Sergio Chiesa

Linguistic modelling of imperfect spatial information as a basis for simplifying spatial analysis

Spatial analysis is at the basis of several decision processes in fields such as urban planning and environmental management. In order to carry it out effectively more flexible Geographic Information Systems are needed to be able to represent and manage the imperfection that invariably affects geographic information. Starting from the consideration that experts usually deal with imperfect spatial information through linguistic terms (e.g., they identify the approximate position of a phenomenon on a map and classify spatial properties through linguistic labels), this contribution proposes the use of linguistic granule of information to represent and manage imperfect spatial information. A fuzzy object-based data model is proposed as a tool for supporting spatial analysis based on the management of linguistic granule. In particular, the problem of defining methods to manage imperfect information depending on the type of imperfection is discussed. Finally, an example of spatial analysis applied to support a decision problem in environmental impact assessment is described.

Subsurface thermal conductivity assessment in Calabria (southern Italy): a regional case study

Determining the suitability of a local area at a regional or local scale for the geothermal application of low enthalpy systems requires the knowledge of rock thermal conductivity values to evaluate the possibility of low-enthalpy heat exchange. A digital cartographic tool is also needed to synthesize the thermal properties of the underground. This tool should be easily accessible and upgradeable and thus suitable for territorial planning and environmental control. In order to address these key issues, a methodological approach was developed within the framework of the national VIGOR Project, dedicated to evaluating the geothermal potential in southern Italy. In this paper the region of Calabria was selected as a case study. Around 70 samples that were representative of the main geological formations were collected from all over the area. Thermal property tests were carried out both in dry and wet conditions, using a thermal device in accordance with the modified transient plane source method. The thermal conductivity values were then compared with data from the international literature. In order to consider the influence of the entire stratigraphic sequence on the thermal conductivity parameters, a geostatistical analysis of the available lithostratigraphic data was performed using the MATLAB toolbox Modalstrata, specially developed for this purpose. A comprehensive geothermal subsurface characterization of Calabria was thus obtained.

A fuzzy object-based data model for imperfect spatial information integrating exact objects and fields

In this contribution a fuzzy object-based data model for imperfect spatial information is proposed within the formal framework of fuzzy set theory and possibility theory. The proposal integrates the two opposite views of geographic entities seen as either exact objects or continuous fields in current Geographic Information Systems. By assuming a Fuzzy Object-Oriented Data modelling approach new data types for representing geographic entities characterized by either unsharp boundaries or indeterminate boundaries and relationships are defined.Linguistic qualifiers are adopted both to express the extent by which an element of the spatial domain satisfies a gradual property, and to identify regions with indeterminate boundaries.

A dual representation of uncertain dynamic spatial information

A dual representation of spatio-temporal phenomena whose observation is affected by uncertainty is proposed in the context of fuzzy set and possibility theory. The concept of fuzzy time validity of a snapshot of a dynamic phenomenon is introduced as well as the concept of possible spatial reference of the phenomenon at a given time instant. Then a mechanism to generate virtual snapshots of the phenomenon, showing its possible spatial reference at consecutive time instants, is described.

Representing and Querying Imperfect Spatio-Temporal Information in an Object-based Framework

Storing and managing large collections of spatio-temporal information is necessary in several applications to infer hidden knowledge from the study of the evolution of natural phenomena. For example, for the study of the variation of temperatures in a region, of the evolution of the soil coverage over a period of time, of the recurrence of natural hazards in critical areas, of the spreading of pollution or epidemics.

Modelling Imperfect Spatial Information in a Fuzzy Object Oriented Database

The adoption of an object oriented database model has been proposed as appropriate for GIS applications by several researchers [1,5,12]: it allows to develop a set of data types that maintain a one-to-one correspondence with geographic entities thus directly reflecting the human perception of the reality.