonics to 2.15 Gy, i.e. more than one billion years earlier than was consensually accepted. The second part of the paper describes the imaging capabilities offered by the new ultra-bright diffraction limited synchrotron sources. Experimental data acquired with the Maia detector at beamline P06 at Petra III as well as simulations of μ-XRF spectra that will be generated at the SRX beamline at NSLS-II are presented. These results demonstrate that cm2 large chemical maps can be acquired with submicron spatial resolution and a precision suitable for thermobarometric estimates, with dwell time smaller than 1 millisecond. The last part of the paper discusses the relevance of utilizing recent X-ray fluorescence nanoprobes for diagenetic to low grade metamorphism applications.

Scaling of surface soil moisture over heterogeneous fields subjected to a single rainfall event

Determining surface soil moisture evolution over a range of scales remains a challenge because of multi-scale heterogeneity exhibited by soils. Measurement techniques are not in accordance with the scales at which information on soil moisture is needed. In situ point measurements are expensive and provide information only at a few select points. On the other hand, the spatial resolution of remote sensing data is too coarse for hydrologic applications. Currently, surface soil moisture evolution for heterogeneous fields subjected to rainfall conditions is achieved by a computationally intensive numerical solution of the Richards equation. To describe surface soil moisture evolution at local- and field-scale in an efficient manner, reference scaling curves are developed in this study based on a sharp front approximation and by adopting a log-normally distributed spatial hydraulic conductivity field. These scaling curves facilitate the determination of temporal evolution of surface soil moisture at any unmeasured location in the field, and can be used to obtain the field-scale surface soil moisture evolution for a single rainfall event. The scaling curves are computationally straight forward, and reduce the need for extensive soil moisture measurements at numerous locations in the field. Comparisons with experimental and numerical simulation results show that the proposed scaling curves hold promise for describing mean surface soil moisture evolution at the field-scale.

Constraints from sulfur isotopes on the origin of gypsum at concrete/claystone interfaces

Two in situ concrete/claystone interfaces were sampled at the laboratory level in the Andra Meuse/Haute Marne (France) Underground Research Laboratory (URL) in order to study five years of interactions between Callovian–Oxfordian (COx) claystone and two cementitious materials (concrete bottom slab and shotcrete on the walls of the main gallery), with a specific focus on sulfur. Combined mineralogical, chemical and sulfur isotopic investigations were carried out to define the degree of the perturbation of the sulfur system in the claystone and in both the cementitious materials. At both interfaces, results show that the main perturbation on the claystone side is the formation of scarce μm-sized gypsum, the sulfur content of which is essentially derived from pyrite oxidation. The distribution of gypsum is highly correlated with the fissure network of the damaged zone due to excavation of the gallery. Its presence is also often associated with a loss of cohesion of the concrete/claystone interface. Due to the small amounts of gypsum and its μm-size, measurements were performed by ion microprobe. Adaptations were needed on account of the reactivity of gypsum and sulfates in general under the beam. The use of ion microprobe analysis provided evidence of high local isotopic heterogeneity that could be attributed to kinetic fractionation effects. Some analyses suggest a minor contribution of dissolved sulfates in pore water of claystone and possibly of concrete. The perturbation on the concrete side is marked by a significant increase in the bulk sulfur content within three millimeters of the interface with the claystone, showing a sulfur gradient from claystone to concrete. The main objective of this work was to define the extent of the chemical and mineralogical perturbations, taking into account in situ URL conditions, i.e. hydrodynamic conditions (shotcrete sprayed on the gallery walls and subjected to ventilation of the galleries), damaged zone of claystone induced by excavation and multi-scale heterogeneity. This identifies the relevant parameters to better constrain predictive reactive transport models of concrete/claystone interactions at a realistic scale.

