Map Morphing is an interactive morph between two maps covering approximately the same region. Using both blending and distortion, the maps appear to merge into one another. This allows the user to directly visualize how the two maps diverge from one another in their presentation.
This is particularly useful when one or both maps provide views that aren't spatially accurate (such as the typical "schematic" subway map).
We currently generate short movie sequences (between 10-20 frames), which the user controls with a slider (blending and distortion are not independently controlled). In this way they can interactively build an understanding of how the two maps are related. The movie sequences are created using the free MorphX software.
An exploratory study compared the technique against other ways of relating maps. Three different pairs of maps were used (Europe-Middle East ancient/modern, London subway/street, and Toronto transit/tourist). User evaluations were positive, and participants were more likely to correctly complete certain navigation tasks using the morphing interface [2].
This larger study explored more specifically whether morphing helps to build a lasting understanding of map interrelationships. Results indicate that the technique's effectiveness for recall of relationships is affected by the setting in which it is used. Participants who used the technique in a casual, noisy atrium environment had better recall than those who used it in a controlled, quiet white room [1], while the same effect was not found for juxtaposing maps.