2019, Nagel, Fabian, Castiglia, Giuliano, Ademaj, Gemza, Buchmüller, Juri F., Schlegel, Udo, Keim, Daniel A.

The goal of the VAST challenge 2019 Mini Challenge 2 was to visualize radioactive contaminations measured by mobile and static sensors and their changes over time, allowing city officials to determine the severity of the leakage at the city's nuclear power plant. We propose cpmViz, a web-based tool that allows for interactive data exploration of the sensor readings in both of the spatial and temporal dimensions. The tool consists out of three views that are connected via linking and scrolling. We visualize static sensor uncertainty by introducing Voronoi cells to illustrate how much space is covered by an individual measurement unit. For mobile sensors, we showcase their activity periods and introduce the concept of sensor streaks as periods of uninterrupted recordings as a temporal uncertainty measure. As for spatial uncertainty, we color individual districts based on the amount of data that was recorded inside the user's selected time window. Using our system, we were able to easily spot major events like the city's initial earthquake in the sensor readings. Certain southern districts are clearly visible as areas of concern that we consider in need of more static sensors. Furthermore, we were also able to identify static as well as moving contaminations.

2018, Cakmak, Eren, Seebacher, Daniel, Buchmüller, Juri F., Keim, Daniel A.

The goal of the VAST Challenge 2018 Mini Challenge 2 (MC 2) was to unveil the possible causes and effects of environmental pollution in the Boonsong Lekagul Wildlife Preserve. We propose the ViCCEx (Visual Chemical Contamination Explorer) system that enables to interactively explore the sparse multivariate river network sensor reading dataset to identify characteristics, trends, and outliers of the different sensor reading locations over time. The ViCCEx system uses a t-SNE projection to display an overview visualization, a sampling strategy view to highlight the overall sampling strategies of different chemical measurements at each sensor location, and various extracted statistics to highlight the evolution of chemical measurements. The three views are connected via linking and brushing, which enables to explore and identify possible pollution causes and effects in the preserve.