Vizvariabler

Vizvariabler, or visual variables, are perceptual properties of map symbols and graphic marks that can be varied to encode data values in maps, diagrams, and other geospatial visuals. The concept originated with the cartographer Jacques Bertin and has become foundational in cartography, GIS, and information visualization. Visual variables help designers translate abstract data into perceptually separable features while aiming for accurate reading and comparison.

Common vizvariabler include position, size, value (lightness), hue (color), saturation (color intensity), texture, shape, orientation, and motion. Position refers to where a symbol is placed (on a map, this is geographic location; in charts it can be along an axis). Size encodes magnitude; value uses light-to-dark shading; hue and saturation manage color differences; texture differentiates areas through patterns; shape distinguishes categories; orientation rotates symbols to convey direction or emphasis; motion, in interactive or animated visuals, communicates change over time.

Data types guide how variables are used. Nominal data are often encoded with discrete hues, shapes, or textures. Ordinal data suit monotonic cues such as increasing size or lightness. Quantitative data benefit from strong, monotonic indicators like size, value, or spatial positioning where appropriate, though position on a map is ultimately constrained by geography rather than data value.

Design considerations include perceptual discriminability, accessibility (e.g., color vision deficiencies), and legibility in print and on screen. It is common to limit the number of variables used simultaneously and to ensure consistent legends and mappings across visuals. Typical applications include proportional symbol maps (size), choropleth maps (value via color), and dot-density maps (dot counts).