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GRASS GIS Quickstart

Geographic Resources Analysis Support System

       GRASS  GIS,  commonly referred to as GRASS (Geographic Resources Analysis Support System),
       is a free Geographic Information System (GIS) software used for geospatial data management
       and   analysis,   image   processing,  graphics/maps  production,  spatial  modeling,  and
       visualization. GRASS GIS is currently used in academic and commercial settings around  the
       world,  as  well  as by many governmental agencies and environmental consulting companies.
       GRASS GIS is an official project of the Open Source Geospatial Foundation (OSGeo).

1. Graphical startup of GRASS GIS

       For text-based startup see below.

       After launching GRASS GIS, the startup screen will open:

   Selecting the GIS Database directory
       GRASS data are stored in a directory referred to as  DATABASE  (also  called  "GISDBASE").
       This directory has to be created with a file manager or the mkdir command, before starting
       to work with GRASS.  Within this DATABASE, the projects are  organized  by  project  areas
       stored in subdirectories called LOCATIONs.

   Selecting the LOCATION (a project)
       A  LOCATION  is  defined  by  its  coordinate  system,  map  projection  and  geographical
       boundaries. The subdirectories and files defining a  LOCATION  are  created  automatically
       when  GRASS  is  started the first time with a new LOCATION. It is important to understand
       that each projection stays in its own LOCATION.

       See the "Location Wizard"  to easily create a new LOCATION from scratch  from  a  geocoded
       file, by defining the parameters or by selecting the corresponding EPSG projection code.

       See  to directly download a sample LOCATION into the DATABASE.

   Selecting the MAPSET (a subproject)
       Each  LOCATION can have many MAPSETs. Each MAPSET is a LOCATION’s subdirectory. New MAPSET
       can be added at GRASS startup (see related button).

   Location Wizard
       The "Location Wizard" let’s you easily create a new LOCATION. You will be guided through a
       series of dialogues to browse and select predefined projections (also via EPSG code) or to
       define  individual  projections.  You  can  also  create  new  LOCATION  easily   from   a
       georeferenced  data  file  (e.g., SHAPE file or GeoTIFF, see below).  Find below also some
       rules to define the default raster resolution for a new LOCATION.

   Download a sample LOCATION
       In the "Location Wizard" there is also a Download  button  that  allows  you  to  directly
       download  a ready-to-use LOCATION into the DATABASE. You can choose among different sample
       LOCATIONS that are currently available at the Download section in the GRASS GIS website.

   Start GRASS
       Once you have selected an existing LOCATION/MAPSET or defined a new  one,  you  can  enter
       GRASS.  The  graphical  user interface wxGUI will open and provide you with a menu system,
       map visualization tool, digitizer, and more.

2. Background: GRASS GIS Location structure

       A LOCATION is simply a set of directories which contains the  GRASS  data  of  a  project.
       Within  each  LOCATION,  a  mandatory  "PERMANENT" MAPSET exists which contains projection
       information and some more definitions. It can be used to store the base cartography in  it
       as "PERMANENT" is visible to all users accessing a LOCATION.

       Fig. 1: GRASS GIS 7 location structure

   Creating and maintaining MAPSETs
       One motivation to maintain different MAPSETs is to store maps related to project issues or
       subregions. Another motivation is to support simultaneous access of several users  to  the
       map  layers  stored  within the same LOCATION, i.e. teams working on the same project. For
       teams, a centralized GRASS DATABASE would be defined in a shared network file system (e.g.
       NFS).  Besides  access  to his/her own MAPSET, each user can also read map layers in other
       users’ MAPSETs, but s/he can modify or remove only the map layers in his/her own MAPSET.

       You can learn more about mapsets and how to seamlessly access maps found in another MAPSET
       of the same LOCATION in the g.mapsets documentation.

   The role of the "PERMANENT" MAPSET
       When  creating  a  new  LOCATION,  GRASS GIS automatically creates a special MAPSET called
       PERMANENT where the core data for the project can be stored. Data in the PERMANENT  MAPSET
       can only be added, modified or removed by the owner of the PERMANENT MAPSET; however, they
       can be accessed, analyzed, and copied into their  own  MAPSET  by  the  other  users.  The
       PERMANENT  MAPSET  is useful for providing general spatial data (e.g. an elevation model),
       accessible but write-protected to all users who are working in the same  LOCATION  as  the
       database  owner.   To manipulate or add data to PERMANENT, the owner would start GRASS and
       choose the relevant LOCATION and the PERMANENT MAPSET.   This  mapset  also  contains  the
       DEFAULT_WIND  file,  which  holds  the  default  region boundary coordinate values for the
       LOCATION (which all users will inherit when they start using the database).  Additionally,
       in all mapsets a WIND file is kept, for storing the current boundary coordinate values and
       the currently selected raster resolution.  Users have the option of switching back to  the
       default region at any time.

3. Creating a GRASS Database with Sample Data

       To create the GRASS database:

       1      Find  a  place  on  your  disk where you have write access and that has enough disk
              space to hold your spatial data.

       2      Create a subdirectory that will hold the general GRASS database (e.g. using a  file
              manager or with mkdir /data/grassdata or mkdir /home/yourlogin/grassdata).

       Sample  data  such  as  the  "North  Carolina"  or  the "Spearfish" sample datasets may be
       downloaded  from  http://grass.osgeo.org/download/sample-data/  and  the  compressed  data
       package(s) extracted into this new database directory.

       Now  you  are ready to select a sample dataset in the GRASS GIS startup screen (see above)
       and start the session.

4. Creating a New Location with the Location Wizard

       The wxGUI graphical user interface provides a graphical "Location Wizard" which  lets  you
       easily  create  a  new  LOCATION  for  own  data.  You  will be guided through a series of
       dialogues to browse and select predefined projections (also via EPSG code)  or  to  define
       individual  projections.  The rules to define the resolution as described above also apply
       here.

       Hint: You can create new LOCATION easily from a georeferenced data file (e.g., SHAPE  file
       or  GeoTIFF file with the related metadata properly included).  In this case you are asked
       whether the data itself should be imported into the new LOCATION. The  default  region  is
       then set to match imported map and the GRASS GIS session is opened.

       After  defining  new LOCATION, wxGUI starts automatically.  If data were already imported,
       you can add them into the Layer Manager now and display them. If your  LOCATION  is  empty
       you  can  import your data from the menu: Go to "File" -> "Import raster/vector data" (see
       also the related Wiki page on Importing data).

5. Text-based startup and location creation

       GRASS GIS can be run entirely without using the graphical user  interface.   For  a  first
       time startup, the following steps have to be followed:

       1      Create a GRASS GIS database as explained above.

       2      Create  a  new  location, including it’s default PERMANENT mapset, without entering
              the new location:

           ·   Using an EPSG code:
               grass76 -e -c EPSG:32630 /home/user/grassdata/mylocation

           ·   Using a georeferenced raster or vector file:
               grass76 -e -c MyGeoReferenceFile.tif /home/user/grassdata/mylocation

       3      Create new mapset within the new location and launch GRASS GIS within that mapset:
              grass76 -c /home/user/grassdata/mylocation/mymapset

Further Reading

       Please  have  a  look  at  the   GRASS   GIS   web   site   for   tutorials   and   books:
       http://grass.osgeo.org/documentation/.

See also

        GRASS GIS 7 Reference Manual
       GRASS GIS 7 startup program manual page

       List of EPSG codes (Database of worldwide coordinate systems)

       Last changed: $Date: 2018-08-31 17:01:15 +0200 (Fri, 31 Aug 2018) $

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