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Modeling in GIS. Andrew T. Rowan, Ph.D. Director, The GIS Center at Stony Brook. What is a Mathematical Model?. A mathematical representation of the processes of interest that act in some real-world system.
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Modeling in GIS Andrew T. Rowan, Ph.D. Director, The GIS Center at Stony Brook
What is a Mathematical Model? A mathematical representation of the processes of interest that act in some real-world system. It is by definition a simplification of the natural system’s functioning; the nature of the simplification depends on the application for which the model is designed.
Modeling Within GIS • Simple to intermediate models often implemented completely within the GIS software • Complex models • Often not practical to rewrite within GIS • GIS helps prepare data files • Visualization of results
Simple Nonpoint-Source Model Example: Unit Areal Loading • Total area of each major landcover in the watershed • Multiply areas by average loading factors, kg/year • Result is annual nitrogen & phosphorous load to outlet
Soil Erosion • Universal Soil Loss Equation • Predicts soil loss from wind, water • Uses soil erodibility factor, slope • GIS implementations by various researchers
Complex Water-Quality Models • Fully-developed computer programs • Implementation of sophisticated equations for many different processes within the system • Data-intensive • Parameters of model must be calibrated to accurately represent a given system • GIS makes easier to carry out, not easier to carry out PROPERLY