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Unravelling the Human Perspective and Considerations for Urban Data Visualization

14th IEEE Pacific Visualization Symposium (PacificVis), 126-130. DOI:10.1109/PacificVis52677.2021.00024, 04/2021
Sarah Goodwin Sebastian Meier Alex Godwin Lyn Bartram Till Nagel Marian Dörk

Effective use of data is an essential asset to modern cities. Visualization as a tool for analysis, exploration, and communication has become a driving force in the task of unravelling our complex urban fabrics. This paper outlines the findings from a series of three workshops from 2018-2020 bringing together experts in urban data visualization with the aim of exploring multidisciplinary perspectives from the human-centric lens. Based on the rich and detailed workshop discussions identifying challenges and opportunities for urban data visualization research, we outline major human-centric themes and considerations fundamental for CityVis design and introduce a framework for an urban visualization design space.

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A visual approach for analyzing readmissions in intensive care medicine

Visual Analytics in Healthcare Workshop (VAHC 2020), AMIA Annual Symposium, 24-25, DOI:10.1109/VAHC53729.2020.00010, 01/2021
Jan Scheer Till Nagel Thomas Ganslandt

Intensive care units (ICUs) are under constant pressure to balance capacity. ICUs have a limited number of resources and therefore effective monitoring of planned and unplanned transfers is crucial. Transfers can result in critical readmissions, i.e. “down” transfers from ICUs to a normal ward or an intermediate care unit (IMC) and back “up” to an ICU within a short time span. In this work, we present a tool to visually analyze critical ICU readmissions. Patient transfer data is extracted from a clinical data warehouse via HL7-FHIR. The interactive prototype consists of a timeline of readmission cases, an aggregated view of transfer flows between wards, and histograms and calender heatmaps to show a set of key performance indicators. The aim of our tool is to support identifying peaks, discovering temporal patterns, comparing wards, and investigating potential causes. We report on our user centered approach, describe the data pipeline, present the visualization and interaction techniques of the functional prototype, and discuss initial feedback.


Understanding User Experience of COVID-19 Maps through Remote Elicitation Interviews

IEEE Workshop on Evaluation and Beyond - Methodological Approaches to Visualization (BELIV), 65–73, 06/2020
Damla Çay Till Nagel Asım Evren Yantaç

During the coronavirus pandemic, visualizations gained a new level of popularity and meaning for a wider audience. People were bombarded with a wide set of public health visualizations ranging from simple graphs to complex interactive dashboards. In a pandemic setting, where large amounts of the world population are socially distancing themselves, it becomes an urgent need to refine existing user experience evaluation methods for remote settings to understand how people make sense out of COVID-19 related visualizations. When evaluating visualizations aimed towards the general public with vastly different socio-demographic backgrounds and varying levels of technical savviness and data literacy, it is important to understand user feedback beyond aspects such as speed, task accuracy, or usability problems. As a part of this wider evaluation perspective, micro-phenomenology has been used to evaluate static and narrative visualizations to reveal the lived experience in a detailed way. Building upon these studies, we conducted a user study to understand how to employ Elicitation (aka Micro-phenomenological) interviews in remote settings. In a case study, we investigated what experiences the participants had with map-based interactive visualizations. Our findings reveal positive and negative aspects of conducting Elicitation interviews remotely. Our results can inform the process of planning and executing remote Elicitation interviews to evaluate interactive visualizations. In addition, we share recommendations regarding visualization techniques and interaction design about public health data.


ColVis: Collaborative Visualization Design Workshops for Diverse User Groups

Proceedings of the 24th International Conference Information Visualisation (IV), 547–555, 06/2020
Damla Çay Till Nagel Asım Evren Yantaç

Understanding different types of users’ needs can even be more critical in today’s data visualization field, as exploratory visualizations for novice users are becoming more widespread with an increasing amount of data sources. The complexity of data-driven projects requires input from including interdisciplinary expert and novice users. Our workshop framework helps taking design decisions collaboratively with experts and novice users, on different levels such as outlining users and goals, identifying tasks, structuring data, and creating data visualization ideas. We conducted workshops for two different data visualization projects. For each project, we conducted a workshop with project stakeholders who are domain experts, then a second workshop with novice users. We collected feedback from participants and used critical reflection on the process. Later on, we created recommendations on how this workshop structure can be used by others. Our main contributions are, (1) the workshop framework for designing data visualizations, (2) describing the outcomes and lessons learned from multiple workshops.


