hig.sePublications
Change search
Refine search result
12 1 - 50 of 84
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andrée, Martin
    et al.
    Lantmäteriet.
    Larsson, Karolina
    KLM; Stockholms stad.
    Nordqvist Darell, Fanny
    Stockholms stad.
    Malm, Linus
    Tyréns.
    Tullberg, Odd
    WSP.
    Wallberg, Ann
    JM.
    Norsell, Johan
    NAI Svefa.
    Paasch, Jesper M.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Paulsson, Jenny
    Kungliga Tekniska Högskolan, Stockholm.
    Slutrapport för projektet Smart planering för byggande: Delprojekt 3 - BIM som informationsstöd för 3D fastighetsbildning2018Report (Other academic)
    Abstract [sv]

    Samhällsbyggnadsprocessen behöver utvecklas och bli smartare, öppnare och mer effektiv för ett ökat bostadsbyggande. En digitalisering av samhällsbyggnadsprocessen kan ge ett effektivare samarbete mellan kommun, fastighetsägare, byggherrar, medborgare, näringsliv och myndigheter.Vid bildande av tredimensionellt avgränsade fastigheter eller fastighetsutrymmen (3D-fastigheter) behöver gränsernas läge redovisas både verbalt och i kartor och ritningar, detsamma gäller berörda rättigheter. Det är idag ofta svårt att korrekt redovisa en 3D-volym med enbart dagens pappersritningar och även svårt att läsa en registerkarta i 2D med fastigheter och rättigheter beslutade i 3D. Beslutsunderlagen i fastighetsbildnings-processen behöver bli mer enhetliga och entydiga samt fastighetsinformationen behöver bli återanvändningsbar i hela samhällsbyggnadsprocessen.I detta projekt har vi studerat informationsbehovet i de olika tidpunkterna under fastighetsbildningsprocessen för 3D-fastigheter med fokus på vem som är ansvarig för att tillhandahålla informationsunderlag för att identifiera krav på utformning av 3D-modeller (t.ex BIM) och 3D-stöd för fastighetsbildning.Internationellt finns det ett stort intresse och många frågeställningar gällande samspelet mellan BIM och Fastighetsinformation; det är däremot ganska få fall som har identifierats där man har arbetat praktiskt med BIM i relation till redovisning av 3D-fastigheter.Projektethar även tittat på behov av visualisering och tillhandahållande av fastighetsinformation i 3D, hur informationen bör utformas för att kunna tolkas korrekt samt nyttjas vidare av andra aktörer i samhällsbyggnadsprocessen.Slutsatsen i projektetär att en framtida arbetsmodell där man i samband med myndighetsutövningen för fastighetsbildning samverkar med stöd av BIM och geografisk information i ärendehandläggningen kan ge stora effekter på både myndighetens effektivitet och i ärendeutövningen och för förståelsen av fastighetbildningsbeslutet hos samtliga intressenter i processen. För att det arbete som genomförts i denna utredning skall få genomslag i den dagliga verksamheten rekommenderar vibland annatatt de statliga och kommunala lantmäterimyndigheterna arbetar vidare med att utveckla arbetsprocessen och rekommendationerna för 3D-fastighetsbildning baserat på resultatet från detta projekt och redan i dagens modell efterfrågar att man i handläggningsprocessen kan arbeta BIM-baserat även om kommande beslutshandlingar under en övergångsperiod fortfarande kommer att vara baserade på ritningsbilagor i 2D.

  • 2.
    Andrée, Martin
    et al.
    Lantmäteriet.
    Paasch, Jesper M.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Paulsson, Jenny
    Kungliga Tekniska Högskolan.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    BIM and 3D property visualisation2018In: FIG Congress 2018: Proceedings, 2018, article id 9367Conference paper (Other academic)
    Abstract [en]

    The concept of 3D property has only existed a short period of time in Sweden, being introduced in 2004 and expanded in 2009 by the addition of condominium (apartment) ownership. It is therefore a rather new form of land management, and the demand for 3D property formation has not been as high as initially expected. There is however an increased interest in 3D property and ownership apartments today, also as being part of the nation’s geospatial infrastructure together with related 3D information for e.g. buildings, utility networks and other features. An effective management of 3D property is depending on, among other things, visualization, representation and storage of 3D real property data, such as legal boundaries and real property rights. There are at present a number of ongoing 3D development and research projects focusing on visualization and standardization of 3D cadastral boundaries. They are part of the national "Smart Built Environment" development and research program, which includes the use of BIM in the (future) 3D property formation process with focus on visualization of 3D real property and condominiums, and specification of requirements and evaluation of 3D digital real property information created and managed in the processes.

    This paper presents the preliminary results of the working group on visualization of 3D boundaries in the project "Smart planning, construction and management processes throughout the life cycle". The aim is to test the results produced in the project "Information for planning, real property formation and building permission", working group "BIM for 3D property formation." The purpose of this working group is to set the requirements for and evaluate the test bed for 3D property information. The focus is on visualization of 3D property and ownership apartments. The proposed model for digitization and visualization of 3D property formation will be tested in a test bed environment. A pilot case from the Stockholm area is then used in the test bed to see how it could work in practice.

    The expected outcome is recommendations for the exchange of documentation and other digital information in 3D processes, the visualization of legal boundaries for stakeholders, registration of legal 3D objects in the Swedish national real property register and how to communicate 3D models to right holders/stakeholders for 3D property and condominiums and the property market, as well as suggestions for a homogeneous, effective and digital flow of 3D information to be used by actors and other stakeholders in the property formation, planning and building processes.

  • 3.
    Aslani, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Mesgari, Mohammad Saadi
    Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Faculty of Geodesy and Geomatics Engineering, K.N. Toosi University of Technology, Tehran, Iran.
    Wiering, Marco
    Institute of Artificial Intelligence and Cognitive Engineering, University of Groningen, Groningen, Netherlands.
    Developing adaptive traffic signal control by actor-critic and direct exploration methods2018In: Proceedings of the Institution of Civil Engineers: Transport, ISSN 0965-092X, E-ISSN 1751-7710, article id jtran.17.00085Article in journal (Refereed)
    Abstract [en]

    Designing efficient traffic signal controllers has always been an important concern in traffic engineering. This is owing to the complex and uncertain nature of traffic environments. Within such a context, reinforcement learning has been one of the most successful methods owing to its adaptability and its online learning ability. Reinforcement learning provides traffic signals with the ability automatically to determine the ideal behaviour for achieving their objective (alleviating traffic congestion). In fact, traffic signals based on reinforcement learning are able to learn and react flexibly to different traffic situations without the need of a predefined model of the environment. In this research, the actor-critic method is used for adaptive traffic signal control (ATSC-AC). Actor-critic has the advantages of both actor-only and critic-only methods. One of the most important issues in reinforcement learning is the trade-off between exploration of the traffic environment and exploitation of the knowledge already obtained. In order to tackle this challenge, two direct exploration methods are adapted to traffic signal control and compared with two indirect exploration methods. The results reveal that ATSC-ACs based on direct exploration methods have the best performance and they consistently outperform a fixed-time controller, reducing average travel time by 21%.

