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Molnos, S., Mamdouh, T., Petri, S., Nocke, T., Weinkauf, T. & Coumou, D. (2017). A network-based detection scheme for the jet stream core. Earth System Dynamics, 8(1), 75-89
Open this publication in new window or tab >>A network-based detection scheme for the jet stream core
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2017 (English)In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 8, no 1, p. 75-89Article in journal (Refereed) Published
Abstract [en]

The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere midlatitudes. In particular, the polar jet is located between cold arctic air to the north and warmer subtropical air to the south. Strongly meandering states therefore often lead to extreme surface weather. Some algorithms exist which can detect the 2-D (latitude and longitude) jets' core around the hemisphere, but all of them use a minimal threshold to determine the subtropical and polar jet stream. This is particularly problematic for the polar jet stream, whose wind velocities can change rapidly from very weak to very high values and vice versa. We develop a network-based scheme using Dijkstra's shortest-path algorithm to detect the polar and subtropical jet stream core. This algorithm not only considers the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states. The parameter values of the detection scheme are optimized using simulated annealing and a skill function that accounts for the zonal-mean jet stream position (Rikus, 2015). After the successful optimization process, we apply our scheme to reanalysis data covering 1979-2015 and calculate seasonal-mean probabilistic maps and trends in wind strength and position of jet streams. We present longitudinally defined probability distributions of the positions for both jets for all on the Northern Hemisphere seasons. This shows that winter is characterized by two well-separated jets over Europe and Asia (ca. 20 degrees W to 140 degrees E). In contrast, summer normally has a single merged jet over the western hemisphere but can have both merged and separated jet states in the eastern hemisphere. With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and it is therefore very suitable to analyze jet stream patterns in observations and models, enabling more advanced model-validation.

Place, publisher, year, edition, pages
COPERNICUS GESELLSCHAFT MBH, 2017
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-204085 (URN)10.5194/esd-8-75-2017 (DOI)000395096400001 ()2-s2.0-85012177481 (Scopus ID)
Note

QC 20170329

Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2018-01-13Bibliographically approved
Saikia, H. & Weinkauf, T. (2017). Global Feature Tracking and Similarity Estimation in Time-Dependent Scalar Fields. Paper presented at 19th Eurographics/IEEE VGTC Conference on Visualization (EuroVis), JUN 12-16, 2017, Barcelona, SPAIN. Computer graphics forum (Print), 36(3), 1-11
Open this publication in new window or tab >>Global Feature Tracking and Similarity Estimation in Time-Dependent Scalar Fields
2017 (English)In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, Vol. 36, no 3, p. 1-11Article in journal (Refereed) Published
Abstract [en]

We present an algorithm for tracking regions in time-dependent scalar fields that uses global knowledge from all time steps for determining the tracks. The regions are defined using merge trees, thereby representing a hierarchical segmentation of the data in each time step. The similarity of regions of two consecutive time steps is measured using their volumetric overlap and a histogram difference. The main ingredient of our method is a directed acyclic graph that records all relevant similarity information as follows: the regions of all time steps are the nodes of the graph, the edges represent possible short feature tracks between consecutive time steps, and the edge weights are given by the similarity of the connected regions. We compute a feature track as the global solution of a shortest path problem in the graph. We use these results to steer the - to the best of our knowledge - first algorithm for spatio-temporal feature similarity estimation. Our algorithm works for 2D and 3D time-dependent scalar fields. We compare our results to previous work, showcase its robustness to noise, and exemplify its utility using several real-world data sets.

Place, publisher, year, edition, pages
WILEY, 2017
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-211404 (URN)10.1111/cgf.13163 (DOI)000404881200003 ()2-s2.0-85022191409 (Scopus ID)
Conference
19th Eurographics/IEEE VGTC Conference on Visualization (EuroVis), JUN 12-16, 2017, Barcelona, SPAIN
Note