Visually analysing urban mobility: Results and insights from three student research projects

KN - Journal of Cartography and Geographic Information, 70(1), 11–18, 03/2020
Till Nagel

Since the digitalization of urban mobility, such systems generate large and heterogenous data sets. Handling these, however, is still a major challenge. To help people making sense of urban data, skills in data literacy are needed. In this paper, we present results and insights from a set of mobility visualization projects, students from computer science and design developed over one semester. The resulting prototypes visualize (a) user-generated bike trajectories, (b) population movement, and (c) public transit passengers. After a brief justification on why we find urban mobility a practical domain for teaching data literacy, we introduce the course and describe its set and setting. For each project, we report on the challenge, the data, the visualization prototype, and the impact these projects had. Our contribution is twofold: in the description of the problem-oriented course and its results, and in the reflection of our approach and our lessons learnt.


What is happening in the city? A case study for user-centred geovisualisation design

Journal of Location Based Services (13:4), 270-292, 07/2019
Damla Çay Till Nagel Asım Evren Yantaç

For citizens, being aware of what is happening in their urban surroundings becomes challenging as more information from diverse sources becomes available. In this paper, we describe our user-centered approach of designing an interactive tool making use of urban data visualisations to facilitate people’s decisions about social and cultural events. After gathering the needs of urban actors through formative user studies, we identified beneficial data types and collected a variety of data sets from publicly accessible online sources. For the aim of enabling casual exploration of events in the city, we designed a set of geovisualisation prototypes and designed a variety of evaluative user studies based on established geovisualisation techniques. The main aim here is to enable casual exploration of events in the city more than the intended search for specific events. We developed two prototypes that make use of two different geovisualisations to represent events: Prototype A uses common location markers, and prototype B uses a novel glyph design to visualize more types of data at a glance. We share the lessons learned from the results of our study, which will inform the design of geographical data visualisations for citizens.


Environmental Art as Physicalization Technique

In: Alexander, J. et al (Eds.). Data Physicalization (Dagstuhl Seminar 18441), Dagstuhl Reports, Volume 8, Issue 10, 2019, 03/2019
Till Nagel Laura Perovich Dietmar Offenhuber

Data physicalization involves representing numbers and relationships using physical, tangible displays. These displays provide tactile, as well as visual metaphors for expressing and experiencing data, and can unlock new analytical insights and emotional responses. This Dagstuhl seminar brought together a diverse group of researchers and practitioners to explore the benefits and challenges of physicalization.


ViaVelox - A system to visually analyze GPS-tracked bike rides

Poster Abstracts of IEEE VIS 2018, 10/2018
Deniz Kaya Büsra Keles Dimitry Nagorny Pascal Perle Philip Pregler Lisa Rudolf Martin Schröder Ugur Tunali Till Nagel

This paper presents Via Velox, a system visualizing rides tracked and shared by cyclists through a mobile app. It shows a map and a calendar view side by side, and enables to interactively filter spatial and temporal properties of the rides to allow analyzing bicycle traffic. We explain the functionality of the prototype, and briefly discuss some of the insights people had while using the system at a bicycle festival.

Project Paper Poster Website

What We Learned Through User-Centred Evaluation of Geovisualizations

Proceedings of the CityVis Workshop at the IEEE VIS 2018, 10/2018
Damla Çay Asım Evren Yantaç Till Nagel

Similar to any other design domain, evaluation is an essential phase in the user-centered design process of geo-visualization tools. Different types of evaluation methods can be insightful for different phases of the design process. In this study, we share lessons learned about the evaluation methods employed during the design process of an urban data visualization that facilitates citizens’ decisions on urban socio-cultural events.