Data capture for multiscale modelling of the Lourinhã Formation, Lusitanian Basin, Portugal: an outcrop analogue for the Statfjord Group, Norwegian North Sea

Abstract Current recovery from the Statfjord Group in the majority of the fields on the Tampen Spur is less than 50%. A contributing factor to this is an incomplete understanding of multiscale heterogeneities, their distributions within a range of fluvial geobodies and their lateral extent and morphology in inter-well areas. Sedimentary heterogeneities have been modelled, together with petrophysical parameters, at a variety of scales. The modelled properties at a given scale were upscaled to the next level of heterogeneity, thus better honouring effective property values. The use of outcrop analogues is still a key tool for understanding facies relationships and the stratigraphic development of subsurface hydrocarbon-bearing reservoirs. The Lourinhã Formation, Portugal, was used as an analogue to collect both qualitative and quantitative data consistently following a three-phase workflow to capture data at various scales of heterogeneity. Traditional field data collection techniques have been supplemented with the collection of LiDAR data. A digital workflow utilizing interlinked datasets facilitates rapid data analysis and better data visualization with results that are more easily utilized in multiscale modelling studies. These scaled models were used to increase our understanding of the effect on flow of lithofacies and facies association distributions together with internal architectural elements and heterogeneities.

Multiscale deformation heterogeneity in twinning magnesium investigated with in situ image correlation

The complex strain fields that emerge at the onset of extensive deformation twinning in Magnesium alloy AZ31B has been investigated in situ with multiscale digital image correlation (DIC). A two camera setup has been used to yield full-field deformation maps on two orthogonal faces of a gradually strained compression sample whose crystallographic texture favors the {101¯2}〈1¯011〉 tensile twin mode. Deformation fields have been determined at subgrain resolution (DIC subset and nominal grain size, 12 and 50μm, respectively) on the primary examination face that is scanned with a microscopic lens at each load. In an in situ setting, a unique combination of microscopic DIC resolution and statistical significance (∼5000 grains) is achieved that enables a full bridging of the crystallite and sample scales at each load point. Intense strain heterogeneity is revealed abruptly at all length scales in the form of ±45° banded strain patterns: at the macroscale, the strain in the sample is locally accommodated by the sudden emergence/advance of shear bands whose macroscale strain content at initiation is around 1%. Bands from conjugate +45° and −45° families exhibit sequential activation. At the granular scale, another set of ±45° strain patterns are resolved inside a macroscopic band of either family with very high strain heterogeneity levels, whose extent is comparable to the twin transformation strain (principal values ±6.5%). Traversing the initial regions of the twin plateau in fine steps with in situ observation, the strain heterogeneity is found to explode, rather than gradually evolve, yielding uniquely shaped strain histograms at the subgrain scale which persist until the next macroscopic band arrives at the particular locality.

Multiscale Heterogeneity of Bone Microporosities and Tissue Scaffolds

Our aim was to use stereology to quantify the volume fraction of osteocyte lacunes, volume fraction of large blood vessels, numerical density of osteocyte lacunes, volume of osteocyte lacunae and bone surface in series of micro-CT images representing samples of spongy and compact bone of human tibia. The spongy bone had a smaller volume fraction of osteocyte lacunes, a greater numerical density of bone lacunes, a smaller volume of the lacunes within the same bone volume and a greater bone surface density when compared to the compact bone. Stereology provided us with data on hierarchical organization of bone structural heterogeneity with reasonable time costs.

Spatial Heterogeneity in the Strength of Plant-Herbivore Interactions under Predation Risk: The Tale of Bison Foraging in Wolf Country

Spatial heterogeneity in the strength of trophic interactions is a fundamental property of food web spatial dynamics. The feeding effort of herbivores should reflect adaptive decisions that only become rewarding when foraging gains exceed 1) the metabolic costs, 2) the missed opportunity costs of not foraging elsewhere, and 3) the foraging costs of anti-predator behaviour. Two aspects of these costs remain largely unexplored: the link between the strength of plant-herbivore interactions and the spatial scale of food-quality assessment, and the predator-prey spatial game. We modeled the foraging effort of free-ranging plains bison (Bison bison bison) in winter, within a mosaic of discrete meadows. Spatial patterns of bison herbivory were largely driven by a search for high net energy gains and, to a lesser degree, by the spatial game with grey wolves (Canis lupus). Bison decreased local feeding effort with increasing metabolic and missed opportunity costs. Bison herbivory was most consistent with a broad-scale assessment of food patch quality, i.e., bison grazed more intensively in patches with a low missed opportunity cost relative to other patches available in the landscape. Bison and wolves had a higher probability of using the same meadows than expected randomly. This co-occurrence indicates wolves are ahead in the spatial game they play with bison. Wolves influenced bison foraging at fine scale, as bison tended to consume less biomass at each feeding station when in meadows where the risk of a wolf's arrival was relatively high. Also, bison left more high-quality vegetation in large than small meadows. This behavior does not maximize their energy intake rate, but is consistent with bison playing a shell game with wolves. Our assessment of bison foraging in a natural setting clarifies the complex nature of plant-herbivore interactions under predation risk, and reveals how spatial patterns in herbivory emerge from multi-scale landscape heterogeneity.

