terminology(1)	       Grass User's Manual	   terminology(1)



GRASS 5 Terminology


       LOCATION:  This	is  the  name  of an available geographic
       location.


       MAPSET:	 Every GRASS session runs under  the  name  of	a
       MAPSET.	A MAPSET may be a geographical subset or as large
       as the parent LOCATION.	Technically they are  subdirecto-
       ries  under  any location. In a networked environment with
       several users working within the  same  location,  mapsets
       play  a special role. Users may only select (and thus mod-
       ify) a mapset that they own (i.e., have created). However,
       data  in  all  mapsets for a given location can be read by
       anyone (unless prevented by UNIX  file  permissions).  The
       "PERMANENT"  mapset  usually  contains  the read-only base
       maps like the elevation model, while the  other	locations
       are readable and writable by their owners. The "PERMANENT"
       mapset also contains some information about  the  location
       itself that is not found in other mapsets (projection info
       etc.), thus it must exist in every location.


       DATABASE: This is the unix directory containing	the  geo-
       graphic LOCATTONS (also called GISDBASE)


       REGION: The REGION may be the entire area or subset of the
       chosen LOCATION.


       WINDOW: see REGION


       CELL DATA TYPE: a raster map from INTEGER type (whole num-
       bers only)


       FCELL  DATA TYPE: a raster map from FLOAT type (4 bytes, 6
       digits precision)


       DCELL DATA TYPE: a raster map from DOUBLE type  (8  bytes,
       10 digits precision)


       NULL:  represents  "no data" in raster maps, to be distin-
       guished from 0 (zero) data value


       INTEGER MAP: see CELL DATA TYPE


       FLOAT MAP: see FCELL DATA TYPE


       DOUBLE MAP: see DCELL DATA TYPE


       CATEGORY NUMBER: A numerical value for a map feature (e.g.
       road number).  Also sometimes called CATEGORY VALUE.


       CATEGORY  LABEL:  A text attribute for a map feature (e.g.
       road name).


       Both CATEGORY NUMBER and CATEGORY LABEL are related to the
       dig_cats/  file.  The internal vector ID is different from
       this.


       Inofficial proposal for 5.1 (to be discussed): Since there
       is  some  confusion about the therm "category numbers" and
       "category labels", there is the suggestion to change these
       two  terms  to  common  GIS  vocabulary for GRASS 5.1: 5.0
       5.1 category number  ->	index		#  numeric  cate-
       gory label   ->	attribute	# text


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GRASS 5.0					   terminology(1)
