The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

C S T Daughtry - One of the best experts on this subject based on the ideXlab platform.

  • utility of an image based canopy reflectance Modeling Tool for remote estimation of lai and leaf chlorophyll content at the field scale
    Remote Sensing of Environment, 2009
    Co-Authors: Rasmus Houborg, Martha C Anderson, C S T Daughtry
    Abstract:

    Abstract This paper presents a physically-based approach for estimating critical variables describing land surface vegetation canopies, relying on remotely sensed data that can be acquired from operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) Modeling Tool couples leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths for the inverse retrieval of leaf chlorophyll content ( C ab ) and total one-sided leaf area per unit ground area (LAI). The inversion of the canopy reflectance model is constrained by assuming limited variability of leaf structure, vegetation clumping, and leaf inclination angle within a given crop field and by exploiting the added radiometric information content of pixels belonging to the same field. A look-up-table with a suite of pre-computed spectral reflectance relationships, each a function of canopy characteristics, soil background effects and external conditions, is accessed for fast pixel-wise biophysical parameter retrievals. Using 1 m resolution aircraft and 10 m resolution SPOT-5 imagery, REGFLEC effectuated robust biophysical parameter retrievals for a corn field characterized by a wide range in leaf chlorophyll levels and intermixed green and senescent leaf material. Validation against in-situ observations yielded relative root-mean-square deviations (RMSD) on the order of 10% for the 1 m resolution LAI (RMSD = 0.25) and C ab (RMSD = 4.4 μg cm − 2 ) estimates, due in part to an efficient correction for background influences. LAI and C ab retrieval accuracies at the SPOT 10 m resolution were characterized by relative RMSDs of 13% (0.3) and 17% (7.1 μg cm − 2 ), respectively, and the overall intra-field pattern in LAI and C ab was well established at this resolution. The developed method has utility in agricultural fields characterized by widely varying distributions of model variables and holds promise as a valuable operational Tool for precision crop management. Work is currently in progress to extend REGFLEC to regional scales.

Rasmus Houborg - One of the best experts on this subject based on the ideXlab platform.

  • utility of an image based canopy reflectance Modeling Tool for remote estimation of lai and leaf chlorophyll content at the field scale
    Remote Sensing of Environment, 2009
    Co-Authors: Rasmus Houborg, Martha C Anderson, C S T Daughtry
    Abstract:

    Abstract This paper presents a physically-based approach for estimating critical variables describing land surface vegetation canopies, relying on remotely sensed data that can be acquired from operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) Modeling Tool couples leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths for the inverse retrieval of leaf chlorophyll content ( C ab ) and total one-sided leaf area per unit ground area (LAI). The inversion of the canopy reflectance model is constrained by assuming limited variability of leaf structure, vegetation clumping, and leaf inclination angle within a given crop field and by exploiting the added radiometric information content of pixels belonging to the same field. A look-up-table with a suite of pre-computed spectral reflectance relationships, each a function of canopy characteristics, soil background effects and external conditions, is accessed for fast pixel-wise biophysical parameter retrievals. Using 1 m resolution aircraft and 10 m resolution SPOT-5 imagery, REGFLEC effectuated robust biophysical parameter retrievals for a corn field characterized by a wide range in leaf chlorophyll levels and intermixed green and senescent leaf material. Validation against in-situ observations yielded relative root-mean-square deviations (RMSD) on the order of 10% for the 1 m resolution LAI (RMSD = 0.25) and C ab (RMSD = 4.4 μg cm − 2 ) estimates, due in part to an efficient correction for background influences. LAI and C ab retrieval accuracies at the SPOT 10 m resolution were characterized by relative RMSDs of 13% (0.3) and 17% (7.1 μg cm − 2 ), respectively, and the overall intra-field pattern in LAI and C ab was well established at this resolution. The developed method has utility in agricultural fields characterized by widely varying distributions of model variables and holds promise as a valuable operational Tool for precision crop management. Work is currently in progress to extend REGFLEC to regional scales.

  • utility of an image based canopy reflectance Modeling Tool for remote estimation of lai and leaf chlorophyll content at regional scales
    Journal of Applied Remote Sensing, 2009
    Co-Authors: Rasmus Houborg, Martha C Anderson
    Abstract:

    This paper describes a novel physically-based approach for estimating leaf area index (LAI) and leaf chlorophyll content (Cab) at regional scales that relies on radiance data acquirable from a suite of aircraft and operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) Modeling Tool integrates leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths. REGFLEC adopts a multi-step LUT-based inversion approach and incorporates image-based techniques to reduce the confounding effects of land cover specific vegetation parameters and soil reflectance. REGFLEC was applied to agricultural and natural vegetation areas using 10 m and 20 m resolution SPOT imagery, and variable environmental and plant development conditions allowed for model validation over a wide range in LAI (0 - 6) and Cab (20 - 75 µg cm-2). Validation against in-situ measurements yielded relative root-mean-square deviations on the order of 13% (0.4) for LAI and between 11 - 19% (4.9 - 9.1 µg cm-2) for Cab. REGFLEC demonstrated good utility in detecting spatial and temporal variations in LAI and Cab without requiring site-specific data for calibration. The physical approach presented here can quite easily be applied to other regions and has the potential of being more universally applicable than traditional empirical approaches for retrieving LAI and Cab.

Janette Wong - One of the best experts on this subject based on the ideXlab platform.

  • applying patterns during business process Modeling
    Business Process Management, 2008
    Co-Authors: Thomas Gschwind, Jana Koehler, Janette Wong
    Abstract:

    Although the business process community has put a major emphasis on patterns, notably the famous workflow patterns, only limited support for using patterns in today's business process Modeling Tools can be found. While the basic workflow patterns for control flow are available in almost every business process Modeling Tool, there is no support for the user in correctly applying these simple patterns leading to many incorrectly modeled business processes. Only limited support for pattern compounds can be found in some Tools, there is no active support for selecting patterns that are applicable in some user-determined context, Tools do not give feedback to the user if applying a pattern can lead to a Modeling error, nor do they trace the sequence of applied patterns during the editing process. In this paper, we describe an extension of a business process Modeling Tool with patterns to provide these capabilities. We distinguish three scenarios of pattern application and discuss a set of pattern compounds that are based on the basic workflow patterns for control flow. We present an approach where business users receive help in understanding the context and consequences of applying a pattern.

Martha C Anderson - One of the best experts on this subject based on the ideXlab platform.

  • utility of an image based canopy reflectance Modeling Tool for remote estimation of lai and leaf chlorophyll content at the field scale
    Remote Sensing of Environment, 2009
    Co-Authors: Rasmus Houborg, Martha C Anderson, C S T Daughtry
    Abstract:

    Abstract This paper presents a physically-based approach for estimating critical variables describing land surface vegetation canopies, relying on remotely sensed data that can be acquired from operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) Modeling Tool couples leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths for the inverse retrieval of leaf chlorophyll content ( C ab ) and total one-sided leaf area per unit ground area (LAI). The inversion of the canopy reflectance model is constrained by assuming limited variability of leaf structure, vegetation clumping, and leaf inclination angle within a given crop field and by exploiting the added radiometric information content of pixels belonging to the same field. A look-up-table with a suite of pre-computed spectral reflectance relationships, each a function of canopy characteristics, soil background effects and external conditions, is accessed for fast pixel-wise biophysical parameter retrievals. Using 1 m resolution aircraft and 10 m resolution SPOT-5 imagery, REGFLEC effectuated robust biophysical parameter retrievals for a corn field characterized by a wide range in leaf chlorophyll levels and intermixed green and senescent leaf material. Validation against in-situ observations yielded relative root-mean-square deviations (RMSD) on the order of 10% for the 1 m resolution LAI (RMSD = 0.25) and C ab (RMSD = 4.4 μg cm − 2 ) estimates, due in part to an efficient correction for background influences. LAI and C ab retrieval accuracies at the SPOT 10 m resolution were characterized by relative RMSDs of 13% (0.3) and 17% (7.1 μg cm − 2 ), respectively, and the overall intra-field pattern in LAI and C ab was well established at this resolution. The developed method has utility in agricultural fields characterized by widely varying distributions of model variables and holds promise as a valuable operational Tool for precision crop management. Work is currently in progress to extend REGFLEC to regional scales.

  • utility of an image based canopy reflectance Modeling Tool for remote estimation of lai and leaf chlorophyll content at regional scales
    Journal of Applied Remote Sensing, 2009
    Co-Authors: Rasmus Houborg, Martha C Anderson
    Abstract:

    This paper describes a novel physically-based approach for estimating leaf area index (LAI) and leaf chlorophyll content (Cab) at regional scales that relies on radiance data acquirable from a suite of aircraft and operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) Modeling Tool integrates leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths. REGFLEC adopts a multi-step LUT-based inversion approach and incorporates image-based techniques to reduce the confounding effects of land cover specific vegetation parameters and soil reflectance. REGFLEC was applied to agricultural and natural vegetation areas using 10 m and 20 m resolution SPOT imagery, and variable environmental and plant development conditions allowed for model validation over a wide range in LAI (0 - 6) and Cab (20 - 75 µg cm-2). Validation against in-situ measurements yielded relative root-mean-square deviations on the order of 13% (0.4) for LAI and between 11 - 19% (4.9 - 9.1 µg cm-2) for Cab. REGFLEC demonstrated good utility in detecting spatial and temporal variations in LAI and Cab without requiring site-specific data for calibration. The physical approach presented here can quite easily be applied to other regions and has the potential of being more universally applicable than traditional empirical approaches for retrieving LAI and Cab.

Dimitri N Mavris - One of the best experts on this subject based on the ideXlab platform.

  • rapid state space Modeling Tool for rectangular wing aeroservoelastic studies
    AIAA SciTech 2015- Modeling and Simulation Technologies Conference, 2015
    Co-Authors: Peter M Suh, Howard J Conyers, Dimitri N Mavris
    Abstract:

    This paper introduces a Modeling and simulation Tool for aeroservoelastic analysis of rectangular wings with trailing edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio and number of control surfaces. A doublet lattice approach is taken to compute generalized forces. A rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The Tool is fully parameterized with default information so there is little required interaction with the model developer. Although, all parameters can be easily modified if desired.The focus of this paper is on Tool presentation, verification and validation. This process is carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this Tool. Therefore the flutter speed and frequency for a clamped plate are computed using V-g and V-f analysis. The computational results are compared to a previously published computational analysis and wind tunnel results for the same structure. Finally a case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to V-g and V-f analysis. This also includes the analysis of the model in response to a 1-cos gust.

  • rapid state space Modeling Tool for rectangular wing aeroservoelastic studies
    SciTech 2015, 2015
    Co-Authors: Peter M Suh, Howard J Conyers, Dimitri N Mavris
    Abstract:

    This paper introduces a Modeling and simulation Tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The Tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this paper is on Tool presentation, verification, and validation. These processes are carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this Tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.