Exploring multivariate representations of indices along linear geographic features

A study of the walkability of a Swiss town required finding suitable representations of multivariate geographical data. The goal was to represent multiple indices of walkability concurrently and visualizing the data …

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Abstract

A study of the walkability of a Swiss town required finding suitable representations of multivariate geographical data. The goal was to represent multiple indices of walkability concurrently and visualizing the data along the street network it relates to. Different indices of pedestrian friendliness were assessed for short street sections and then mapped to an overlaid grid. Basic and composite glyphs were designed using square- or triangle-areas to display one to four index values concurrently within the grid structure. Color was used to indicate different indices. Implementing visualizations for different combinations of index sets, we find that single values can be emphasized or de-emphasized by selecting the color scheme accordingly and that different color selections either allow perceiving single values or overall trends over the evaluated area. Values for up to four indices can be displayed in combination within the resulting geovisualizations and the underlying gridded road network references the data to its real world locations.

Figures

a) Excerpt of the road network with composite glyphs showing two indices using somewhat associative colors of differing lightness, the index showing street lighting in yellow and the slope index in black; b) excerpt of the road network with composite glyphs showing three indices using colors with very similar lightness values, shop accessibility pink, public transport accessibility blue and greenery green.

Cropped illustration of the road network split-up in smaller sections (roads in black, dots indicating ends of sections) and overlaid grid. Grid cells in gray indicate cells where variable values from the road sections were assigned.

Excerpt of a representation of the variation of a single index along a road network through color hues. Darker blueish color hues denote larger index values and lighter yellowish color hues denote smaller index values. (Source: Hollenstein & Bleisch, 2016, p707)

Excerpt of the univariate representation of the index value ‘greenery’ through proportional symbols (areas of squares) along the road network. The variation of the values can be perceived concurrently with the abstracted street network layout.

a) Four grid cells, each subdivided into four spaces to indicate the available space for up to four value representations; b) example of four single values represented through square areas each of which is located at the center of a grid cell (basic glyphs); c) example of four composite glyphs each showing two index values through diagonally arranged square areas; d) example of four composite glyphs showing three index values through triangle areas; e) example of four composite glyphs showing four index values through square areas.

a) Excerpt of the road network with composite glyphs showing index values as triangle areas with some positive (green) and a neutral (grey) place indications in the background; b) excerpt of the road network with composite glyphs showing index values as square areas with some negative (red) place indications in the background.

BibTeX

@article{bleisch_exploringMultivariateIndicesAlongLinearFeatures_2018,
 abstract = {A study of the walkability of a Swiss town required finding suitable representations of multivariate geographical data. The goal was to represent multiple indices of walkability concurrently and visualizing the data along the street network it relates to. Different indices of pedestrian friendliness were assessed for short street sections and then mapped to an overlaid grid. Basic and composite glyphs were designed using square- or triangle-areas to display one to four index values concurrently within the grid structure. Color was used to indicate different indices. Implementing visualizations for different combinations of index sets, we find that single values can be emphasized or de-emphasized by selecting the color scheme accordingly and that different color selections either allow perceiving single values or overall trends over the evaluated area. Values for up to four indices can be displayed in combination within the resulting geovisualizations and the underlying gridded road network references the data to its real world locations.},
 author = {Bleisch, Susanne and Hollenstein, Daria},
 doi = {10.5194/ica-proc-1-11-2018},
 journal = {Proceedings of the ICA},
 title = {Exploring multivariate representations of indices along linear geographic features},
 url = {https://ica-proc.copernicus.org/articles/1/11/2018/},
 year = {2018}
}