Using ArcCatalog

Defining a
shapefile’s
coordinate
system
A shapefile often doesn’t have
any information defining which
coordinate system was used to
define its features. In this case,
the Shape column’s Spatial
Reference property will be
unknown or assumed geographic.
If the features’ bounding
coordinates are within the
range of -180 and 180 in the x
direction and -90 and 90 in the y
direction, ArcGIS software
assumes the data to be geographic
and its datum to be
NAD27. You can work with
shapefiles even if their coordinate
system hasn’t been
defined, but you may not be
able to take advantage of all the
available functionality. For
example, you may be unable to
add the shapefile to some maps,
and its automatically created
metadata will be incomplete.
You can define a shapefile’s
coordinate system in
ArcCatalog in several ways.
You can select one of the
predefined coordinate systems
provided with ArcCatalog,
import the coordinate system
parameters used by another
data source, or define a new, u
Defining a shapefile’s
coordinate system
1. Click the shapefile whose
coordinate system you want
to define.
2. Click the File menu and click
Properties.
3. Click the Fields tab.
4. Click the Shape column in
the column list.
5. In the Field Properties list
below, click the ellipsis button
(...) next to the Spatial
Reference property.
6. In the Spatial Reference
Properties dialog box, click
Select, then choose a
predefined coordinate
system.
Or, click Import and choose
the data source whose
coordinate system parameters
you want to copy.
Or, click New, click Geographic
or Projected, and
define a new, custom
coordinate system.
7. Click OK in the Spatial
Reference Properties dialog
box. u
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184 USING ARCCATALOG