  • 4.
    Aslani, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Faculty of Geodesy and Geomatics Engineering, K.N. Toosi University of Technology, Tehran, Iran.
    Mohammad Saadi, Mesgari
    Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Wiering, Marco A.
    Institute of Artificial Intelligence and Cognitive Engineering, University of Groningen, Groningen, Netherlands.
    Traffic signal optimization through discrete and continuous reinforcement learning with robustness analysis in downtown Tehran2018In: Advanced Engineering Informatics, ISSN 1474-0346, E-ISSN 1873-5320, Vol. 38, p. 639-655Article in journal (Refereed)
    Abstract [en]

    Traffic signal control plays a pivotal role in reducing traffic congestion. Traffic signals cannot be adequately controlled with conventional methods due to the high variations and complexity in traffic environments. In recent years, reinforcement learning (RL) has shown great potential for traffic signal control because of its high adaptability, flexibility, and scalability. However, designing RL-embedded traffic signal controllers (RLTSCs) for traffic systems with a high degree of realism is faced with several challenges, among others system disturbances and large state-action spaces are considered in this research.

    The contribution of the present work is founded on three features: (a) evaluating the robustness of different RLTSCs against system disturbances including incidents, jaywalking, and sensor noise, (b) handling a high-dimensional state-action space by both employing different continuous state RL algorithms and reducing the state-action space in order to improve the performance and learning speed of the system, and (c) presenting a detailed empirical study of traffic signals control of downtown Tehran through seven RL algorithms: discrete state Q-learning(λ" role="presentation">), SARSA(λ" role="presentation">), actor-critic(λ" role="presentation">), continuous state Q-learning(λ" role="presentation">), SARSA(λ" role="presentation">), actor-critic(λ" role="presentation">), and residual actor-critic(λ" role="presentation">).

    In this research, first a real-world microscopic traffic simulation of downtown Tehran is carried out, then four experiments are performed in order to find the best RLTSC with convincing robustness and strong performance. The results reveal that the RLTSC based on continuous state actor-critic(λ" role="presentation">) has the best performance. In addition, it is found that the best RLTSC leads to saving average travel time by 22% (at the presence of high system disturbances) when it is compared with an optimized fixed-time controller.

  • 5.
    Aslani, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Wiering, Marco
    Institute of Artificial Intelligence and Cognitive Engineering, University of Groningen, Groningen, the Netherlands.
    Continuous residual reinforcement learning for traffic signal control optimization2018In: Canadian journal of civil engineering (Print), ISSN 0315-1468, E-ISSN 1208-6029, Vol. 45, no 8, p. 690-702Article in journal (Refereed)
    Abstract [en]

    Traffic signal control can be naturally regarded as a reinforcement learning problem. Unfortunately, it is one of the most difficult classes of reinforcement learning problems owing to its large state space. A straightforward approach to address this challenge is to control traffic signals based on continuous reinforcement learning. Although they have been successful in traffic signal control, they may become unstable and fail to converge to near-optimal solutions. We develop adaptive traffic signal controllers based on continuous residual reinforcement learning (CRL-TSC) that is more stable. The effect of three feature functions is empirically investigated in a microscopic traffic simulation. Furthermore, the effects of departing streets, more actions, and the use of the spatial distribution of the vehicles on the performance of CRL-TSCs are assessed. The results show that the best setup of the CRL-TSC leads to saving average travel time by 15% in comparison to an optimized fixed-time controller.

  • 6.
    Ericsson, Martin
    et al.
    Uppsala universitet.
    Hast, Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    A Heterogeneous Cluster framework for Computationally Heavy Visualizations2009In: Proceedings of IADIS Applied Computing 2009, 2009, p. 337-339Conference paper (Refereed)
  • 7.
    Forsberg, Ann-Kristin
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Winkler Pettersson, Lars
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Linden, Elisabet
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    An augmented-reality approach to co-located visual exploration of indoor climate data in real rooms2005In: Indoor Air 2005: Proceedings of the 10th International Conference on Indoor Air Quality and Climate, 2005, p. 2860-2860Conference paper (Other academic)
    Abstract [en]

    We live in two spaces, the visible space and the non-visible but otherwise sensed space. Both spaces must satisfy our needs and there is a relation between them. If parts of the room are too cold this will lead to a restriction of the use of the room. We cannot endure draft for any longer time. Draft caused by a ventilation supply frequently leads to blockage of the supply device, which in turn gives rise to a reduction of the ventilation rate. The final result may be a deterioration of the air quality. Therefore, to be able to guarantee the air quality it is necessary to make the invisible thermal climate visible. In this paper a novel method based on Augmented Reality for presenting die thermal climate is presented and discussed. The data, e.g. temperatures and velocities, are shown on a lightweight display. Several people can walk around in a real room and see on a screen where the hot and/or cold spots may appear. Different ventilation solutions could in that way be compared in a dialogue between different actors in the building process.

  • 8. Forsell, C
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Lind, M
    Simple 3D Glyphs for Spatial Multivariate Data2005In: Proceedings of the IEEE Symposium on Information Visualization – Infovis 2005, 2005, p. 119-124Conference paper (Other academic)
    Abstract [en]

    We present an effort to evaluate the possible utility of a new type of 3D glyphs intended for visualizations of multivariate spatial data. They are based on results from vision research suggesting that our perception of metric 3D structure is distorted and imprecise relative to the actual scene before us (e.g., [1]); only a class of qualitative properties of the scene is perceived with accuracy. These properties are best characterized as being invariant over affine but not Euclidean transformations. They are related, but not identical to, the non-accidental properties (NAPs) described by Lowe [2] on which the notion of geons is based [3]. A large number of possible 3D glyphs for the visualization of spatial data can be constructed using such properties. One group is based on the local sign of surface curvature. We investigated these properties in a visualization experiment. The results are promising and the implications for visualization are discussed.

