Geoprocessing in ArcGIS

Summary Geoprocessing is for everyone who uses ArcGIS. Whether you're a new user or an established user, geoprocessing is an essential part of your day-to-day work with ArcGIS. Geoprocessing allows you to automate complex workflows of a geographic information system (GIS) solution.

Geoprocessing is a fundamental part of ArcGIS. Geoprocessing provides the data analysis, data management, and data conversion tools necessary for GIS software users. Geoprocessing consists of tools that operate on ArcGIS data (tables, feature classes, rasters, triangulated irregular network [TINs], and so on) and perform tasks that are necessary for manipulating and analyzing geographic information across a wide range of disciplines. ArcGIS includes more than 600 geoprocessing tools. The essential artifacts of geoprocessing include ArcToolbox, tools, tool dialogs, tool parameters, models, and scripts.

This topic presents an overview of geoprocessing in ArcGIS and its artifacts.

ArcToolbox
Tool dialogs
Tool parameters
Models
Scripts

About geoprocessing in ArcGIS

The fundamental purpose of geoprocessing is to allow you to automate simple and complex GIS tasks. GIS solutions commonly involve a complex workflow of geographic analysis and data transformations. It is often necessary to automate, document, and share these GIS workflows.

Geoprocessing in ArcGIS supports the automation of workflows by providing a set of tools and a mechanism to combine a series of tools in a sequence of operations. GIS tasks that may need to be automated run from the routine—for example, converting data from one format to another—to the complex, using a sequence of operations to model and analyze spatial relationships. Examples of complex tasks include the following:

Calculating optimum paths through a transportation network
Predicting the path of wildfire
Analyzing and finding patterns in crime locations
Predicting areas that are prone to landslides
Predicting flooding effects of a storm event

Geoprocessing artifacts

What follows is a description of geoprocessing artifacts—the collection of user interface (UI) components that allow you to access and execute tools in ArcGIS.

ArcToolbox

ArcToolbox, a component of ArcCatalog and ArcMap, hosts the tools that are available to a GIS user. A typical geoprocessing tool performs an operation on an ArcGIS dataset (such as a feature class, raster, or table) and produces a new dataset as the result of the tool as shown in the following diagram:

Examples of a geoprocessing tool performing an operation on geographic data include the following:

Projecting a dataset from one map projection to another
Adding a field to a table
Creating a buffer zone around features

Tools in ArcToolbox are organized into toolboxes and toolsets, and ArcGIS ships with more than 600 tools that are organized into these toolsets and toolboxes, providing functionality across a wide range of disciplines. In ArcCatalog, ArcMap, ArcScene, and ArcGlobe, you can view the ArcToolbox window by clicking the Show/Hide ArcToolbox window button

on the Standard toolbar. The ArcToolbox window is shown in the following screen shot:

Tool dialogs

Each tool has a dialog, and the most common method for executing a tool is by using its dialog. The tool dialog allows you to interact with the tool. You provide the input and output values that are required to execute the geoprocessing task offered by the tool. A tool can have any number of parameters and, in the tool dialog, each parameter has an easy-to-use UI control for tasks such as browsing and selecting datasets, or choosing valid values from a list. Tool dialogs also verify the correctness of your inputs and can give you immediate feedback if there are problems. The Clip tool dialog is shown in the following screen shot:

In this example, the Clip tool clips features from the streets layer. The output feature class, streets_Clip3, contains only those features that fall within the StudyArea polygons. The output feature class is automatically created in the path specified by the output parameter.

Tool parameters

A tool parameter defines the characteristic of a tool. The values set for parameters influence a tool's behavior during run time. Tool dialogs provide the necessary UI for the parameters of the selected tool. A tool can have any number of parameters, and each parameter has its own UI control in the tool dialog. The most common parameter is the feature class, and its control, shown in the following screen shot, consists of a text box where you can type the pathname to a feature class and a Browse button (

) that enables you to select feature classes from disk. The text box typically has a drop-down list of available layers and table views from which you can choose.

Models

Geoprocessing models are sequences of tools chained together by linking the output of one tool into another. It allows you to preserve a set of tasks or workflows that you can execute multiple times. It is important to remember that models are tools. They behave the same way as all the other tools in the toolbox. Since models are tools, you can embed models within other models. The Clip and Buffer model is shown in the following screen shot:

Scripts

You can use a standard scripting language, such as Python, VBScript, or JScript, to create tools. As with models, tools that are based on scripts can be executed using their dialog box, and you can also use them in models and other scripts. An example of a script tool is shown in the following graphic: