Spatial modeling by computer

Computer-based spatial models, representing the past and present disposition and configuration of sets of rock bodies, are a potentially important segment of a geological knowledge base. A spatial model is an interpretation that should be consistent with available data and with expectations based on knowledge of the processes which formed and deformed the rock bodies. The expectations refer not to the structure of the processes, but to their effects, which can be expressed as regional patterns, descriptive statistics, spatial relationships, material budgets, and balances. By using measures of these effects to control and modify interpolation, they can be taken into account in the modeling of surfaces and lines for display, measurement, analysis, and prediction. Processes which create features too small to be located from the data, contribute to an uncertainty envelope which can be defined around the interpolated surfaces. The conventional method of describing a conceptual spatial model is with maps and cross sections. These static two-dimensional images have limitations, not shared by digital models, in representing a fuzzy pattern in three dimensions of complex, interrelated surfaces. Maps are nevertheless unsurpassed as an aid to retrieval and visualization of spatial information. The advantages of both map and model can be obtained by the user generating displays from a digital model through interactive computer graphics.