Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Deriving Feature Classes by Selecting Attributes: Extraction

You have perhaps buffered some points, lines, and polygons, and have the results as feature classes. You have overlaid these buffers on some other polygon feature classes. What you now have is a feature class that has dozens, hundreds, maybe even thousands of polygons. That feature class also has an attribute table with a list of fields as long as your arm, since it consists of almost all the attributes of the constituents tables. Now it is time to make a feature class that consists only of those polygons that meet your requirements. You do this by writing a query that will be processed by the Select tool, within the 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 ...