Quantitative Line Glyphs to Visualize Multivariate Geometric Properties in Multi-scale Spatial data

Large differences in scale between the smallest items of interest and the full extent of data at focus pose challenges in the visualization of spatial data.Multivariate attributes further complicate the display of such information with the added challenge of representing multiple attributes simultaneously in an easily interpretable way.We introduce quantitative line glyphs to visualize multivariate attributes in visualizations of multi-scale geospatial data (Fig. 1).Their design is motivated by its application to the visualization of pavement roughness characteristics in the context of barrier-free routing and accessible urban planning.In barrier-free routing, structures of interest vary in size or amplitude from meters down to millimetres, while the length of the route may be 100 m or more.The need to visualize spatial structural information that spans several levels of scale is shared with other fields, e.g.biology (Cakmak et al. 2021).In the context of geospatial data, principles of cartographic generalization and abstraction are commonly applied to deal with a restricted display space and multi-scale information (Viola and Isenberg 2017;Cakmak et al. 2021).For our line glyph design, we draw upon such concepts to create dense, data-related glyphs which generalize to different view scales and work for 1D-(route representation) as well as 2D-visualizations (map representation).We combine the mapping of numeric attributes mostly to the visual variable length with the use of visual metaphors for surface profiles (Fig. 2).We map more than one attribute to each glyph element to create a condensed and generalized image of the underlying data.Visual metaphors and generalization are combined in other (linear) glyph designs to varying degrees (