Heihe Watershed Allied Telemetry Experimental Research (HiWATER): Scientific Objectives and Experimental Design

A major research plan entitled “Integrated research on the ecohydrological process of the Heihe River Basin” was launched by the National Natural Science Foundation of China in 2010. One of the key aims of this research plan is to establish a research platform that integrates observation, data management, and model simulation to foster twenty-first-century watershed science in China. Based on the diverse needs of interdisciplinary studies within this research plan, a program called the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) was implemented. The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a world-class watershed observing system, and to enhance the applicability of remote sensing in integrated ecohydrological studies and water resource management at the basin scale. This paper introduces the background, scientific objectives, and experimental design of HiWATER. The instrumental setting and airborne mission plans are also outlined. The highlights are the use of a flux observing matrix and an eco-hydrological wireless sensor network to capture multiscale heterogeneities and to address complex problems, such as heterogeneity, scaling, uncertainty, and closing water cycle at the watershed scale. HiWATER was formally initialized in May 2012 and will last four years until 2015. Data will be made available to the scientific community via the Environmental and Ecological Science Data Center for West China. International scientists are welcome to participate in the field campaign and use the data in their analyses.

Evaluation of representative elementary volume for a vuggy carbonate rock—Part: Porosity, permeability, and dispersivity

Abstract This work highlights variation in petrophysical properties of a macroporous vugular carbonate rock. The macroporosity consists of vugs and moldic pores with sizes ranging from mm to cm scale. Carbonate rocks exhibit multi-scale heterogeneities that make the understanding of fluid flow and recovery a challenge. Properties such as porosity and absolute permeability often vary within a volume and sampling at the representative elementary volume (REV) is needed to determine the appropriate continuum properties for reservoir characterization and prediction. A classical approach to examine the variation with rock sample size and the REV is through analysis at different scales. Measuring petrophysical properties at various scales has therefore been a part of the REV investigation for the studied material. To study the variation with sample size and the effect of heterogeneities on fluid flow, laboratory tests were conducted at different scales, ranging from cm to m scale. Totally 37 sub-samples of a large outcrop block with different sizes and shapes have been included in this work. The main objective has been to determine porosity, effective permeability and dispersivity as function of rock sample size. Porosity–permeability correlations for heterogeneous material can be inadequate and strongly scale dependant. Thus, we also investigate the variation of the porosity–permeability ratio with sample size. The experimental results show that the variance and coefficient of variation decreases with increase in sample size for all investigated properties. Based on the reduction of variation with increased rock sample size a representative volume for measurement is proposed for the studied material. The results also indicate less variation for the porosity–permeability relationship with increased sample volume. It is shown that a single measurement at traditional laboratory scale can lead to erroneous interpretation of a measured property for the vuggy carbonate material. However, multiple measurements at laboratory scale can be used to determine the representative properties.

TECHNICAL SPECIFICATION FOR THE VALIDATION OF REMOTE SENSING PRODUCTS

Abstract. The validation of remote sensing products (RSPs) is fundamental work before the proper use of RSPs. This paper mainly introduces the technical specification for the validation of remote sensing product, which is used to guide user how to validate the available products. The validation of remote sensing products (VRSP) mainly there are two levels. The first level focuses on the validation at pixel scale and the other is the product level which contains a number of pixels that are distributed in different land use types which are selected to represent both the space-time characteristics of surface parameters investigated. At pixel scale, the validation procedure mainly consists of three steps: sampling design for ground observation, data collection and estimation the mean value at pixel scale. The data types of ground observation include the wireless sensor network, which are used to capture multi-scale heterogeneities of surface parameters, and the footprint which could be a flux observation such as eddy covariance (EC) and large aperture scintillometer (LAS). After finishing the validation at pixel scale, the second-level validation for the whole remote sensing product is followed. The assessment with indexes is then used to evaluate the performance of the validation. Last, a validation report on the description of the validation will be included in the technical specification.