On December 15, 2015 at Montpellier (France), Mathieu Castets presented his PhD viva (oral defence) : Pavages réguliers et modélisation des dynamiques spatiales à base de graphes d’interaction : conception, implémentation, application
The modelling and simulation of spatial dynamics, particularly for studying landscape changes or environmental issues, raises the question of integrating different forms of spatial representations within the same model. Among the various existing spatial dynamics modelling tools (Cormas, Dypal, Netlogo, Seles, GAMA, etc.), Ocelet is a domain-specific language based on the original concept of interaction graph. Such a type of graph covers both the structure of a relation (which can be spatial, functional, hierarchical, social, etc.) between entities of a model and the semantics describing its evolution. The relationships between spatial entities are here translated into interaction graphs and these graphs are made to evolve during a simulation. While it is commonly accepted that space can be modelled with shapes with contours (vector format) or regular grid cells (raster), the concepts on which Ocelet is based can potentially handle both forms of representation. The vector format is already integrated in the first version of Ocelet. The integration of raster and the combination of the two remained to be studied and carried out.
The aim of the thesis is to first study the issues related to the integration of continuous fields and their representation by regular tiling, both in the Ocelet language and in the concepts on which it is based. The dynamic aspects of this integration had to be taken into account and transitions between different forms of geographic data and interaction graphs had to be studied in the light of the concepts formalized. The concepts were then implemented in the Ocelet modelling platform, with the adaptation of both its compiler and runtime. Finally, these new concepts and tools were tested in three very different cases: two models on Reunion Island, the first simulating runoff in Ravine Saint Gilles watershed in the West Coast of the island, the other simulating the spread of invasive plants in the high plains inside the Reunion National Park. The last case describes the spatialisation of a crop model and is applied here to simulate the cereal crop yields in West Africa, in the context of an early warning system for regional crop monitoring.