Dealing with geographic continuous fields: the way to a visual GIS environment

Abstract

Recently, much attention has been devoted to the management of continuous fields, which describe geographic phenomena, such as temperature, electromagnetism and pressure. While objects are distinguished by their dimensions, and can be associated with points, lines, or areas, such phenomena can be measurable at any point of their domain by distinguishing what varies, and how smoothly. Thus, when dealing with continuous fields, a basic requirement is represented by users' capability to capture some features of a scenario, by selecting an area of interest and handling the involved phenomena.The aim of our research is to provide GIS users with a visual environment where they can manage both continuous fields and discrete objects, by posing spatial queries which capture the heterogeneous nature of phenomena. In particular, in this paper we propose a visual query language Phenomena, which provides users with a uniform style of interaction with the world, which is conceptually modeled as a composition of continuous fields and discrete objects. The intuitiveness of the underlying operators as well as of the query formulation process is ensured by the choice of suitable metaphors and by the adoption of the paradigm of direct manipulation.A prototype of a visual environment running Phenomena has been realized, which allows users to query experimental data by following a SQL-like SELECT-FROM-WHERE scheme.