Shifted Maps: Revealing spatio-temporal topologies in movement data

Proceedings of the IEEE VIS Arts Program (VISAP), 10/2018
Heike Otten Lennart Hildebrandt Till Nagel Marian Dörk Boris Müller

We present a hybrid visualization technique that integrates maps into network visualizations to reveal and analyze diverse topologies in geospatial movement data. With the rise of GPS tracking in various contexts such as smartphones and vehicles there has been a drastic increase in geospatial data being collect for personal reflection and organizational optimization. The generated movement datasets contain both geographical and temporal information, from which rich relational information can be derived. Common map visualizations perform especially well in revealing basic spatial patterns, but pay less attention to more nuanced relational properties. In contrast, network visualizations represent the specific topological structure of a dataset through the visual connections of nodes and their positioning. So far there has been relatively little research on combining these two approaches. Shifted Maps aims to bring maps and network visualizations together as equals. The visualization of places shown as circular map extracts and movements between places shown as edges, can be analyzed in different network arrangements, which reveal spatial and temporal topologies of movement data. We implemented a web-based prototype and report on challenges and opportunities about a novel network layout of places gathered during a qualitative evaluation.

Publication Website

WanderVis - Interaktive Visualisierung von Bevölkerungsbewegungen

Planerin Fachzeitschrift für Stadt-, Regional- und Landesplanung (2), 27-30, 04/2018
Dirk Andres Martin Memmel Till Nagel

Für die Stadt Kaiserslautern werden soziodemografische Daten aufbereitet und ausgewertet, sodass Einwohnerzahlen oder Bewegungssalden als interaktive Visualisierungen nutzerzentriert zugänglich gemacht werden. Datenvisualisierung erleichtert die Interpretation von Informationen und unterstützt so eine stärkere Nutzung in der Praxis.

Project Website Publication

Shanghai Metro Flow – Multiple Perspectives into a Subway System

Leonardo, MIT Press Journals, Volume: 50, Issue: 5, p.511-512, 10/2017
Till Nagel Benedikt Groß

One of the main characteristics of cities is the large amount of people moving around. These flows are reflected in all the subways dashing through the city. With our visualizations we want to give an impression of this pulse of the city. In this art show submission, we present Shanghai Metro Flow, which consists of an animation, and an accompanying infographic poster. The animation is composed of three scenes, each giving another perspective into the metro network. The static poster shows details on the subway lines. Each visualization combines established techniques with an highly aesthetic form in order to attract people to observe and dwell on different aspects of urban mobility.

pdf Video

Staged Analysis: From Evocative to Comparative Visualizations of Urban Mobility

Proceedings of the IEEE VIS Arts Program (VISAP), Baltimore, USA, 10/2016
Till Nagel Christopher Pietsch Marian Dörk

In this paper we examine the concept of staged analysis through a case study on visualizing urban mobility exhibited in a public gallery space. Recently, many cities introduced bike-sharing in order to promote cycling among locals and visitors. We explore how citizens can be guided from evocative impressions of bicycling flows to comparative analysis of three bike-sharing systems. The main aim for visualizations in exhibition contexts is to encourage a shift from temporary interest to deeper insight into a complex phenomenon. To pursue this ambition we introduce cf. city flows, a comparative visualization environment of urban bike mobility designed to help citizens casually analyze three bike-sharing systems in the context of a public exhibition space. Multiple large screens show the space of flows in bike-sharing for three selected world cities: Berlin, London, and New York. Bike journeys are represented in three geospatial visualizations designed to be progressively more analytical, from animated trails to small-multiple glyphs. In this paper, we describe our design concept and process, the exhibition setup, and discuss some of the insights visitors gained while interacting with the visualizations.

Project Publication

Open Geo Tools — A State of the Art Report. The democratization of geo-tools and data continues

Proceedings of the 64th German Cartography conference, 10/2016
Sebastian Meier Till Nagel Frank Heidmann

In our talk we want to give an overview of the current state of open mapping tools. To systematize the expanding field of modern geo tools, we are proposing a new taxonomy, which helps us cluster and categorize the tools, as well as highlighting various dimensions of their functionality. In our talk, we will show examples of how these tools can be used in research as well as professional use cases. By showing how far this field has come, we are trying to highlight how a field that was formerly expert only, has become an open space for collaborations, bringing together geo experts, researchers from other fields, designers as well as citizens themselves. We will also discuss some of the critical issues with this process, such as the overuse of a single map projection, suboptimal generalization, inappropriate color choices, and generally trying to re-invent some well-established techniques due to knowledge gaps. By providing this state of the art report, we are attempting to point out how important it is for us as a professional and academic community to participate in this emerging field, and help foster an exchange of knowledge with the community who create those tools and datasets.


