Plan Information and its Retrieval in Map Interpretation: The View from Semiotics

Abstract

In mapping we convey information about space-occupying and localized objects, alternatively called places. Information is available through signs. It consists of concepts; concepts function as sign contents; these are conveyed by expressions; and expressions are linked to contents by virtue of rules. The information has plan components and plan-free components, which are intertwined. The discussion focuses on the plan components of the information, their conveyance, their retrieval in map interpretation, and the limits of such retrieval. Items of the plan information, shortly called content traits, are divided into internal and external traits. There are three classes of internal traits: cover form (a place is conceptualized as a unitary object, an occurrence range, or a field section), boundary form (from distinct to completely fuzzy), and characteristics of place definition. External traits are values of the variables of dimensionality, location, size, shape, and orientation. Content traits may or may not be formally expressed. Further, they may or may not be implied by object concepts. Where they are formally expressed, they are usually replicated as expression traits through the transformation of point coordinates. The resulting signs are images, i.e. motivated signs.

One generally wants to get factually adequate information from a map. Since map images are not completely faithful (e.g. for reasons of geometry), interpretation includes an assessment of the fidelity of a map. Motivation permits to infer content traits by virtue of similitude rules. Since these rules presuppose a faithful graphic rendering, they must be “relativized” by the knowledge of infidelities. It is shown what kinds of infidelities exist and how and to what extent the map user can know of them. In the interpretation process, infidelities may be mentally corrected, may only be recognized or assumed to be present, or may go unnoticed. The map interpreter assembles and integrates information from various sources. Map interpretation is a process of reasoning or inference which may be quite involved. It is based on rules which are learnt. Patterns of interpretative reasoning are exemplified; they all involve inferences which take account of infidelities. Apart from simple errors, three sources of such infidelities are identified: effects of coordinate transformation, method-produced misplacement, and shifts between differentially distinguished expression traits.