Introduction of Geoprocessing
Lecture 9
3/24/2008
Geoprocessing
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Geoprocessing is any GIS operation used to manipulate data.
A typical geoprocessing operation takes an input dataset,
performs an operation on that dataset, and returns the result of
the operation as an output dataset or derived data. Common
geoprocessing operations, like:
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geographic feature overlay
feature selection and analysis
topology processing
data conversion.
Geoprocessing allows you to define, manage, and analyze
geographic information used to make decisions. In other
words, any alteration or information extraction you want to
perform on your data involves geoprocessing.
Geoprocessing
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Geoprocessing is one of the most powerful components of a GIS. In
ArcGIS® Desktop, you are provided with a framework for addressing
geoprocessing tasks, which includes an extensive list of geoprocessing
tools organized within a set of toolboxes.
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You can employ the tools directly or chain them together to model a
particular workflow. You can put geoprocessing tools to work in custom
scripts and you can create your own tools and toolboxes.
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The geoprocessing framework also provides functionality for organizing
and managing your work environment, performing simple and complex
analyses, and making your custom tools usable by others.
Geoprocessing with ArcGIS
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The most important thing to understand about geoprocessing
in ArcGIS Desktop is that all geoprocessing operations
involve the use of tools.
Geoprocessing
GIS project steps
GIS project steps
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1. Determine the objectives of the project
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Identify the problem to solve
Break down the problem into measurable criteria
Determine data requirements
2. Build the database and prepare the data for
analysis
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Identify and obtain relevant data
Design and implement the database
Add spatial and attribute data to the database
Manage and modify the data
GIS project steps
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3. Perform the analysis
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4. Present the results
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Determine methodology and sequence of operations
Process the data
Evaluate and interpret the results
Refine the analysis as needed and generate alternatives
Create final products for intended audience
5. Document your work
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As you progress through the four major steps of a GIS project, careful
documentation serves as a record of your methodology, so that you
can easily duplicate your workflow and share your work with others.
Find the right tool for the job
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Familiar with the toolbox
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Favorite tab
Index tab
Search tab
Using the index tab to find a tool works well when you have a
pretty good idea about what the tool's name is. Otherwise,
you will want to use the Search tab.
If you need more detailed information about the tool, you
could click the Help button at the top of the help panel to
open a more comprehensive help document for the tool. You
can also access this information by right-clicking a tool in
ArcToolbox and choosing Help.
Explore system toolboxes in the Catalog Tree
Create your own tool
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In addition to the system tools, toolsets, and
toolboxes that come with the software, you can
create your own. For example, you might create a
new toolbox to store custom script tools for a
particular project.
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Save the ArcToolbox settings to a file before any
change. Then, you can load the settings if you make
any mis-operations.
Both system tools and custom tools can be managed
using ArcToolbox
Customized tools
Create your own tool
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Within an ArcGIS Desktop session, any changes you make to
ArcToolbox in ArcCatalog will not automatically display in
ArcMap.
To match the ArcToolbox settings in ArcMap or other ArcGIS
Desktop applications with those in ArcCatalog, you have
three choices:
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Close ArcCatalog before opening another ArcGIS Desktop
application.
Save the ArcToolbox settings as the default in any ArcGIS Desktop
application, then open another ArcGIS Desktop application.
Save the ArcToolbox settings to a file in any ArcGIS application. In
the ArcGIS Desktop application, load the ArcToolbox settings from
the file.
Run a tool from the command line
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The command line gives you an alternative to
using a dialog box to run a tool. You type the
name of the tool and its parameter values as
text in the command line, and press Enter to
run the tool.
Click the Show/Hide Command Line Window
button to display the Command Line window
Set up the environment settings before run
command line
Command Line window
Create & run your own Model
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A model can link tools together to execute multiple processes
as one operation.
Models contain geoprocessing tools, but they are also
considered tools themselves.
Models allow you to document your methodology and share
your work with others because they provide a record of your
workflow
Create & and run your own scripts
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Scripts
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Script is a text file that contains instructions for
geoprocessing written as lines of code.
Any processing that you can do with a model can also be
done using a script. However, scripts offer additional
functionality that is not available using a model.
To run a geoprocessing script using ArcMap or
ArcCatalog, you must first attach the script to a tool.
Scripts and models contain geoprocessing tools, but they are also
considered tools themselves.
Scripts allow you to document your methodology and share your
work with others, because they provide a record of your workflow
Script