How useful are interactive small multiples for the visualization of overlapping areal information? An expert evaluation in spatial planning

Multidimensional spatial data is used in various application domains, such as spatial planning or risk management. The datasets are often layered within single maps, where overlapping information can create complex and …

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Abstract

Multidimensional spatial data is used in various application domains, such as spatial planning or risk management. The datasets are often layered within single maps, where overlapping information can create complex and potentially misleading displays. This study investigates the use of an interactive small multiples layout, where web maps with a common spatial area, each representing a different topic, are arranged side by side for simultaneous viewing. Spatial planning served as the use case, as it involves the concurrent analysis of multiple topics within a defined area. Domain experts participated in a qualitative usability study, carrying out typical planning tasks. Their feedback on the small multiples layout regarding task effectiveness, efficiency, and satisfaction (usability) was evaluated through qualitative content analysis. We learned that the layout enabled quick overviews and efficient cross-comparison between topics, particularly in the weighing of interests. All tasks were completed, and the feedback was predominantly positive. Limitations arose when the area under consideration extended beyond the boundaries of the small multiples map windows. We conclude that small multiples layouts are useful for the simultaneous visual analysis of multiple spatially coincident topics in web maps. The finding may generalize to other domains that use potentially overlapping multidimensional spatial data.

Figures

Layout 1 (left) is 12 maps laid out in a 3 × 4 grid. As only three maps are displayed per line, they are larger (15 × 10 cm per card) than in Layout 2 (11 × 7 cm per card), but the users must scroll down to view all cards. This prototype is accessible at https://go.fhnw.ch/V9Ce4F. Layout 2 (right) is also 12 cards arranged in a 4 × 3 grid. With standard desktop resolutions (16:9 aspect ratio, 24-inch screen with 1920 × 1080 resolution), all 12 cards are displayed simultaneously without having to scroll. To fit the screen, these maps are smaller than in Layout 1. This prototype is accessible at https://go.fhnw.ch/p5MaCz.

The map shows various topic areas in Switzerland (Glarus). The screenshots of the viewer, from which the topics are taken, only allow for a single map window, as shown in (a). As some of the topics overlap, they can no longer be properly visualized. To be legible, they would have to be individually selected and deselected in the selection menu. (b) shows what a possible small multiple representation might look like to overcome the problem of overlaps. The small multiples layout is currently not supported in the viewer where the screenshots are taken from (Fig. based on map.geo.admin.ch).

An example of a small multiples web map layout on the topic of risk overview for buildings from the Aargau building insurance company. The maps are used in the building permit process to identify risks posed by natural hazards (see https://die-agv.ch/static/gk/index.html) accessed: 08.07.2026.

The process sketch illustrates the process steps recommended in ISO standard 9241-210:2019 as implemented in this study with time dependencies and possible iterations in the development and determination of design solutions (extended, based on Jacobsen & Meyer, 2017).

Visual explanation of the zoom level problem. The 4 × 4 map block represents the fact that if the map window size remains small but the zoom level is increased, the map section must be moved around at least four times to see the entire perimeter. The bottom illustration shows how much the map window would hypothetically have to be enlarged if the zoom level is increased so that everything is visible again at once.

BibTeX

@article{reutimann_smallmultiples_2026,
 abstract = {Multidimensional spatial data is used in various application domains, such as spatial planning or risk management. The datasets are often layered within single maps, where overlapping information can create complex and potentially misleading displays. This study investigates the use of an interactive small multiples layout, where web maps with a common spatial area, each representing a different topic, are arranged side by side for simultaneous viewing. Spatial planning served as the use case, as it involves the concurrent analysis of multiple topics within a defined area. Domain experts participated in a qualitative usability study, carrying out typical planning tasks. Their feedback on the small multiples layout regarding task effectiveness, efficiency, and satisfaction (usability) was evaluated through qualitative content analysis. We learned that the layout enabled quick overviews and efficient cross-comparison between topics, particularly in the weighing of interests. All tasks were completed, and the feedback was predominantly positive. Limitations arose when the area under consideration extended beyond the boundaries of the small multiples map windows. We conclude that small multiples layouts are useful for the simultaneous visual analysis of multiple spatially coincident topics in web maps. The finding may generalize to other domains that use potentially overlapping multidimensional spatial data.},
 author = {Reutimann, Salome and Bronowicz, Carolin and Bleisch, Susanne},
 doi = {10.1080/23729333.2026.2696783},
 journal = {International Journal of Cartography},
 title = {How useful are interactive small multiples for the visualization of overlapping areal information? {An} expert evaluation in spatial planning},
 url = {https://www.tandfonline.com/doi/full/10.1080/23729333.2026.2696783},
 year = {2026}
}