Forrest – CAUSES AND CONSEQUENCES OF SCALE CHANGE IN SCHEMATICS MAPS 2014

Description

This paper examines why and how scale changes occur in schematic maps—especially transport diagrams—and the effects on users. Scale distortion arises from network simplification, expanding dense information zones for legibility, and aesthetic manipulation; unlike systematic map projections, schematic distortions are often irregular and directional. Designers debate whether such diagrams qualify as maps, yet modern definitions accept them when spatial relationships are primary. Techniques to manage scale include insets, systematic focal distortions (magnifying-glass, polyfocal), octopus/spider maps, and temporal scaling by travel time. Users are generally unaware of scale variation because schematic symbols lack visual cues; familiar geographic context (rivers, streets) aids comprehension. Distortions matter when route choices exist: map distance strongly biases route selection—often twice as influential as travel time—potentially degrading journey efficiency. Remedies include showing walking links, link travel times, or interactive, route-specific replotting. Li’s four schematisation principles (topology, main structure, relativity in position and length) guide design, but the author argues for adding user-focused principles emphasizing travel time and end-to-end journey planning.