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Hofer Barbara

A Language to Describe Geographic Physical Processes

Geography investigates changes in physical structures and in distributions of objects
in space; these structures and distributions are shaped by processes. Models of processes
are built in order to understand and analyze the observed changes. Geographic
information systems (GIS), helping with space related analyses, play a supportive role
for spatial process modeling due to their static nature. The integration of the concepts
related to processes in GIS is one of the unsolved issues of geographic information
science.
The goal of this research is to better understand requirements of process modeling
in order to extend GIS with functionality for process modeling in the long term.
The integration of sophisticated process modeling capabilities in GIS that address
the specialized methods of different application areas and disciplines is not realistic.
An abstraction from details of quantitative process modeling is required to identify
generic process modeling functionality.
This research carries out a systematic analysis of mathematical models of geographic
processes with a focus on geographic physical processes in order to develop
a generic method to describe these processes: a process description language. This
language consists of:
  • a vocabulary consisting of mathematical operators to describe the model;
  • composition rules for combining the terms of the vocabulary to models;
  • a visual user interface to guide through the modeling procedure.
The approach to the specification of a vocabulary of the process description language
focuses on existing knowledge on modeling physical processes with deterministic models.
Geographic physical processes are a subgroup of physical processes, which suggests
the applicability of physical principles to the modeling of geographic physical
processes. The physical principles referred to are conservation principles that specify
the behavior of continuous physical processes. An analysis of the mass conservation
equation leads to the vocabulary of the process description language. The foundation
of the vocabulary in mathematical equations provides the rules for composing
the terms of the vocabulary. The user interface is derived from the general procedure
of establishing deterministic process models.
The result of this research is a process description language that provides a possibility
to describe process behaviors on a general level and to compose descriptions of
process components to models. A user interface guides the user from a conceptualization
of a process to equations modeling the process.
The application of the process description language is tested for two geographic
physical processes: the spread of a pollutant in a lake and the dispersion of exhaust
fumes of a factory. The output of the application of the process description language
is the specification of the behavior of a process together with the indication of required
parameters, initial and boundary conditions. The resulting models are considered as
sketch models that provide the required information to simulate the processes. This
research provides the basis for the implementation of a process description tool that
supports the linkage of process modeling and GIS.

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