Glyph-based Geovisualization of Temporal Data


Emmanuel Pietriga


The volume of geolocated data has grown dramatically in the last few years, as a consequence of the variety and number of producers of such data: geo-located posts on social networks, remote sensing devices, vehicles and transportation networks, etc. Those data often feature a temporal dimension, that is an essential piece of information for researchers and analysts who study, e.g., disease outbreaks, meteorological patterns and climate change, viral marketing and social behavior, online news propagation.

Visualizing geographical data that evolves over time helps detect interesting patterns and understand the data. But designing effective visualizations of temporally-evolving geolocated data remains challenging. The two most common approaches rely on animation on one side, and small multiples on the other side. Animations display time frames for different time steps in sequence, allowing the user to observe the data’s evolution as that evolution gets played back, typically at a user-controlled pace. Small multiples take a different approach: all time frames are displayed simultaneously, juxtaposed on screen. Animations will usually better convey the dynamics of the evolution, but require users to remember previous states when making comparisons as only one frame is visible at a time. Small multiples better support comparisons across time steps, but fail to convey the dynamics and do not scale well, as the size of each frame on screen decreases as the number of frames increases so that they can all be accommodated on the user’s display. The problem becomes even more complex when more than one geographical variable needs to be analyzed.

Glyph-based representations offer an interesting alternative to the two above strategies. The concept of glyph can be defined as a set of small, independent visual objects that depict a data record. They are commonly used to represent multivariate data. Glyphs have been used in prior work for the visualization of geo-temporal data, but mainly as a means to symbolize one or more variables at a specific geolocation that does not vary over time.

Description of Work

The goal of this project is to evaluate the potential of glyphs as a means to visually encode geographical data that evolves over time, not only in the attribute values, but also in the location of the entities these attributes are associated with.

More specifically, the research questions to be considered include:

The above research questions will be investigated by the postdoc, focusing on the following aspects:

The project is part of ILDA’s research on interactive, multi-scale geo-visualization, that represents a significant part of the team’s scientific output since 2015 (see references below for a representative set of publications). The post-doc is expected to contribute to this research axis by: designing novel visualization techniques, implementing them using the language and API of her choice, comparing them empirically to the state-of-the-art through user studies.

Skills and Profile