The Appearance: a design pattern for continuous field interfaces

Many of the data manipulated in a geographic information system are not discrete; instead, they must be treated as continuous fields. The ability to characterize a continuous field as a data type including related operations as well as estimation methods and the representation of the sampling points, facilitates the design and the use of this kind of data. However, the possibility to design and manipulate continuous fields is not enough to obtain a powerful tool, aspects related to the visualization of such data have to be also defined in order to realize spatial analysis. In this paper we present a flexible architecture to visualize data from continuous fields. Such architecture has been developed under the object-oriented paradigm, and the goal is to obtain a mechanism to allow the specification and evolution of the visual aspects independently of the implementation