GEOG 485:
GIS Programming and Automation

1.2.4 Modeling with tools

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When you work with geoprocessing, you’ll frequently want to use the output of one tool as the input into another tool. For example, suppose you want to find all fire hydrants within 200 meters of a building. You would first buffer the building, then use the output buffer as a spatial constraint for selecting fire hydrants. The output from the Buffer tool would be used as an input to the Select by Location tool.

A set of tools chained together in this way is called a model. Models can be simple, consisting of just a few tools, or complex, consisting of many tools and parameters and occasionally some iterative logic. Whether big or small, the benefit of a model is that it solves a unique geographic problem that cannot be addressed by one of the “out-of-the-box” tools.

In ArcGIS, modeling can be done either through the ModelBuilder graphical user interface (GUI) or through code, using Python. To keep our terms clear, we’ll refer to anything built in ModelBuilder as a “model” and anything built through Python as a “script.” However, it’s important to remember that both things are doing modeling.