From Origins to Destinations - The Past, Present and Future of Visualizing Flow Maps

Built Environment volume 42(3), special issue on Big Data and the City, pp. 338-355, 09/2016
Matthew Claudel Carlo Ratti Till Nagel

Flow maps are an established cartographic method to depict movements over time and space. In recent years, the exponential increase of geospatial information – what we call urban ‘big data’ – has introduced new uses and highlighted the need to expand cartography. In this paper, we define existing visualization strategies and tools, and examine their characteristics. From this, we identify challenges and opportunities for data-driven flow maps and suggest future developments. Specifically, we apply a new taxonomy to compare several geospatial data visualizations from the MIT Senseable City Lab and extract principles that can define the capabilities of a new interactive flow mapping tool. We have begun to work on such a tool – called the Datacollider – that is public, powerful, intuitive, and scalable. In the latter portion of this paper, we describe the Datacollider, detail its limitations, and outline directions for future development. We conclude by extrapolating broader trends for the field of geospatial data visualization. We articulate a shift from visualization as a set of graphic tools for representing found insights, to visualization as a way of engaging with data and deriving knowledge.

pdf publication

Are there networks in maps? An experimental visualization of personal movement data

Proceedings of the IEEE VIS 2015 Personal Visualization Workshop, 10/2015
Heike Otten Lennart Hildebrandt Till Nagel Marian Dörk Boris Müller

Shifted Maps proposes a novel visualization method to generate personal geovisualizations of individual movement data. The resulting visual appearance can be characterized as a map network consisting of visited places and their connections. The visited places are shown as circular map extracts scaled according to the time spent there and the movements between the places are represented as edges between the places. A key feature of the Shifted Maps visualization is the possibility to explore the data in three different arrangements based on geo-spatial position, travel time, and frequency of movements. By combining map and network visualizations of movement data, it becomes possible to analyze and compare spatial and temporal topologies.

pdf Project Video

Making three Cases for Casual Geovisualizations on Interactive Surfaces

In Proceedings of the ACM ITS 2015 Workshop on Data Exploration for Interactive Surfaces, pp. 24 – 27, 10/2015
Till Nagel

In this paper, we present three case studies on visualizing spatiotemporal data on interactive tabletops and surfaces for casual use. While there is a growing interest among citizens to make sense of their social community and urban environment, most existing geovisualization tools have been designed for experts such as planners and analysts. We introduce situation-specific visualization systems that were particularly designed for public exhibitions to balance powerful data exploration methods with inviting accessibility for laypeople. Finally, we discuss some of the lessons learned regarding people’s interest, interaction conventions, and information aesthetics.


Isoscope – Visualizing temporal mobility variance with isochrone maps

Poster Abstracts of IEEE VIS 2014, 09/2014
Flavio Gortana Sebastian Kaim Martin von Lupin Till Nagel

Isochrone maps are an established method to depict areas of equal travel time, and have been used in transportation planning since the early 20th century. In recent years, interactive isochrone maps allowed users to select areas of interest, or explore temporal mobility patterns for different modes of transport. However, conventional isochrone maps depict one traffic situation at a time. Our visualization approach unifies isochrone maps with time-varying travel data, and instead of showing multiple isolines for different travel times, we show multiple isolines for different times of day in order to reveal time-dependent spatial travel variance. In this paper, we present Isoscope, a web application that provides an interactive map for casual exploration of urban mobility patterns. Through its aesthetic visual form and its simple interface we strive to support people investigating travel time in their own city. We will describe our design goals, elaborate on the design and implementation of our prototype, and discuss limitations and future extensions of the system.

pdf Project Poster

Touching Transport – A Case Study on Visualizing Metropolitan Public Transit on Interactive Tabletops

In Proceedings of the International Working Conference on Advanced Visual Interfaces, pages 281-288, ACM, 07/2014
Till Nagel Martina Maitan Erik Duval Andrew Vande Moere Joris Klerkx Kristian Kloeckl Carlo Ratti

