Geography Reference
In-Depth Information
Soils
Streams_buf
Using the four preceding data sets and ArcToolbox
Analysis Tools
Overlay
Union, make a feature
class named Union_mpp in
___IGIS-Arc\ YourInitials \Wildcat_Boat_Data\Wildcat_Boat.mdb\Area_Features.
Union_mpp contains multipart polygons. Look at Union_mpp, clicking a few polygons with the Identify tool.
As you can see, you need to make sure each set of boundaries defines an un-subdivided area.
3. Use the Arctoolbox > Data Management Tools > Features > Multipart To Singlepart tool to
explode Union_mpp into Union_Lc_Se_So_St (for union of landcover, sewer (buffers), soils, and
stream (buffers)). Now note that Identify lights up only single polygons.
4. Carefully, very carefully, examine the table of Union_Lc_Se_So_St. How many polygons are
there? ________. Ignoring, for the moment, the size criterion of 4000 square meters, write
the relevant fields, values, and operators (like
) in the table that follows. These
are the values you must use to extract the sites meeting the criteria. (Some values have
been filled in for you.) Sorting some columns might aid you in determining the
values you need.)
=
,
<>
,
>=
Fields
Operators
Values
(source feature class)
300
Landcover
Sewers_buf
Soils
NoBuild
20
Streams_buf
<>
5. Write the expression that would extract the suitable polygons from Union_Lc_Se_So_St:
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( After writing your expression, check it against Figure 7-23.)
6. Using ArcToolbox > Analysis Tools > Extract > Select with the above expression (be sure to
Verify that it will work), make a feature class from Union_Lc_Se_So_St, which you will name
Sites_A. Look at the attribute table of Sites_A to be sure that the values you specified for the
various fields are proper. How many sites are there? ________
7. Display Sites_A, checking to be sure that it makes sense. Use Identify to look at the areas
to see if they meet the 4000 square meter requirement. You will see some small areas that
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