The GIS Procedure

Overview: GIS Procedure

The GIS procedure creates and maintains the spatial databases that are used by SAS/GIS software. A SAS/GIS spatial database consists of the following elements:
  • SAS data sets that contain the coordinates and identifying information for the spatial features.
  • a spatial entry (a SAS catalog entry of type GISSPA) that identifies which SAS data sets contain spatial information. The spatial entry also stores the following elements:
    • composites that define how the variables in the spatial data are used
    • names of the polygonal indexes that define the boundaries of area layers for the map
    • a lattice hierarchy that defines which features in the spatial data enclose or are enclosed by other features (the relationships among the polygonal variables)
    • information about the projection method that is used for the stored spatial data
    A spatial entry alternatively can contain references to two or more other spatial entries that have been merged into a single spatial database.
  • a coverage entry (a SAS catalog entry of type GISCOVER) that selects a subset of the spatial data that is available for display in a map.
  • one or more layer entries (SAS catalog entries of type GISLAYER) that identify features that have common characteristics and specify how they are displayed as layers in the map.
  • a map entry (a SAS catalog entry of type GISMAP) that specifies which layers from a particular coverage are included in a map. The map entry also stores the following information:
    • the names of attribute data sets that are associated with the map, along with definitions of how the attribute data is linked to the spatial data
    • the name of a SAS data set that contains labels for map features
    • definitions of GIS actions that can be performed when map features are selected
    • definitions for map legends
    • values for display and projection options
Note: The task of creating new SAS/GIS spatial databases from spatial data in other formats can also be performed interactively by using the GIS Spatial Data Importing window or programmatically by using the SAS/GIS batch import process.