Due to recent technical developments, urban systems generate large and complex data sets. While visualizations have been used to make these accessible, often they are tailored to one specific group of users, typically the public or expert users. We present Touching Transport, an application that allows a diverse group of users to visually explore public transit data on a multi-touch tabletop. It provides multiple perspectives of the data and consists of three visualization modes conveying tempo-spatial patterns as map, time-series, and arc view. We exhibited our system publicly, and evaluated it in a lab study with three distinct user groups: citizens with knowledge of the local environment, experts in the domain of public transport, and non-experts with neither local nor domain knowledge. Our observations and evaluation results show we achieved our goals of both attracting visitors to explore the data while enabling gathering insights for both citizens and experts. We discuss the design considerations in developing our system, and describe our lessons learned in designing engaging tabletop visualizations.

pdf Slides Video

Traffic Origins - A Simple Visualization Technique to Support Traffic Incident Analysis

IEEE Pacific Visualization Symposium, 04/2014
Afian Anwar Till Nagel Carlo Ratti

Traffic incidents such as road accidents and vehicle breakdowns are a major source of travel uncertainty and delay, but the mechanism by which they cause heavy traffic is not fully understood. Traffic management controllers are tasked with routing repair and clean up crews to clear the incident and often have to do so under time pressure and with imperfect information. To aid their decision making and help them understand how past incidents affected traffic, we propose Traffic Origins, a simple method to visualize the impact road incidents have on congestion. Just before a traffic incident occurs, we mark the incident location with an expanding circle to uncover the underlying traffic flow map and when it ends, the circle recedes. This not only directs attention to upcoming events, but also allows us to observe the impact traffic incidents have on vehicle flow in the immediate vicinity and the cascading effect multiple incidents can have on a road network. We illustrate this technique using road incident and traffic flow data from Singapore.


Unfolding – A Library for Interactive Maps

In: SouthCHI, Human Factors in Computing and Informatics, Lecture Notes in Computer Science LNCS, volume 7946, pp. 497-513, Springer, 01/2013
Till Nagel Erik Duval Andrew Vande Moere Joris Klerkx

Visualizing data with geo-spatial properties has become more important and prevalent due to the wide spread dissemination of devices, sensors, databases, and services with references to the physical world. Yet, with existing tools it is often difficult to create interactive geovisualizations tailored for a particular domain or a specific dataset. We present Unfolding, a library for interactive maps and data visualization. Unfolding provides an API for designers to quickly create and customize geovisualizations. In this paper, we describe the design criteria, the development process, and the functionalities of Unfolding. We demonstrate its versatility in use through a collection of examples. Results from a user survey suggests programmers find the library easy to learn and to use.

pdf Code Project Slides

Interactive Exploration of a Geospatial Network Visualization

In Proceedings of the 2012 ACM Annual Conference Extended Abstracts on Human Factors in Computing Systems, pp. 557-572, ACM, 10/2012
Till Nagel Erik Duval Andrew Vande Moere

This paper presents a tabletop visualization of relations between geo-positioned locations. We developed an interactive visualization, which enables users to visually explore a geospatial network of actors. The multitouch tabletop, and the large size of the interactive surface invite users to explore the visualization in semi-public spaces. For a case study on scientific collaborations between institutions, we applied and improved several existing techniques for a walk-up-and-use system aimed at scientists for a social setting at a conference. We describe our iterative design approach, our two implemented prototypes, and the lessons learnt from their creation. We conducted user evaluation studies at the two on-location demonstrations, which provide evidence of the prototype usability and usefulness, and its support for understanding the distribution and connectivity in a geospatial network.

pdf Slides

Sankey Arcs – Visualizing edge weights in path graphs

Eurovis 2012, Vienna, Austria, 5-8 June 2012, Eurovis 2012, pp. 55-59, Eurographics Association, 01/2012
Till Nagel Erik Duval Andrew Vande Moere Kristian Kloeckl Carlo Ratti

Arc diagrams allow exploring relations and their strength between sequential nodes. Previous solutions suffer from displaying all arcs at the center of a node, which can lead to visual obstruction. We present a new technique, which extends the arc diagram technique by laying out the weighted edges of a node adjacent to each other. The aim of our Sankey Arc technique is to improve clarity, to enable users perceiving and comparing weighted edges in path graphs. The technique is illustrated using a dataset on travel paths in a public transit network.

pdf Slides