Simulating geographic phenomena in a realistic and plausible way requires real-world entities to be abstracted based on the dynamic physical characteristics they exhibit, and treated as individuals in a simulation domain. These processes cannot be adequately supported by the traditional spatial model based on cellular-space such as Cellular Automata (CA). Although this approach has received a great attention as a most favoured technique for simulating the geographic phenomena from different aspects, the need for a generic spatial model to overcome the limitations encountered in such an approach has been raised. This applies particularly to the way real-world entities are represented in a simulation domain regarding their physical characteristics and temporal aspects.
In this thesis, a new computational approach for a spatial model suitable for simulating geographic phenomena is presented: the vector agents model. The vector agent is goal-oriented, adaptable, physically defined by an Euclidean geometry and able to change its own geometric characteristics while interacting with other agents in its neighbourhood using a set of rules. The agent is modelled with sensor, state, and strategies. The successful implementation of the model�s architecture allows the representation of the physical characteristics of real-world entities and to observe their complex and dynamic behaviour in a simulation domain. Vector agents have developed out of a need to create a systematic basis for the geometric components of Geographic Automata Systems (GAS), as outlined by Torrens and Benenson (2005).
A generic vector agents model was built, then tested and validated from different aspects, from which results demonstrated the model�s efficiency. It is confirmed that vector agents are flexible in producing different complex shapes and patterns for recreating real geographic phenomena through the generic use of three algorithms of geometric manipulation: midpoint displacement by using the relaxed Brownian Motion (fractal-like) algorithm, edge displacement and vertex displacement. The effectiveness of this was initially ascertained visually. A simple heuristic to govern shape growth rate and complexity was derived based on the interplay of the three algorithms. There was a further abstract model comparison against the cellular-agents environment, with the result that vector agents have the ability to emerge patterns similar to what can be produced by cellular-agents with the advantage of representing entities as individuals with their own attributes with realistic geometric boundaries. On the other hand, the city as a complex geographic phenomenon was used as a specific domain for validating the model with a real-world system. The results of the urban land use simulations (driven by simple rules based on three classical urban theories) confirmed that: (a) the model is flexible enough to incorporate various external rules based on real-world systems and (b) the model has a sufficient capability in emerging a variety of patterns under several environments close to actual patterns. The agent environment also proved to be an effective way of easily combining the rules associated with each urban theory (different agents behaved according to different theories). Finally, limitations raised through the development of this work are addressed leading to outline possible extensions of both model computation and the domain of applications.
| Identifer | oai:union.ndltd.org:ADTP/217833 |
| Date | January 2008 |
| Creators | Hammam, Yasser, n/a |
| Publisher | University of Otago. Department of Information Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Yasser Hammam |
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