GMAP Procedure

Map Data Sets Containing X, Y, LONG, and LAT

All of the GfK and most of the traditional map data sets that are provided with SAS/GRAPH software contain four coordinate variables (X, Y, LONG, and LAT). When all four coordinate variables are present, X and Y are always projected values that are used by the SAS/GRAPH procedures (by default). However, you might want to use the LONG and LAT variables to reproject the map using a different projection type. If you need to use the unprojected values that are contained in the LONG and LAT variables, then do the following tasks:
  1. Project the spherical coordinates (latitude and longitude) by using the GPROJECT procedure with its LATLON option, which uses the LAT and LONG variables instead of the X and Y variables.
    Note: LONG and LAT variables in GfK map data sets are in degrees. In traditional map data sets the LONG and LAT variables are in radians or degrees.
  2. Use the output data set from GPROJECT, which now contains Cartesian coordinates, as your input map data set by specifying it in the MAP= value in the GMAP procedure