  • 9. Forsell, C.
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Lind, M.
    Surface Glyphs for Efficient Visualization of Multivariate Data2006In: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 5, no 2, p. 112-124Article in journal (Refereed)
    Abstract [en]

    We present a first effort to evaluate the possible utility of a new type of surface glyphs intended for visualizations of multivariate spatial data. The glyphs are based on results from vision research suggesting that our perception of metric 3D structure is distorted and imprecise relative to the actual scene before us; only a class of qualitative properties of the scene is perceived with accuracy. These properties are best characterized as being invariant over affine but not Euclidean transformations. A large number of possible 3D glyphs for the visualization of spatial data can be constructed using such properties. One group of such glyphs is based on the local sign of surface curvature. We investigated this group in two visualization experiments. The results show that available sources of 3D structural information were sufficient for our subjects to make fast and accurate judgments. Some implications for visualization are also discussed.

  • 10.
    Hast, Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Ericsson, Martin
    UPPMAX, Uppsala University, Uppsala, Sweden .
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Multiscale Texture Synthesis and Colourization of Greyscale Textures2010In: 18th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision, WSCG 2010 - In Co-operation with EUROGRAPHICS: Full Papers Proceedings, Plzen: Union Agency Science Press , 2010, p. 55-61Conference paper (Refereed)
    Abstract [en]

    The main idea presented herein is to use a multiscale texture synthesis approach in order to both colourize and upscale greyscale textures. Such textures can be vintage photos to be used in archaeological or urban 3D visualizations and obviously the colour needs to be reconstructed some way. Due to limited quality, walls etc in such 3D visualizations will appear either pixelized or blurry when the viewer approaches them on a close distance. The latter if some kind of interpolation technique is being used to reduce the pixelization. The low resolution greyscale texture and a high resolution coloured texture is used for the colourization and upscaling, which will produce a colour version of the greyscale texture with 4 times higher resolution in each upscale step. The novel idea is to use multiscale texture synthesis in HSV space for the first upscale in order to create a RGB colour image for subsequent upscaling, using either ordinary RGB multiscale texture synthesis or continue using HSV multiscale texture synthesis. These two main approaches will be compared and discussed.

  • 11.
    Hast, Anders
    et al.
    Uppsala universitet.
    Jenke, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Uppsala universitet.
    Shortest diagonal triangulation of convex layers2013In: Proceedings of the IASTED International Conference on Signal Processing, Pattern Recognition and Applications, SPPRA 2013, 2013, p. 424-430Conference paper (Refereed)
    Abstract [en]

    One problem in the field of computational geometry is the triangulation of convex layers. The rotating caliper algorithm is an alternative to the constrained Delaunay triangulation method. We present an improved triangulation algorithm, which gives a mesh quality close to that of the Constrained Delaunay but substantially faster. Each layer will be connected to the neighboring layer by edges and from the two vertices constituting an edge the proposed algorithm will select the shortest diagonal to its next neighbors in the polygonal chain on the other side, i.e. from the outer layer to the inner layer or vice versa. We discuss quality issues regarding the rotating caliper method and some improvements to it, as well as how a Constrained Delaunay can be efficiently implemented for convex layers.

  • 12.
    Hast, Anders
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Wesslén, Daniel
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Improved Diffuse Anisotropic Shading2004In: Proceedings of the Annual SIGRAD Conference, 2004, p. 57-58Conference paper (Refereed)
  • 13.
    Jenke, Peter
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Hast, Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    On the quality of point-cloud triangulations based on convex hulls2010In: Proceedings of the Annual SIGRAD Conference 2010, 2010, p. 71-76Conference paper (Refereed)
  • 14. Jensen, N
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Nejdl, W
    Olbrich, S
    CoVASE - Collaborative Visualization for Constructivist Learning2003In: Designing for Change in Networked Learning Environments, 2003, p. 249-253Conference paper (Other academic)
    Abstract [en]

    The paper specifies CoVASE, a software for teachers to create and view networked learning environments (VE). Students carry out virtual experiments in CoVASE, at the same time and from different places. They use the same tools and work on the same scientific problems as researchers do. Teachers create a motivating, demanding, and authentic interaction between learners and real-world problems, a premise for constructivist learning (CL). CoVASE generates and displays the result of a numerical simulation in parallel of its progress on distributed 3D graphic viewers, steered by users in real-time. VEs mediate communication between users, deictic elements, and display. Researchers and students have evaluated the predecessors of CoVASE with good results. A field study is planned for 2003.

  • 15. Jensen, N
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    von Voigt, G
    Raasch, S
    Olbrich, S
    Nejdl, W
    Development of a Virtual Laboratory System for Science Education and the Study of Collaborative Action2004In: Proceedings of AACE ED Media Conference 2004, 2004Conference paper (Other academic)
    Abstract [en]

    The paper specifies the development of a toolkit to run synthetic science laboratories. The aim was to facilitate collaborative experimenting for problem-based learning in a virtual lab. The goal was to demonstrate virtual experimenting by use of interactive 3D visualization and simulation. Technology was developed over six years and in part designed in explicit accordance to didactic models. For tests, we built a virtual lab that comprised media tools and complex computer simulations, and we evaluated it with promising results. Students used data from meteorology and experimented together. Generally, they enjoyed using the system and collaborated in a motivated way. We identified which tools they preferred. The paper indicates ways to improve the design of virtual labs by use of our toolkit.

  • 16.
    Kjellin, Andreas
    et al.
    Uppsala University.
    Pettersson, Lars Winkler
    Uppsala university.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Lind, Mats
    Uppsala University.
    Evaluating 2D and 3D Visualizations of Spatiotemporal Information2010In: ACM Transactions on Applied Perception, ISSN 1544-3558, E-ISSN 1544-3965, Vol. 7, no 3, p. 19:1-19:23Article in journal (Refereed)
    Abstract [en]

    Time-varying geospatial data presents some specific challenges for visualization. Here, we report the results of three experiments aiming at evaluating the relative efficiency of three existing visualization techniques for a class of such data. The class chosen was that of object movement, especially the movements of vehicles in a fictitious landscape. Two different tasks were also chosen. One was to predict where three vehicles will meet in the future given a visualization of their past movement history. The second task was to estimate the order in which four vehicles arrived at a specific place. Our results reveal that previous findings had generalized human perception in these situations and that large differences in user efficiency exist for a given task between different types of visualizations depicting the same data. Furthermore, our results are in line with earlier general findings on the nature of human perception of both object shape and scene changes. Finally, the need for new taxonomies of data and tasks based on results from perception research is discussed.

