Creating Spatial Feature Classes Based on Proximity, Overlay, and Attributes - Introducing Geographic Information Systems with ArcGIS - page 411

Extract tool chest. Selection By Attributes is nothing new to you. The difference here is that you will make
an entirely new geodatabase feature class or shapefile based wholly on the selected features and records.

Let's assume that you are trying to find the appropriate polygons for the Wildcat Boat problem. Without
being rigorous, consider a query like the one that follows, made to the composite table that includes land
use, soil suitability, sewer buffers, and stream buffers. You might use Extract to make a feature class of the
polygons where:

LANDUSE = “Brushland”

AND

SOIL_SUITABILITY = “Fair” OR SOIL_SUITABILITY = “Good”

AND

DISTANCE_TO_SEWERS <= 300

AND

DISTANCE_FROM_STREAMS > 20

In summary, then, the EXTRACT Wizard produces a feature class Y from a feature class X, by extracting
features based on their attribute values. EXTRACT works very much like building a query to select
records in a table (e.g., AREA >= 500 AND COLOR = 'Green').

But instead of simply highlighting records in a table (and the corresponding features on the map),
EXTRACT creates an entirely new dataset (Y) consisting of selected records.

The way to use EXTRACT is, once you have constructed (by repeated buffering and overlaying, using
ArcToolbox), a feature class (A) that contains all the features that those processes produce, you then
extract just those features that meet your criteria, to make feature class B.

The concepts in this Overview pretty much cover the sort of geographic data analysis that is created
by deriving feature classes from other feature classes. There are, of course, a lot of data management
commands that go along with this form of analysis. Also, there are several other types of GIS analysis—
geostatistical for one, network for another—covered in Chapter 9.

In the following Step-by-Step section, you will apply the buffer, overlay, and extraction principles
and tools.

Finally, in the Step-by-Step section of this chapter, I introduce the Model Builder, which is one way to link
and automate the processes in GIS analysis. By building a model:

You can document the flow through the processes of a project.

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You can modify those processes easily, change processes, change the inputs to the processes, and so
on, in a friendly graphical environment.

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You can have the computer repeat some or all of the processes with trivial effort on your part.

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