QC 20170804

Available from: 2017-08-04 Created: 2017-08-04 Last updated: 2018-01-13Bibliographically approved
Micallef, L., Palmas, G., Oulasvirta, A. & Weinkauf, T. (2017). Towards Perceptual Optimization of the Visual Design of Scatterplots. Paper presented at IEEE Pacific Visualization Symposium (IEEE PacificVis), APR 18-21, 2017, Seoul Natl Univ, Seoul, SOUTH KOREA. IEEE Transactions on Visualization and Computer Graphics, 23(6), 1588-1599
Open this publication in new window or tab >>Towards Perceptual Optimization of the Visual Design of Scatterplots
2017 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 23, no 6, p. 1588-1599Article in journal (Refereed) Published
Abstract [en]

Designing a good scatterplot can be difficult for non-experts in visualization, because they need to decide on many parameters, such as marker size and opacity, aspect ratio, color, and rendering order. This paper contributes to research exploring the use of perceptual models and quality metrics to set such parameters automatically for enhanced visual quality of a scatterplot. A key consideration in this paper is the construction of a cost function to capture several relevant aspects of the human visual system, examining a scatterplot design for some data analysis task. We show how the cost function can be used in an optimizer to search for the optimal visual design for a user's dataset and task objectives (e.g., "reliable linear correlation estimation is more important than class separation"). The approach is extensible to different analysis tasks. To test its performance in a realistic setting, we pre-calibrated it for correlation estimation, class separation, and outlier detection. The optimizer was able to produce designs that achieved a level of speed and success comparable to that of those using human-designed presets (e.g., in R or MATLAB). Case studies demonstrate that the approach can adapt a design to the data, to reveal patterns without user intervention.

Place, publisher, year, edition, pages
IEEE Computer Society, 2017
Keyword
Scatterplot, optimization, perception, crowdsourcing
National Category
Computer Sciences
Identifiers
urn:nbn:se:kth:diva-207870 (URN)10.1109/TVCG.2017.2674978 (DOI)000400527500003 ()28252407 (PubMedID)2-s2.0-85009453141 (Scopus ID)
Conference
IEEE Pacific Visualization Symposium (IEEE PacificVis), APR 18-21, 2017, Seoul Natl Univ, Seoul, SOUTH KOREA
Note

QC 20170530

Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2018-01-13Bibliographically approved
Wang, Z., Seidel, H.-P. -. & Weinkauf, T. (2016). Multi-field Pattern Matching based on Sparse Feature Sampling. IEEE Transactions on Visualization and Computer Graphics, 22(1), 807-816
Open this publication in new window or tab >>Multi-field Pattern Matching based on Sparse Feature Sampling
2016 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 22, no 1, p. 807-816Article in journal (Refereed) Published
Abstract [en]

We present an approach to pattern matching in 3D multi-field scalar data. Existing pattern matching algorithms work on single scalar or vector fields only, yet many numerical simulations output multi-field data where only a joint analysis of multiple fields describes the underlying phenomenon fully. Our method takes this into account by bundling information from multiple fields into the description of a pattern. First, we extract a sparse set of features for each 3D scalar field using the 3D SIFT algorithm (Scale-Invariant Feature Transform). This allows for a memory-saving description of prominent features in the data with invariance to translation, rotation, and scaling. Second, the user defines a pattern as a set of SIFT features in multiple fields by e.g. brushing a region of interest. Third, we locate and rank matching patterns in the entire data set. Experiments show that our algorithm is efficient in terms of required memory and computational efforts.

Keyword
Convolution, Correlation, Data visualization, Feature extraction, Jacobian matrices, Pattern matching, Three-dimensional displays
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184847 (URN)10.1109/TVCG.2015.2467292 (DOI)000364043400086 ()2-s2.0-84947094032 (Scopus ID)
Note

QC 20160404

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Saikia, H., Seidel, H.-P. & Weinkauf, T. (2015). Fast Similarity Search in Scalar Fields using Merging Histograms. In: Topological Methods in Data Analysis and Visualization IV: Theory, Algorithms, and Applications. Paper presented at TopoInVis 2015, May 20-22 (pp. 121-134). Paper presented at TopoInVis 2015, May 20-22. Springer
Open this publication in new window or tab >>Fast Similarity Search in Scalar Fields using Merging Histograms
2015 (English)In: Topological Methods in Data Analysis and Visualization IV: Theory, Algorithms, and Applications, Springer, 2015, p. 121-134Chapter in book (Refereed)
Abstract [en]

