Formal map specifications for a National Web Atlas

Abstract

For the generation of maps, a cartographer needs to know the data in advance in order to select the best map type to represent the data. The aim of this research was to formally specify of the process of selecting a map type, based on data characteristics to allow the automatization of the process. We studied as other authors described the process of representing data, to determine the necessary steps to generate a map. Then an informal description of these step was performed. The selection of the formal specification language was made through a study of the different types and characteristics of them. And finally, the process of selecting a map type based on data characteristics was formally specified for the study case of the experimental National Dutch Web Atlas. The properties from maps that should be specified are the visual variable and the geometry. The characteristics of the datasets that needs to be specified are the measurement scale, the attributes, and the geometry of the geographical component. Among the user’s requirements properties are the necessary for the selective perceptual property, the number of classes and the user’s preference for visual variable and geometry that makes the mark visible. The effectiveness and expressiveness of each visual variable and geometry also needs to be specified as a system knowledge. These properties are in Component, Algebra, Scale, Summary, Aesthetic and Geometry steps. The language selected for specifying the process is the Z specification language. And the process of selecting a map type based on the data characteristics was specified to the experimental National Dutch Web Atlas. The process was informally described for the generation of maps with one variable and for discrete data. The formal specification was executed using the Z language. Z is not ease to use, but will allow further specification of the process of generating a map. The process of selecting a map type based on data characteristics, taking into account certain user’s requirements was specified for the experimental National Dutch Web Atlas. However, further automation of the process still needs to be done.