GPROJECT Procedure

About the Input Map Data Set

Input Map Data Set Variables

The input map data set must be in a SAS data set format (see About Map Data Sets), and it must contain these variables:

a numeric variable named X that contains the longitude coordinates of the map boundary points.
a numeric variable named Y that contains the latitude coordinates of the map boundary points.
one or more identification variables that uniquely identify the unit areas in the map. These variables are listed in the ID statement.

The X and Y variables contain the values that are to be projected.

In addition, the input map data set can also contain these variables:

a numeric variable named SEGMENT that distinguishes nonconterminous segments of the unit areas.
a numeric variable named DENSITY that can be used to affect the output from PROC GPROJECT. See Clipping Map Data Sets for more information.

Other variables in the input map data set do not affect the GPROJECT procedure.

Input Map Data Sets That Contain Only Unprojected Values

The following is a list of all of the data sets supplied by SAS that contain X and Y variables whose values are unprojected:

CANADA3
CANADA4
COUNTIES
COUNTY
STATES

See Using Default Projection Specifications for an illustration of this type of input map data set and the variables that it contains.

Note: Projection is appropriate for map data sets in which the X and Y variable values represent longitude and latitude. Some of the map data sets that are supplied with SAS/GRAPH have already been projected; such data set should not be projected again.

Input Map Data Sets That Contain Both Projected and Unprojected Values

All GfK Marketing and most traditional map data sets contain both sets of variables (X, Y and LONG, LAT) for projected and unprojected maps. In these cases, the X and Y variables produce a projected map so you do not need to use the GPROJECT procedure. However, you might want to use the LONG and LAT variables to reproject the map using a different projection type. The LATLON option specifies that the GPROJECT procedure uses the LONG and LAT variables instead of X and Y.

For additional information about the supplied SAS/GRAPH map data sets, see About Map Data Sets and the METAMAPS data set in your maps data set directory.