Similarity estimation in scalar fields using level set topology has attracted a lot of attention in the recent past. Most existing techniques match parts of contour or merge trees against each other by estimating a best overlap between them. Due to their combinatorial nature, these methods can be computationally expensive or prone to instabilities. In this paper, we use an inexpensive feature descriptor to compare subtrees of merge trees against each other. It is the data histogram of the voxels encompassed by a subtree. A small modification of the merge tree computation algorithm allows for obtaining these histograms very efficiently. Furthermore, the descriptor is robust against instabilities in the merge tree. The method is useful in an interactive environment, where a user can search for all structures similar to an interactively selected one. Our method is conservative in the sense that it finds all similar structures, with the rare occurrence of some false positives. We show with several examples the effectiveness, efficiency and accuracy of our method.

Place, publisher, year, edition, pages
Springer, 2015
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-213972 (URN)10.1007/978-3-319-44684-4_7 (DOI)2-s2.0-85020191758 (Scopus ID)9783319446820 (ISBN)
Conference
TopoInVis 2015, May 20-22
Note

QC 20160406

Available from: 2017-09-07 Created: 2017-09-07 Last updated: 2018-01-13Bibliographically approved
Wang, Z., Seidel, H.-P. -. & Weinkauf, T. (2015). Hierarchical Hashing for Pattern Search in 3D Vector Fields. In: Proc. Vision, Modeling and Visualization: . Paper presented at Vision, Modeling and Visualization (pp. 1-48).
Open this publication in new window or tab >>Hierarchical Hashing for Pattern Search in 3D Vector Fields
2015 (English)In: Proc. Vision, Modeling and Visualization, 2015, p. 1-48Conference paper, Published paper (Refereed)
Abstract [en]

The expressiveness of many visualization methods for 3D vector fields is often limited by occlusion, i.e., interesting flow patterns hide each other or are hidden by laminar flow. Automatic detection of patterns in 3D vector fields has gained attention recently, since it allows to highlight user-defined patterns and separate the wheat from the chaff. We propose an algorithm which is able to detect 3D flow patterns of arbitrary extent in a robust manner. We encode the local flow behavior in scale space using a sequence of hierarchical base descriptors, which are pre-computed and hashed into a number of hash tables. This ensures a fast fetching of similar occurrences in the flow and requires only a constant number of table lookups. In contrast to many previous approaches, our method supports patterns of arbitrary shape and extent. We achieve this by assembling these patterns using several smaller spheres. The results are independent of translation, rotation, and scaling. Our experiments show that our approach encompasses the state of the art with respect to both the computational costs and the accuracy.

National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184850 (URN)2-s2.0-85018270552 (Scopus ID)
Conference
Vision, Modeling and Visualization
Note

QC 20160405

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Bachynskyi, M., Palmas, G., Oulasvirta, A. & Weinkauf, T. (2015). Informing the Design of Novel Input Methods with Muscle Coactivation Clustering. ACM Transactions on Computer-Human Interaction, 21(6), Article ID 30.
Open this publication in new window or tab >>Informing the Design of Novel Input Methods with Muscle Coactivation Clustering
2015 (English)In: ACM Transactions on Computer-Human Interaction, ISSN 1073-0516, Vol. 21, no 6, article id 30Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel summarization of biomechanical and performance data for user interface designers. Previously, there was no simple way for designers to predict how the location, direction, velocity, precision, or amplitude of users’ movement affects performance and fatigue. We cluster muscle coactivation data from a 3D pointing task covering the whole reachable space of the arm. We identify eleven clusters of pointing movements with distinct muscular, spatio-temporal and performance properties. We discuss their use as heuristics when designing for 3D pointing.

Place, publisher, year, edition, pages
ACM Digital Library, 2015
Keyword
Muscle coactivation clustering, biomechanical simulation, physical ergonomics, user interface design, user performance
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184822 (URN)10.1145/2687921 (DOI)2-s2.0-84921466880 (Scopus ID)
Note