  • 17.
    Kjellin, Andreas
    et al.
    Informationsvetenskap, Uppsala universitet.
    Winkler Pettersson, Lars
    Informationsteknologi, Uppsala universitet.
    Seipel, Stefan
    Informationsvetenskap, Uppsala universitet.
    Lind, Mats
    Informationsvetenskap, Uppsala universitet.
    Different levels of 3D: an evaluation of visualized discrete spatiotemporal data in space-time cubes2010In: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 9, no 2, p. 152-164Article in journal (Refereed)
    Abstract [en]

    New technologies and techniques allow novel kinds of visualizations and different types of 3D visualizations are constantly developed. We propose a categorization of 3D visualizations and, based on this categorization, evaluate two versions of a space-time cube that show discrete spatiotemporal data. The two visualization techniques used are a head-tracked stereoscopic visualization ('strong 3D') and a static monocular visualization ('weak 3D'). In terms of effectiveness and efficiency the weak 3D visualization is as good as the strong 3D and thus the need for advanced 3D visualizations in these kinds of tasks may not be necessary.

  • 18.
    Koch, Sabine
    et al.
    CMD Center for Human - Computer Studies , Uppsala University, Uppsala, Sweden.
    Wagner, Ina-Veronika
    CMD Center for Human - Computer Studies , Uppsala University, Uppsala, Sweden.
    Seipel, Stefan
    CMD Center for Human - Computer Studies , Uppsala University, Uppsala, Sweden.
    Schneider, Werner
    CMD Center for Human - Computer Studies , Uppsala University, Uppsala, Sweden.
    Controlled Diagnosis-Oriented Enhancement of Automatically Segmented Radiographs in Dentistry1998In: Computer Methods and Programs in Biomedicine, ISSN 0169-2607, E-ISSN 1872-7565, Vol. 57, no 1-2, p. 125-131Article in journal (Refereed)
    Abstract [en]

    A method for controlled diagnosis-oriented enhancement of selected regions of interest in intraoral radiographs is presented. Image enhancement is accomplished by adaptive non-linear grey scale transformation depending on the result of objective quality measurement. In order to assure reliable image duality measurement as well as controlled image enhancement, automatic image segmentation is applied to avoid the influence of disturbing factors (e.g. metallic restorations) on quality measurement and image enhancement. Based on existing a-priori knowledge about object structure and composition of the selected regions of interest in intraoral radiographs, different image segmentation algorithms and image enhancement procedures were developed for different types of diagnosis. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.

  • 19. Kordaß, B.
    et al.
    Gärtner, Ch.
    Söhnel, A.
    Bisler, A.
    Voß, G.
    Bockholt, U.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    The virtual articulator in dentistry: concept and development2002In: Dental Clinics of North America, ISSN 1558-0512, Vol. 46, no 3, p. 493-506Article in journal (Refereed)
    Abstract [en]

    Virtual Reality (VR) technology is one of the most important innovations for research, development, and industrial production. In dentistry, VR technology will be useful in providing better education through simulation and in enhancing working procedures that are conventionally limited, e.g., the mechanical articulator. It is the purpose of this article to present concepts and strategies for a future replacement of the mechanical articulator by a virtual one.

  • 20.
    Lim, Nancy J.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Assessment of spatial-based decisions and user perspectives in utilisation of flood certainty mapsManuscript (preprint) (Other academic)
  • 21.
    Lim, Nancy Joy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Visualisation and evaluation of flood uncertainties based on ensemble modelling2016In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 30, no 2, p. 240-262Article in journal (Refereed)
    Abstract [en]

    This study evaluates how users incorporate visualisation of flood uncertainty information in decision-making. An experiment was conducted where participants were given the task to decide building locations, taking into account homeowners’ preferences as well as dilemmas imposed by flood risks at the site. Two general types of visualisations for presenting uncertainties from ensemble modelling were evaluated: (1) uncertainty maps, which used aggregated ensemble results; and (2) performance bars showing all individual simulation outputs from the ensemble. Both were supplemented with either two-dimensional (2D) or three-dimensional (3D) contextual information, to give an overview of the area.The results showed that the type of uncertainty visualisation was highly influential on users’ decisions, whereas the representation of the contextual information (2D or 3D) was not. Visualisation with performance bars was more intuitive and effective for the task performed than the uncertainty map. It clearly affected users’ decisions in avoiding certain-to-be-flooded areas. Patterns to which the distances were decided from the homeowners’ preferred positions and the uncertainties were similar, when the 2D and 3D map models were used side by side with the uncertainty map. On the other hand, contextual information affected the time to solve the task. With the 3D map, it took the participants longer time to decide the locations, compared with the other combinations using the 2D model.Designing the visualisation so as to provide more detailed information made respondents avoid dangerous decisions. This has also led to less variation in their overall responses.

  • 22.
    Lim, Nancy Joy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Åhlén, Julia
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Geovisualisation of uncertainty in simulated flood maps2014In: Proceedings of the International Conferences on Interfaces and Human Computer Interaction 2014, Game and Entertainment Technologies 2014 and Computer Graphics, Visualization, Computer Vision and Image Processing 2014 - Part of the Multi Conference on Computer Science and Information Systems, MCCSIS 2014 / [ed] Katherine Blashki and Yingcai Xiao, IADIS Press , 2014, p. 206-214Conference paper (Refereed)
    Abstract [en]

    The paper presents a three-dimensional (3D) geovisualisation model of uncertainties in simulated flood maps that can help communicate uncertain information in the data being used. An entropy-based measure was employed for uncertainty quantification. In developing the model, Visualisation Toolkit (VTK) was utilised. Different data derived from earlier simulation study and other maps were represented in the model. Cartographic principles were considered in the map design. A Graphical User Interface (GUI), which was developed in Tkinter, was also created to further support exploratory data analysis. The resulting model allowed visual identification of uncertain areas, as well as displaying spatial relationship between the entropy and the slope values. This geovisualisation has still to be tested to assess its effectiveness as a communication tool. However, this type of uncertainty visualisation in flood mapping is an initial step that can lead to its adoption in decision-making when presented comprehensively to its users. Thus, further improvement and development is still suggested for this kind of information presentation.

