Dynamic environmental modelling in GIS: 1. Modelling in three spatial dimensions

Environmental modelling languages are programming languages developed for building computer models simulating environmental processes. They come with database and visualization routines for the data used in the models. Environmental modelling languages provide the possibility to construct dynamic models, also called forward models, which are simulations run forward in time, where the state of the model at time t is defined as a function of its state in a time step preceding t. Nowadays, these modelling languages can deal with simulations in two spatial dimensions, but existing software does not support the construction of models in three dimensions. We describe concepts of an environmental modelling language supporting dynamic model construction in two and three spatial dimensions. The lateral dimension is represented by gridded maps, with a regular discretization, while the vertical dimension is represented by an irregular discretization in voxels. Universal spatial functions are described with these entities of the modelling language as input. Dynamic modelling through time is possible by combining these functions in structured script sections, providing a section, which is executed repetitively, representing the time steps. The concepts of the language are illustrated with two example models, built with a prototype of the language.