Introduction of Geoprocessing
Lecture 9
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.
Explore system toolboxes
Search any tool you need
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.
Step2: Create a
new toolbox
Step1: Select
your geodatabase
as a Default
Geodatabase to
make sure all
outputs will be
stored there
Step4: you can
build your
model now
Step3:
Create a
new model
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
DEMOs from the Building Models for GIS Analysis using ArcGIS10
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
Details in next two lectures