  • 23. Lind, M.
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Mattiason, C.
    Displaying meta-information in context2001In: Behavior and Information Technology, ISSN 0144-929X, E-ISSN 1362-3001, Vol. 20, no 6, p. 427-432Article in journal (Refereed)
    Abstract [en]

    Very often information exists that would be helpful for process control operators if it could be presented in the context they work in-the process graphics. Examples are instructional material, visualizations of automated sequences, output from knowledge-based systems or simply annotations that one team of operators wants to communicate with another. Several existing distortion techniques were reviewed that would allow the ordinary process graphics to take less space leaving room for additional information. However, these techniques were rejected, mainly because all parts of a process control screen need to be readable at all times. A new technique is proposed and its readability experimentally evaluated with promising results.

  • 24.
    Liu, Fei
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Detection of Façade Regions in Street View Images from Split-and-Merge of Perspective Patches2014In: Journal of Image and Graphics, ISSN ISSN 2301-3699, Vol. 2, no 1, p. 8-14Article in journal (Refereed)
    Abstract [en]

    Identification of building façades from digital images is one of the central problems in mobile augmented reality (MAR) applications in the built environment. Directly analyzing the whole image can increase the difficulty of façade identification due to the presence of image portions which are not façade. This paper presents an automatic approach to façade region detection given a single street view image as a pre-processing step to subsequent steps of façade identification. We devise a coarse façade region detection method based on the observation that façades are image regions with repetitive patterns containing a large amount of vertical and horizontal line segments. Firstly, scan lines are constructed from vanishing points and center points of image line segments. Hue profiles along these lines are then analyzed and used to decompose the image into rectilinear patches with similar repetitive patterns. Finally, patches are merged into larger coherent regions and the main building façade region is chosen based on the occurrence of horizontal and vertical line segments within each of the merged regions. A validation of our method showed that on average façade regions are detected in conformity with manually segmented images as ground truth.

  • 25.
    Liu, Fei
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Detection of Line Features in Digital Images of Building Structures2012In: Proceedings of IADIS International Conference Computer Graphics, Visualization, Computer Vision and Image Processing 2012 (CGVCVIP 2012) / [ed] Yingcai Xiao, 2012, p. 163-167Conference paper (Refereed)
    Abstract [en]

    This paper describes method for detection of short line segments in digital images. It aims at identifying buildingsin images taken from the ground view. The process starts with the image edge map and is carried out in twodifferent levels. One is to detect long line segments usually stemming from façade edges and building silhouettes.The other one identifies shorter line segments which typically represent architectural details such as windows andentrances. Selected individual connected components in both vertical and horizontal gradient component mapsare used respectively as input to the Hough transform at this level. Our first result shows that this method iscapable of recognizing lines of interest but has also included many randomly oriented lines. The next step will beto eliminate the random line segments and correlate line segments of the two levels to classify high-level features ofbuildings in an image.

  • 26.
    Liu, Fei
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
    Infrared-visible image registration for augmented reality-based thermographic building diagnostics2015In: Visualization in Engineering, ISSN 2213-7459, Vol. 3, no 1, article id 16Article in journal (Refereed)
    Abstract [en]

    Background: In virtue of their capability to measure temperature, thermal infrared cameras have been widely used in building diagnostics for detecting heat loss, air leakage, water damage etc. However, the lack of visual details in thermal infrared images makes the complement of visible images a necessity. Therefore, it is often useful to register images of these two modalities for further inspection of architectures. Augmented reality (AR) technology, which supplements the real world with virtual objects, offers an ideal tool for presenting the combined results of thermal infrared and visible images. This paper addresses the problem of registering thermal infrared and visible façade images, which is essential towards developing an AR-based building diagnostics application. Methods: A novel quadrilateral feature is devised for this task, which models the shapes of commonly present façade elements, such as windows. The features result from grouping edge line segments with the help of image perspective information, namely, vanishing points. Our method adopts a forward selection algorithm to determine feature correspondences needed for estimating the transformation model. During the formation of the feature correspondence set, the correctness of selected feature correspondences at each step is verified by the quality of the resulting registration, which is based on the ratio of areas between the transformed features and the reference features. Results and conclusions: Quantitative evaluation of our method shows that registration errors are lower than errors reported in similar studies and registration performance is usable for most tasks in thermographic inspection of building façades.

  • 27.
    Liu, Fei
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University.
    On the precision of third person perspective augmented reality for target designation tasks2017In: Multimedia tools and applications, ISSN 1380-7501, E-ISSN 1573-7721, Vol. 76, no 14, p. 15279-15296Article in journal (Refereed)
    Abstract [en]

    The availability of powerful consumer-level smart devices and off-the-shelf software frameworks has tremendously popularized augmented reality (AR) applications. However, since the built-in cameras typically have rather limited field of view, it is usually preferable to position AR tools built upon these devices at a distance when large objects need to be tracked for augmentation. This arrangement makes it difficult or even impossible to physically interact with the augmented object. One solution is to adopt third person perspective (TPP) with which the smart device shows in real time the object to be interacted with, the AR information and the user herself, all captured by a remote camera. Through mental transformation between the user-centric coordinate space and the coordinate system of the remote camera, the user can directly interact with objects in the real world. To evaluate user performance under this cognitively demanding situation, we developed such an experimental TPP AR system and conducted experiments which required subjects to make markings on a whiteboard according to virtual marks displayed by the AR system. The same markings were also made manually with a ruler. We measured the precision of the markings as well as the time to accomplish the task. Our results show that although the AR approach was on average around half a centimeter less precise than the manual measurement, it was approximately three times as fast as the manual counterpart. Additionally, we also found that subjects could quickly adapt to the mental transformation between the two coordinate systems.

  • 28.
    Liu, Fei
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
    Precision study on augmented reality-based visual guidance for facility management tasks2018In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 90, p. 79-90Article in journal (Refereed)
    Abstract [en]

    One unique capability of augmented reality (AR) is to visualize hidden objects as a virtual overlay on real occluding objects. This “X-ray vision” visualization metaphor has proved to be invaluable for operation and maintenance tasks such as locating utilities behind a wall. Locating virtual occluded objects requires users to estimate the closest projected positions of the virtual objects upon their real occluders, which is generally under the influence of a parallax effect. In this paper we studied the task of locating virtual pipes behind a real wall with “X-ray vision” and the goal is to establish relationships between task performance and spatial factors causing parallax through different forms of visual augmentation. We introduced and validated a laser-based target designation method which is generally useful for AR-based interaction with augmented objects beyond arm's reach. The main findings include that people can mentally compensate for the parallax error when extrapolating positions of virtual objects on the real surface given traditional 3D depth cues for spatial understanding. This capability is, however, unreliable especially in the presence of the increasing viewing offset between the users and the virtual objects as well as the increasing distance between the virtual objects and their occluders. Experiment results also show that positioning performance is greatly increased and unaffected by those factors if the AR support provides visual guides indicating the closest projected positions of virtual objects on the surfaces of their real occluders.

  • 29.
    Milutinovic, Goran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Ahonen-Jonnarth, Ulla
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Decision, Risk and Policy Analysis.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Department of Information Technology, Uppsala University, Uppsala, Sweden.
    GISwaps: A New Method for Decision Making in Continuous Choice Models Based on Even Swaps2018In: International Journal of Decision Support System Technology, ISSN 1941-6296, E-ISSN 1941-630X, Vol. 10, no 3, p. 57-78Article in journal (Refereed)
    Abstract [en]

    This article describes how continuous GIS-MCDM problems are commonly managed by combining some weighting method based on pairwise comparisons of criteria with an aggregation method. The reliability of this approach may be questioned, though. First, assigning weights to criteria, without taking into consideration the actual consequences or values of the alternatives, is in itself controversial. Second, the value functions obtained by this approach are in most cases linear, which is seldom the case in reality. The authors present a new method for GIS-MCDM in continuous choice models based on Even Swaps. The method is intuitive and easy to use, based on value trade-offs, and thus not relying on criteria weighting. Value functions obtained when using the method may be linear or non-linear, and thereby are more sensitive to the characteristics of the decision space. The performed case study showed promising results regarding the reliability of the method in GIS-MCDM context.

  • 30.
    Milutinovic, Goran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Ahonen-Jonnarth, Ulla
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Decision, Risk and Policy Analysis.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science. Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    The impact of interactive visualization on trade-off-based geospatial decision-making2019In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 33, no 10, p. 2094-2123Article in journal (Refereed)
    Abstract [en]

    In a previous work we developed GISwaps, a novel method for geospatial decision-making based on Even Swaps. In this paper, we present the results of an evaluation of a visualization framework integrated with this method, implemented within a decision support system. This evaluation is based on two different studies. In the quantitative study, 15 student participants used GISwaps with no visual features, and 15 participants used GISwaps with the integrated visual framework, as the tool in a solar farm site location case study. The results of the quantitative evaluation show positive impact of the visualization in terms of increased coherency in trade-offs. The results also show a statistically significant difference in average trade-off values between the groups, with users from the non-visual group setting on average 20% higher trade-off values compared with the users in the visual group. In the qualitative study, we had one expert in GIS, two experts in decision-making and two experts in solar energy as a focus user group. Data in this study were obtained by observations and semi-structured interviews with the participants. The impact of the visualization framework was assessed positively by all participants in the expert group. 

  • 31.
    Milutinovic, Goran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Visual GISwaps - an interactive visualization framework for geospatial decision making2018In: Proceedings of the 13th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications, VISIGRAPP 2018, Funchal, Madeira - Portugal, January 27-29, 2018 / [ed] Alexandru Telea, Andreas Kerren and Jose Braz, SciTePress, 2018, p. 236-243Conference paper (Refereed)
    Abstract [en]

    Different visualization techniques are frequently used in geospatial information systems (GIS) to support geospatial decision making. However, visualization in GIS context is usually limited to the initial phase of the decision-making process, i.e. situation analysis and problem recognition. This is partly due to the choice of methods used in GIS multi-criteria decision-making (GIS-MCDM) that usually deploy some non-interactive approach, leaving the decision maker little or no control over the calculation of overall values for the considered alternatives; the role of visualization is thus reduced to presenting the final results of the computations. The contributions of this paper are twofold. First, we introduce GISwaps, a novel, intuitive interactive method for decision making in geospatial context. The second and main contribution is an interactive visualization of the choice phase of the decision making process. The visualization allows the decision maker to explore the consequences of trade-offs and costs accepted during the iterative decision process, both in terms of the abstract relation between different decision variables and in spatial context.

  • 32. Nyström, Ingela
    et al.
    Olsson, Pontus
    Nysjö, Johan
    Nysjö, Fredrik
    Malmberg, Filip
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Hirsch, Jan-Michel
    Carlbom, Ingrid B.
    Virtual Cranio-Maxillofacial Surgery Planning with Stereo Graphics and Haptics2016In: Computer-Assisted Musculoskeletal Surgery: Thinking and Executing in 3D / [ed] Ritacco, L .E. and Milano, F. E. and Chao, E., Springer Publishing Company, 2016, 1, p. 29-42Chapter in book (Refereed)
  • 33.
    Ohlsson, P
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Real-time Rendering of Accumulated Snow2004In: Proceedings of the Annual SIGRAD Conference, 2004, p. 25-32Conference paper (Other academic)
  • 34. Olsson, E
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Jansson, A
    Safer navigation at sea using augmented reality2002In: Proceedings of HCI'02, People and Computers, 2002, p. 154-157Conference paper (Other academic)
  • 35.
    Olsson, Pontus
    et al.
    Uppsala University, Uppsala, Sweden.
    Nysjö, Fredrik
    Uppsala University, Uppsala, Sweden.
    Aneer, Björn
    Independent Artist, Stockholm, Sweden .
    Seipel, Stefan
    Uppsala University, Uppsala, Sweden.
    Carlbom, Ingrid
    Uppsala University, Uppsala, Sweden.
    SplineGrip - An eight degrees-of-freedom flexible haptic sculpting tool2013In: Proceeding SIGGRAPH '13 ACM SIGGRAPH 2013 Posters, 2013Conference paper (Refereed)
    Abstract [en]

    Haptic sculpting allows a designer to create virtual models with the aid of haptic feedback. Just as in real life sculpting, different tools are used to work the model into a desired shape. Several haptic sculpting tools appear in the literature. For example, [Gao 2006] proposes an ellipsoidal tool whose pose (position and orientation) is controlled by a six degrees-of-freedom (DOF) haptic device, and [McDonnell 2001] describes a set of modeling tools for virtual clay controlled by three DOF haptics.

