Exploratory Access to Geographic Data

Many geographic information systems (GISs) attempt to imitate the manual process of laying transparent map layers over one another on a light table and analyzing the resulting configurations. While this map-overlay metaphor, familiar to many geo-scientists, has been used as a design principle for the underlying architecture of GISs, it has not yet been visually manifested at the user interface. To overcome this shortage, a new direct manipulation user interface for overlay-based GISs has been designed and prototyped. It is characterized by the separation of map layers into data cubes and map templates such that different thematic data can be combined and the same kind of data can be displayed in different formats. This paper introduces the conceptual objects that the user manipulates at the screen surface and discusses ways to visualize effectively the objects and operations upon them.