Principles of Geovisualization in Map Animations

This short scientific essay was written for the course Principles of geovisualization in my third semester of CDE.

Characteristics of map animations

The process of translating a spatial dataset into a visualization results in a so-called map, and the possibilities and available methods for this are manifold. In cases of handling extremely large datasets, or the visualization of phenomena with a time component, static maps may become unreadable (Cartwright et al. 2007). Here, map animations allow to not only show temporal changes, but they can also depict changes in distributions and reveal patterns or trends which would not be obvious in a simple set of static maps (Peterson 1994).

Keyframe and frame-based animations

Another way of classifying map animations is the way how the transition of the change between the points of time is realized. The so-called frame-based animation is a simple sequence of several images which where created separately and get concatenated. This method allows for very simple animations in which as little as two frames of two different states are created and the switch from back and forth creates an animation that allows to see differences between the two images. By displaying many frames in a short time a smooth animation can be created, but this requires many individual images for each second of animation (Peterson 1994).

A second type of animation technique relies on keyframes where objects change dynamically between to specific states. All intermediate frames between those set keyframes get generated automatically and show a transition between the two states in a process called tweening. This is considered a more modern approach and allows a faster creation of map animations than the frame-based approach (Łucjan 2016).

Both of these animation aproaches are better suited for specific use cases. Discrete changes like the change of an ownership of a property can easily get visualized with frame-by-frame animation. Phenomena with continuous changes like movement of an object or change in temperature are easier to animate with cast-based animation techniques using colour cycling, metamorphosis or movement tweenings (Peterson 1994).

Animation variables

Mark Harrower proposed four general kinds of geographic change: change in location, change of areal extent or shape, changes in attribute and change of existence.
Along with further variables (order, duration, rate of change, display rate, frequency and synchronization) a large number of possibilities and adjustments for creating animations are available (Blok et al. 1999). However, the overuse of these variables is a high risk when creating map animations because the capacity of the viewer of processing information might be exceeded. The capacities of comparing sizes of symbols, colours of areas and reading text simultaneously is limited and makes evaluation and analysis of the animation content difficult (Łucjan 2016).

Challenges of map animations

The high level of required attention by the user and the possible overload of information was described by Morrison in 2000 and explained by four major challenges of map animations. Based on that, Mark Harrower in 2003 and Kamila Łucjan in 2016 proposed practical methods to tackle those challenges:

The high frequency of dramatic changes and the following chance that the viewer might miss important information was described as the challenge of disappearance. Adjusting the frame rate of the animation or artificially exaggeration the display time of very short events, which otherwise would only be visible for a short time, can help to overcome this issue.
Similarly, a high complexity of map animations can lead to confusion or mislead the user. The generalization of the vectors, simplifying the classification and filtering the dataset will prevent the user to be overwhelmed by the map animation. The attention of the user can be directed to important events using methods like flashing symbols or explanatory texts displayed at critical moments.
Lastly a major challenge of creating map animations to overcome the fear of the user to use the map. The confidence of the viewer has to be increased by possibly giving a guided instruction which explains the animation and possible control elements in detail. Otherwise the user might not be capable to understand the information visualized in the map animation (Harrower 2003; Łucjan 2016).

Interactive map animations

In addition, map animations are mostly much more efficient if the user has control over common actions like play, pause, slow, fast replay of the animation. Furthermore, interactions to switch on and off layers and to interact with visualized attributes will help to detect patterns, analyse statistics and to understand the overall spatio-temporal relationship of the animated phenomenon (Blok et al. 1999). With improved technology and the wider availability of mapping capabilities on the Internet, the possibilities and usefulness of map animations for the general public are greatly enhanced (Harrower 2003).

Conclusion

Many map animations are only created because this type of visualization looks impressive and attracts attention. A cartographic work can serve only to be an impressive or beautiful visualization without any further use. The general public usually reacts very positively to map animations and this can stimulate interest to geospatial topics (Harrower 2003). Nevertheless, the main purpose of geographic visualization is to transmit knowledge and to display understandable and analysable information. In the case of map animations, care must be taken respect and skillfully apply the fundamental principles of geovisualization of map animations described in this text. Complex animations that are overloaded have their right to exist and can have value as simple aesthetically impressive output. However, for map animations which are meant to explain information and to visualize spatio-temporal data as understandably as possible, compliance with the principles is important. Especially avoiding overloading the visualization must be avoided. If this is successful, map animations are a powerful visualization method and offer qualities that cannot be achieved by any other form of geovisualization.

References

Blok, Connie; Köbben, Barend; Cheng, Tao; Kuterema, Agnes A. (1999): Visualization of Relationships Between Spatial Patterns in Time by Cartographic Animation. In Cartography and Geographic Information Science 26 (2), pp. 139–151. DOI: 10.1559/152304099782330716.
Cartwright, William; Peterson, Michael P.; Gartner, Georg (op. 2007): Multimedia Cartography. With assistance of William Cartwright, Michael P. Peterson, Georg Gartner. 2nd ed. Berlin [etc.]: Springer.
Harrower, Mark (2003): Tips for Designing Effective Animated Maps. In CP (44), pp. 63–65. DOI: 10.14714/CP44.516.
Łucjan, Kamila (2016): Perception of the contents of animated maps. In Polish Cartographical Review 48 (4), pp. 149–160. DOI: 10.1515/pcr-2016-0015.
Peterson, Michael P. (1994): Spatial visualization through cartographic animation: theory and practice. In Proceedings of Geographic Information Systems / Land Information Systems GIS/LIS, pp. 250–258. Available online at http://maps.unomaha.edu/mp/Articles/GISLIS/VisAnim.html, checked on 11/21/2020.