A projection is required
to represent spherical features like the earth's surface on a
flat medium like a display screen or printed page.
SAS/GIS software
supports a wide variety of projection methods. However, it assumes
by default that the coordinate values in newly imported spatial data
are arbitrary Cartesian (X/Y) values. Exceptions to this are TIGER
and DYNAMAP files, for which
SAS/GIS software assumes latitude and
longitude degrees. However,
the coordinates in the MAPS.COUNTY or MAPSSAS.COUNTY map data set
are actually latitude and longitude values in radians.
As a result, the initial
Carolinas map in Initial Display of Imported SAS/GRAPH Map is elongated and reversed right-to-left.
To change the projection
system that is used for the spatial data, use the
GIS
Projection Options window. Open the
GIS Projection
Options window with the following selections from the
GIS
Map window's menu bar:
ToolsMap PropertiesProjections.
In the
GIS
Projection Options window,
Storage Projection
System specifies the system that is used to interpret
the stored spatial data.
Display Projection System specifies
the system that is used to project the interpreted spatial data in
the
GIS Map window. Use the drop-down arrows
to select
Lat/Lon
for both
Storage
Projection System and
Display Projection
System. Also, in the storage system parameters, select
W
for
Hemisphere and
1
for
the
Units Multiplier. Select
Close to
close the
GIS Projection Options window and
apply the new projection specifications.
Note: This example uses the same
projection system for the storage projection system and the display
projection system. It is not required that the two use the same projection
system unless the storage projection system is arbitrary Cartesian
data.
The spatial data is
reloaded into the
GIS Map window by using
the new projection systems. The resulting output of the projected
version of the map is shown in the following display.
Changing the Initial Projection