  • 36.
    Olsson, Pontus
    et al.
    Uppsala universitet, Informationsteknologi.
    Nysjö, Fredrik
    Uppsala universitet, Informationsteknologi.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Carlbom, Ingrid
    Uppsala universitet, Informationsteknologi.
    Physically Co-Located Haptic Interaction with 3D Displays2012In: Proc. Haptics Symposium (HAPTICS), 2012 IEEE, 2012, p. 267-272Conference paper (Refereed)
    Abstract [en]

    Studies indicate that haptic interaction with a computer generated virtual scene may become more intuitive by aligning (co-locating) the visual and haptic workspaces so that the visual and haptic feedback coincide as they do in the real world. Co-located haptics may gain importance when more advanced haptic interfaces, such as high-fidelity whole hand devices, become available. We describe a user study that investigates the pros and cons with physically co-located versus non-collocated haptics on two different display types: a commercial half-transparent mirror 3D display with shutter glasses and a prototype autostereoscopic display based on a Holographic Optical Element (HOE). We use two accuracy tasks with spatial accuracy as the dependent variable and one manipulation task with time as the dependent variable. The study shows that on both displays co-location significantly improves completion time in the manipulation task. However, the study shows that co-location does not improve the accuracy in the spatial accuracy tasks.

  • 37.
    Ooms, Kristien
    et al.
    Department of Geography, Ghent University, Ghent, Belgium.
    Åhlén, Julia
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Detecting Collapsed Buildings in Case of Disaster: Which Visualisation Works Best?2018In: Eye Tracking for Spatial Research: Proceedings of the 3rd International Workshop / [ed] Kiefer, Peter Giannopoulos, Ioannis Göbel, Fabian Raubal, Martin Duchowski, Andrew T., Zurich, 2018Conference paper (Refereed)
    Abstract [en]

    A user study is conducted to evaluate the efficiency and effectiveness of two types of visualizations to identify damage sites in case of disaster. The test consists out 36 trials (18 for each visualisation) and in each trial an area of 1x1km, located in Ghent, is displayed on a screen. This image shows the combined height information from before and after the disaster. The first visualisation, page flipping, is based on greyscale images with height information from the pre- and post-disaster situation between which users can switch manually. The second visualisation, difference image, is a result of subtracting the heights (before versus after) and assigning a blue-white-red colour ramp. In order to simulate the urgency with which the data is captured, systematic and random imperfections are introduced in the post-disaster data. All participants’ mouse and key interactions are logged, which is further complemented by the registration of their eye movements. This give insights the visualizations’ efficiency, effectiveness and the overall search strategies of the participants.

  • 38.
    Ooms, Kristien
    et al.
    Department of Geography, Ghent University, Ghent, Belgium.
    Åhlén, Julia
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Efficiency and effectiveness in case of disaster: a visual damage assessment test2018In: Proceedings of the International Cartographic Association (Proceedings of the ICA), 2018, Vol. 1, article id 86Conference paper (Refereed)
    Abstract [en]

     A user study is conducted to evaluate the efficiency and effectiveness of two types of visualizations to identify damages sites in case of disaster. The test consists out 36 trials (18 for each visualisation) and in each trial an area of 1×1km, located in Ghent, is displayed on a screen. This image shows the combined height information from before and after the disaster. The first visualisation, page flipping, is based on greyscale images with height information from the pre- and post-disaster situation between which users can switch manually. The second visualisation, difference image, is a result of subtracting the heights (before versus after) and assigning a blue-white-red colour ramp. In order to simulate the urgency with which the data is captured, systematic and random imperfections are introduced in the post-disaster data. All participants’ mouse and key interactions are logged, which is further complemented by the registration of their eye movements. This give insights the visualizations’ efficiency, effectiveness and the overall search strategies of the participants.

  • 39. Pettersson, L W
    et al.
    Jemsen, N
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    A Virtual Laboratory for Computer Graphics Education2003In: Proceedings of EUROGRAPHICS Conference 2003, Granada, Spain. 1-6 September 2003, 2003, p. 17-21Conference paper (Other academic)
  • 40. Pettersson, L W
    et al.
    Kjellin, A
    Lind, M
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Effects of layer partitioning in collaborative 3D visualizations2006In: Advances in Visual Computing: Second International Symposium, ISVC 2006 Lake Tahoe, NV, USA, November 6-8, 2006 Proceedings, Part I, Berlin, Heidelberg: Springer , 2006, p. 180-190Conference paper (Other academic)
    Abstract [en]

    Display technologies that support multiple independent views of the same co-located 3D visualization volume make new forms of collaboration possible. In this field of research, until now most efforts have focused on technical solutions and their applications. The main contribution of this paper is the results from a study comparing integral and partitioned 3D content in a head coupled stereoscopic environment through independent views of a shared 3D visualization.

    In our study we used a geospatial task that was solved by ten pairs of collaborating individuals (dyads). We measured task performance by time and error rate for the dyads in two main conditions: a) an integral visualization that presented a map in the display surface and four layers at different depths below the display surface to each of the observers, and b) a partitioned visualization, where two mutually exclusive subsets of the layers were presented to each of the observers together with the map in the display surface.

    The results from the study showed significant differences in regard to performance times between the two conditions. Task performance was significantly better in the condition with layer partitioning. Partitioned visualizations can thus, at least in some cases, improve performance in tasks requiring collaboration between users.

  • 41. Pettersson, L W
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Collaborative 3D Visualizations of Geo-Spatial Information for Command and Control2004In: Proceedings of the Annual SIGRAD Conference, 2004, p. 41-47Conference paper (Other academic)
  • 42. Pettersson, L W
    et al.
    Wesslén, Daniel
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    In situ tomographic display for interactive data visualization2004In: Proceedings of the third Nordic conference on Human-Computer Interaction, 2004Conference paper (Other academic)
    Abstract [en]

    With tomographic in situ visualization we present a novel approach to interactive data visualization and exploration. This visualization concept is useful for presentation of spatially co-located information that is normally not visible to the human's eye. The tomographic in situ display allows for interactive cutting through data in space by using a spatially tracked and calibrated display. In this paper we describe the technical apparatus of our prototype and describe an application for the tomographic in situ visualization in the field of indoor climate studies.

