Circular icons to represent absolute values relating to areal features

The Atlas of the Ageing Society required methods to represent absolute values relating to areal features. As most of the displays in the atlas employ dots as symbols we aimed at finding methods to represent quantitative …

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Abstract

The Atlas of the Ageing Society required methods to represent absolute values relating to areal features. As most of the displays in the atlas employ dots as symbols we aimed at finding methods to represent quantitative values by an arrangement of dots. The arrangements need to work for a range of values and differently shaped areal features. Additionally, they should allow easy comparison of different values within a display. Some options for using dots as symbols on maps exist but none fulfills the specified requirements. We present two algorithms for dot arrangement. One is a squarish arrangement of dots that positions the dots in the center of the surrounding areal feature. The second is based on a regular grid. An inward buffer of the surrounding areal feature is applied to allow the correct number of dots to be contained within the area. Testing the two methods with different values and shapes yields promising results but also shows some limitations. Very large numbers or very small or irregular areal features remain a challenge. The presented methods will be applied and further tested in visualizations for the Atlas of the Ageing Society.

Figures

A basic shape filled with the buffer-based dot arrangement (left), a shape with a hole filled with the buffer-based dot arrangement (middle) and an irregular shape filled with the buffer-based dot arrangement (right)

An example of a dot distribution map. Each dot represents 100 indigenous persons and where approximately they live in Australia. (Australian Bureau of Statistics, 2008)

Absolute quantities of a phenomenon displayed through arranged Isotypes on a map. Each group of Isotypes relates to an area. However, the Isotypes are not generally enclosed by the respective shape but overlap neighboring shapes. (Gesellschaft und Wirtschaftsmuseum in Wien, 1931)

Three cantons of Switzerland as examples of basic shapes (left), shapes with holes (middle) and irregular shapes (right). (Data origin: swisstopo, 2017)

Squarish dot arrangement with 8 to 13 dots, displayed together with the underlying grid used for the arrangement.

Exemplary basic shape with defined grid (left), changing the buffer size until the correct number of dots can be arranged within (middle), the resulting dot arrangement (right).

A basic shape filled with a squarish dot arrangement (left), a shape with a hole filled with a squarish dot arrangement (middle), and an irregular shape filled with the squarish dot arrangement method (right)

Switzerland’s canton Freiburg with a hole in its boundaries representing an actual lake. This is an example where the number of dots in the arrangement might be overestimated (compare the dot arrangement left to the almost complete square of dots to the right). However, in this case it would be possible to eliminate the lake from the shape boundary and allow for a better dot arrangement.

BibTeX

@article{meyer_circularIcons4AbsoluteValuesinAreas_2017,
 abstract = {The Atlas of the Ageing Society required methods to represent absolute values relating to areal features. As most of the displays in the atlas employ dots as symbols we aimed at finding methods to represent quantitative values by an arrangement of dots. The arrangements need to work for a range of values and differently shaped areal features. Additionally, they should allow easy comparison of different values within a display. Some options for using dots as symbols on maps exist but none fulfills the specified requirements. We present two algorithms for dot arrangement. One is a squarish arrangement of dots that positions the dots in the center of the surrounding areal feature. The second is based on a regular grid. An inward buffer of the surrounding areal feature is applied to allow the correct number of dots to be contained within the area. Testing the two methods with different values and shapes yields promising results but also shows some limitations. Very large numbers or very small or irregular areal features remain a challenge. The presented methods will be applied and further tested in visualizations for the Atlas of the Ageing Society.},
 author = {Meyer, Philipp and Studer, Thomas and Bleisch, Susanne},
 journal = {Proceedings of the ICA},
 title = {Circular icons to represent absolute values relating to areal features},
 url = {https://api.semanticscholar.org/CorpusID:49543929},
 year = {2017}
}