QC 20160408

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Bachynskyi, M., Palmas, G., Oulasvirta, A., Steimle, J. & Weinkauf, T. (2015). Performance and Ergonomics of Touch Surfaces: A Comparative Study Using Biomechanical Simulation. In: CHI '15: Proceedings of the 33rd Annual ACM Conference on Human Factors in Computing. Paper presented at ACM CHI Conference on Human Factors in Computing Systems (pp. 1817-1826). ACM Digital Library
Open this publication in new window or tab >>Performance and Ergonomics of Touch Surfaces: A Comparative Study Using Biomechanical Simulation
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2015 (English)In: CHI '15: Proceedings of the 33rd Annual ACM Conference on Human Factors in Computing, ACM Digital Library, 2015, p. 1817-1826Conference paper, Published paper (Refereed)
Abstract [en]

Although different types of touch surfaces have gained extensive attention in HCI, this is the first work to directly compare them for two critical factors: performance and ergonomics. Our data come from a pointing task (N=40) carried out on five common touch surface types: public display (large, vertical, standing), tabletop (large, horizontal, seated), laptop (medium, adjustably tilted, seated), tablet (seated, in hand), and smartphone (single- and two-handed input). Ergonomics indices were calculated from biomechanical simulations of motion capture data combined with recordings of external forces. We provide an extensive dataset for researchers and report the first analyses of similarities and differences that are attributable to the different postures and movement ranges.

Place, publisher, year, edition, pages
ACM Digital Library, 2015
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184848 (URN)10.1145/2702123.2702607 (DOI)
Conference
ACM CHI Conference on Human Factors in Computing Systems
Note

Received a Best Paper Honorable Mention. QC 20160408

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Brunton, A., Wand, M., Wuhrer, S., Seidel, H.-P. -. & Weinkauf, T. (2014). A Low-Dimensional Representation for Robust Partial Isometric Correspondences Computation. Graphical Models, 76(2), 70-85
Open this publication in new window or tab >>A Low-Dimensional Representation for Robust Partial Isometric Correspondences Computation
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2014 (English)In: Graphical Models, ISSN 1524-0703, E-ISSN 1524-0711, Vol. 76, no 2, p. 70-85Article in journal (Refereed) Published
Abstract [en]

Intrinsic shape matching has become the standard approach for pose invariant correspondence estimation among deformable shapes. Most existing approaches assume global consistency. While global isometric matching is well understood, only a few heuristic solutions are known for partial matching. Partial matching is particularly important for robustness to topological noise, which is a common problem in real-world scanner data. We introduce a new approach to partial isometric matching based on the observation that isometries are fully determined by local information: a map of a single point and its tangent space fixes an isometry. We develop a new representation for partial isometric maps based on equivalence classes of correspondences between pairs of points and their tangent-spaces. We apply our approach to register partial point clouds and compare it to the state-of-the-art methods, where we obtain significant improvements over global methods for real-world data and stronger guarantees than previous partial matching algorithms.

Place, publisher, year, edition, pages
Elsevier, 2014
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184824 (URN)10.1016/j.gmod.2013.11.003 (DOI)000347018500006 ()2-s2.0-84892751056 (Scopus ID)
Note

QC 20160405

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Palmas, G., Bachynskyi, M., Oulasvirta, A., Seidel, H.-P. -. & Weinkauf, T. (2014). An Edge-Bundling Layout for Interactive Parallel Coordinates. In: Proc. IEEE PacificVis: . Paper presented at IEEE PacificVis, Yokohama, Japan, March 4 - 7, 2014. IEEE
Open this publication in new window or tab >>An Edge-Bundling Layout for Interactive Parallel Coordinates
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2014 (English)In: Proc. IEEE PacificVis, IEEE , 2014Conference paper, Published paper (Refereed)
Abstract [en]

Parallel Coordinates is an often used visualization method for multidimensional data sets. Its main challenges for large data sets are visual clutter and overplotting which hamper the recognition of patterns in the data. We present an edge-bundling method using density-based clustering for each dimension. This reduces clutter and provides a faster overview of clusters and trends. Moreover, it allows rendering the clustered lines using polygons, decreasing rendering time remarkably. In addition, we design interactions to support multidimensional clustering with this method. A user study shows improvements over the classic parallel coordinates plot in two user tasks: correlation estimation and subset tracing.

Place, publisher, year, edition, pages
IEEE, 2014
National Category
Computer Sciences
Research subject
Computer Science; SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-184829 (URN)
Conference
IEEE PacificVis, Yokohama, Japan, March 4 - 7, 2014
Note

QC 20160425

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2018-01-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1498-9062

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