  • 43. Pettersson, Lars Winkler
    et al.
    Lind, M
    Spak, Ulrik
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Visualization of symbols in a horizontal multiple viewer 3D display environment2005In: Proceedings of IEEE Information Visualization 2005, 2005, p. 357-362Conference paper (Other academic)
    Abstract [en]

    In this paper we present a visualization environment for collaborative and co-located displays of geospatially related data for command and control. We first describe the working principle of a novel horizontal display that is aimed at providing high resolution stereoscopic 3D visualizations simultaneously to a group of up to four observers. This display environment opens up new ways to present view-dependent visual content within a shared workspace. For this environment we propose frontoparallel presentations of conventional symbols that are 3D presentations of 2D symbols which appear virtually oriented towards the line of sight of the observer. In an experiment we compare frontoparallel symbols with flat symbols i.e. symbols that are presented in the horizontal plane of the display. The results of our study indicate that frontoparallel symbols in a stereoscopic view are perceived and identified faster than symbols presented flat in relation to the plane of the display.

  • 44.
    Ren, Zheng
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Jiang, Bin
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Capturing and characterizing human activities using building locations in America2019In: ISPRS International Journal of Geo-Information, ISSN 2220-9964, Vol. 8, no 5, article id 200Article in journal (Refereed)
    Abstract [en]

    Capturing and characterizing collective human activities in a geographic space have become much easier than ever before in the big era. In the past few decades it has been difficult to acquire the spatiotemporal information of human beings. Thanks to the boom in the use of mobile devices integrated with positioning systems and location-based social media data, we can easily acquire the spatial and temporal information of social media users. Previous studies have successfully used street nodes and geo-tagged social media such as Twitter to predict users’ activities. However, whether human activities can be well represented by social media data remains uncertain. On the other hand, buildings or architectures are permanent and reliable representations of human activities collectively through historical footprints. This study aims to use the big data of US building footprints to investigate the reliability of social media users for human activity prediction. We created spatial clusters from 125 million buildings and 1.48 million Twitter points in the US. We further examined and compared the spatial and statistical distribution of clusters at both country and city levels. The result of this study shows that both building and Twitter data spatial clusters show the scaling pattern measured by the scale of spatial clusters, respectively, characterized by the number points inside clusters and the area of clusters. More specifically, at the country level, the statistical distribution of the building spatial clusters fits power law distribution. Inside the four largest cities, the hotspots are power-law-distributed with the power law exponent around 2.0, meaning that they also follow the Zipf’s law. The correlations between the number of buildings and the number of tweets are very plausible, with the r square ranging from 0.53 to 0.74. The high correlation and the similarity of two datasets in terms of spatial and statistical distribution suggest that, although social media users are only a proportion of the entire population, the spatial clusters from geographical big data is a good and accurate representation of overall human activities. This study also indicates that using an improved method for spatial clustering is more suitable for big data analysis than the conventional clustering methods based on Euclidean geometry.

  • 45.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Centre of Image Analysis, Uppsala University, Uppsala, Sweden.
    Evaluating 2D and 3D Geovisualizations for Basic Spatial Assessment2013In: Behavior and Information Technology, ISSN 0144-929X, E-ISSN 1362-3001, Vol. 32, no 8, p. 845-858Article in journal (Refereed)
    Abstract [en]

    This study investigates the use of 2D and 3D presentations of maps for the assessment of distances in a geographicalcontext. Different types of 3D representations have been studied: A weak 3D visualisation that provides staticmonocular depth cues and a strong 3D visualisation that uses stereoscopic and kinetic depth cues. Two controlledexperiments were conducted to test hypotheses regarding subjects’ efficiency in visually identifying the shortestdistance among a set of market locations in a map. As a general result, we found that participants were able tocorrectly identify shortest distances when the difference to potential alternatives was sufficiently large, butperformance decreased systematically when this difference decreased. Noticeable differences emerged for theinvestigated visualisation conditions. Participants in this study were equally efficient when using a weak 3Drepresentation and a 2D representation. When the strong 3D visualisation was employed, they reported visualdiscomfort and tasks were solved significantly less correct. Presentations of intrinsic 2D content (maps) in 3Dcontext did, in this study, not benefit from cues provided by a strong 3D visualisation and are adequatelyimplemented using a weak 3D visualisation.

  • 46.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Information Visualization using Transparent Shape Impostors2003In: Proceedings of EUROGRAPHICS Conference 2003, 2003, p. 249-254Conference paper (Other academic)
    Abstract [en]

    Transparency is a graphical effect used in visualizations to present co-located graphical glyphs. Accomplishinga visually convincing transparency effect requires complex calculations of light absorption andrefraction in object space. Alternatively, screen-space sorted rendering of graphical primitives using colour-blending techniques can be used for interactive applications. In this paper an efficient way is presentedto render transparent glyphs for information visualization. The technique combines random dotsurface plots with pre-computed transparent shape impostors to present different levels of transparencyfor co-located graphical glyphs. It is shown that this rendering method is faster than ordered polygonrendering using blending.

  • 47.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Uppsala universitet.
    Solving Geospatial Tasks in 2D and 3D Visualisation of Maps2014In: Information Visualisation: Techniques, Usability and Evaluation / [ed] Ebad Banissi, Francis T. Marchese, Camilla Forsell and Jimmy Johansson, Newcastle upon Tyne: Cambridge Scholars Publishing, 2014, 1, p. 222-271Chapter in book (Refereed)
  • 48.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Telematic dental articulation system for remote teaching in collaborative virtual Telemedicine2001In: Abstracts of the 6th International Conference on the Medical Aspects of Telemedicine, 2001Conference paper (Other academic)
  • 49.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Volumetric Normal Mapping in Rendering of Multivariate Volume Data2007In: Proceedings of Eurographics 2007 - Shortpapers and Medical Prices, Prague, September 3-7, 2007, p. 49-52Conference paper (Refereed)
  • 50.
    Seipel, Stefan
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Ahreberg, L
    Distributed Rendering in Heterogeneous Display Environments: A Functional Framework Design and Performan Assessment2002In: Proceedings of the Annual SIGRAD Conference, 2002, p. 23-28Conference paper (Other academic)
12 1 - 50 of 84
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf