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Lars M. H. Ulander - One of the best experts on this subject based on the ideXlab platform.

  • Using the Two-Level Model with Tandem-X for Large-Scale Forest Mapping
    IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 2019
    Co-Authors: Henrik J. Persson, Maciej J. Soja, Johan E.s. Fransson, Lars M. H. Ulander
    Abstract:

    This study applies the two-Level Model to predict stem volume (VOL), presented as wall-to-wall rasters. The SAR data were acquired with the TanDEM-X system and 518 scenes covered the entire Sweden. For comparison, a multiple linear regression Model is also evaluated. Compared to earlier studies, the Model parameters are fitted separately for each satellite scene. The prediction accuracy at the stand-Level is evaluated using field inventoried reference stands within one scene, located in Northern Sweden and provided by a Swedish forest company. The results from the two Models were similar, with an RMSE of 34.8 m3/ha and 32.9 m3/ha at the stand-Level, respectively, and the corresponding biases were 14.3 m3/ha and 12.1 m3/ha. The error is significantly lower, compared to a previous study (52-65 m3/ha) where a universal multiple linear regression Model was used for all scenes. It can be concluded, that using Model parameters fitted at the local scene appears to improve the prediction performance in terms of RMSE, but no significant difference could be determined between predictions based on the two- Level Model or multiple linear regression, evaluated in this study.

  • Mapping and Modeling of boreal forest change in tandem-x data with the two-Level Model
    2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2017
    Co-Authors: Maciej J. Soja, Henrik J. Persson, Lars M. H. Ulander
    Abstract:

    In this paper, three approaches to forest change Modeling with the two-Level Model (TLM) are compared by fitting the TLM to 12 VV-polarized TanDEM-X acquisitions over a hemi-boreal test site in southern Sweden. It is observed that the best inversion results are obtained when rapid forest change (e.g., harvesting) is Modeled as change in canopy density, while growth is Modeled as change in forest height.

  • Mapping Topography and Forest Parameters in a Boreal Forest with Dual-Baseline TanDEM-X Data and the Two-Level Model
    Proceedings of EUSAR 2016: 11th European Conference on Synthetic Aperture Radar, 2016
    Co-Authors: Maciej J. Soja, Lars M. H. Ulander
    Abstract:

    In this paper, two-Level Model (TLM) inversion is used for unsupervised mapping of ground topography, forest height, and canopy density in boreal forests from dual-baseline, alternating bistatic mode TanDEM-X data. The TLM Models forest as two discrete scattering Levels, ground and vegetation, the latter with gaps. It is here shown using two alternating bistatic-mode TanDEM-X acquisitions made over the Swedish boreal test site Krycklan in September 2011 that the inverted TLM parameters can be used for mapping of ground topography and forest parameters.

  • estimation of forest biomass from two Level Model inversion of single pass insar data
    IEEE Transactions on Geoscience and Remote Sensing, 2015
    Co-Authors: Maciej J. Soja, Henrik J. Persson, Lars M. H. Ulander
    Abstract:

    A Model for aboveground biomass estimation from single-pass interferometric synthetic aperture radar (InSAR) data is presented. Forest height and canopy density estimates $\Delta h$ and $\eta_0$ , respectively, obtained from two-Level Model (TLM) inversion, are used as biomass predictors. Eighteen bistatic VV-polarized TanDEM-X (TDM) acquisitions are used, made over two Swedish test sites in the summers of 2011, 2012, and 2013 (nominal incidence angle: 41 $^{\circ} $ ; height-of-ambiguity: 32–63 m) . Remningstorp features a hemiboreal forest in southern Sweden, with flat topography and where 32 circular plots have been sampled between 2010 and 2011 (area: 0.5 ha; biomass: 42–242 t/ha; height: 14–32 m) . Krycklan features a boreal forest in northern Sweden, 720-km north–northeast from Remningstorp, with significant topography and where 31 stands have been sampled in 2008 (area: 2.4–26.3 ha; biomass: 23–183 t/ha; height: 7–21 m) . A high-resolution digital terrain Model has been used as ground reference during InSAR processing. For the aforementioned plots and stands and if the same acquisition is used for Model training and validation, the new Model explains 65%–89% of the observed variance, with root-mean-square error (RMSE) of 12%–19% (median: 15%) . By fixing two of the three Model parameters, accurate biomass estimation can also be done when different acquisitions or different test sites are used for Model training and validation, with RMSE of 12%–56% (median: 17%) . Compared with a simple scaling Model computing biomass from the phase center elevation above ground, the proposed Model shows significantly better performance in Remningstorp, as it accounts for the large canopy density variations caused by active management. In Krycklan, the two Models show similar performance.

