Browsing by Author "Bemis, Karen"

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    Framing the Challenges of Operational and Domain Usage of Volume Visualization Methods in Ocean Science
    (The Eurographics Association, 2020) Bemis, Karen; Gillmann, Christina and Krone, Michael and Reina, Guido and Wischgoll, Thomas
    Several case studies are used to explore why the adoption of visualization software, especially for the visualization of 3D timevarying ocean data, has lagged behind the development of visualization techniques. The development history of the Silver and Wang feature tracking for time-varying 3D volume data highlights the challenges of decadal scale development and support. The experiences of supporting operational use of processing and visualization for the COVIS oceanographic instrument suggest packaging and version control are far more critical than most users or developers in the ocean science community realize. Initial efforts to package feature extraction and skeletonization for a domain scientist lead to the realization that ease of configuration is critical to supporting scientific exploration, experimentation, and illustration. A consideration of the history of marching cubes focuses attention on the gap between the development of methods and the dissemination of fully mature software. These challenges can be framed succinctly as Discovery, Relevance, Adaptability for Ease of Usage, Input/Output Flexibility, Reliability, and Sustainability. The lessons learned here suggest the need for a more sustainable funding model, strong expectations for code dissemination and documentation, attention to the needs of users especially domain scientists, and greater visibility of code development efforts to end users.
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    A Hybrid 3D Eddy Detection Technique Based on Sea Surface Height and Velocity Field
    (The Eurographics Association, 2023) Hua, Weiping; Bemis, Karen; Kang, Dujuan; Ozer, Sedat; Silver, Deborah; Dutta, Soumya; Feige, Kathrin; Rink, Karsten; Zeckzer, Dirk
    Eddy detection is a critical task for ocean scientists to understand and analyze ocean circulation. In this paper, we introduce a hybrid eddy detection approach that combines sea surface height (SSH) and velocity fields with geometric criteria defining eddy behavior. Our approach searches for SSH minima and maxima, which oceanographers expect to find at the center of eddies. Geometric criteria are used to verify expected velocity field properties, such as net rotation and symmetry, by tracing velocity components along a circular path surrounding each eddy center. Progressive searches outward and into deeper layers yield each eddy's 3D region of influence. Isolation of each eddy structure from the dataset, using it's cylindrical footprint, facilitates visualization of internal eddy structures using horizontal velocity, vertical velocity, temperature and salinity. A quantitative comparison of Okubo-Weiss vorticity (OW) thresholding, the standard winding angle, and this new SSH-velocity hybrid methods of eddy detection as applied to the Red Sea dataset suggests that detection results are highly dependent on the choices of method, thresholds, and criteria. Our new SSH-velocity hybrid detection approach has the advantages of providing eddy structures with verified rotation properties, 3D visualization of the internal structure of physical properties, and rapid efficient estimations of eddy footprints without calculating streamlines. Our approach combines visualization of internal structure and tracking overall movement to support the study of the transport mechanisms key to understanding the interaction of nutrient distribution and ocean circulation. Our method is applied to three different datasets to showcase the generality of its application.