  • Corrections to “Estimation of Forest Biomass From Two-Level Model Inversion of Single-Pass InSAR Data” {Sep 15 5083-5099]
    IEEE Transactions on Geoscience and Remote Sensing, 2015
    Co-Authors: Maciej Jerzy Soja, Henrik J. Persson, Lars M. H. Ulander
    Abstract:

    Presents corrections to the paper, "Estimation of forest biomass from two-Level Model inversion of single-pass InSAR data" (Soja, M.J., et al.,Trans. Geosci. Remote Sens., vol. 53, no. 9, pp. 5083–5099, Sep. 2015).

Sarah M. Ryan - One of the best experts on this subject based on the ideXlab platform.

  • A Tri-Level Model of Centralized Transmission and Decentralized Generation Expansion Planning for an Electricity Market—Part I
    IEEE Transactions on Power Systems, 2014
    Co-Authors: Sarah M. Ryan
    Abstract:

    We develop a tri-Level Model of transmission and generation expansion planning in a deregulated power market environment. Due to long planning/construction lead times and concerns for network reliability, transmission expansion is considered in the top Level as a centralized decision. In the second Level, multiple decentralized GENCOs make their own capacity expansion decisions while anticipating a wholesale electricity market equilibrium in the third Level. The collection of bi-Level games in the lower two Levels forms an equilibrium problem with equilibrium constraints (EPEC) that can be approached by either the diagonalization method (DM) or a complementarity problem (CP) reformulation. We propose a hybrid iterative solution algorithm that combines a CP reformulation of the tri-Level problem and DM solutions of the EPEC sub-problem.

Robert Brayton - One of the best experts on this subject based on the ideXlab platform.

  • Efficient uninterpreted function abstraction and refinement for word-Level Model checking
    2016 Formal Methods in Computer-Aided Design (FMCAD), 2016
    Co-Authors: Yen-sheng Ho, Pankaj Chauhan, Alan Mishchenko, Robert Brayton
    Abstract:

    Methods for word-Level Model checking based on purely bit-Level techniques have difficulties with heavy arithmetic logic. Word-Level and SMT approaches often are limited by relying on (incomplete) bounded Model checking. UFAR, a hybrid word- and bit-Level approach, addresses these issues, taking advantage of modern bit-Level sequential techniques while heavy arithmetic logic is addressed by word-Level abstraction and the use of uninterpreted function (UF) constraints. The methods and efficiency improvements developed for UFAR enabled it to prove 2422 of a set of 2492 industrial sequential Model checking problems within a 1-hour limit, while a bit-Level Model checker super prove completed only 2115 of these within the same limit.

Dmitry Shcherbin - One of the best experts on this subject based on the ideXlab platform.

Xin Leng - One of the best experts on this subject based on the ideXlab platform.

  • Research on dynamic water Level Model based on supercharged boiler
    2008 IEEE International Conference on Mechatronics and Automation, 2008
    Co-Authors: Xin Leng
    Abstract:

    For the Level control problem, the circulation process is analysed, a water Level Model for supercharged boiler is presented and the dynamic process is simulated. Steam-water mixture in a drum is divided into three volumes, thus the phenomenon that the water Level rapidly shrinks or swells due to the changing of pressure is captured. Using of the theory of thermal system and lumped parameter method, simplified physical Model and dynamic mathematical Model were established in a certain assuming and simplifying. Simulation studies show that the water Level will change with the change of the supercharged boiler load and the feed water. The results verify the accuracy and reliability of mathematical Model, which provides a theoretical basis for the follow-up control system design.

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