helptext(1grass) GRASS GIS User's Manual helptext(1grass)
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 con-
sulting 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 man-
ager 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 geo-
graphical 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 subdi-
rectory. 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 avail-
able 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 ex-
ists 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 si-
multaneous 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 documen-
tation.
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 re-
moved by the owner of the PERMANENT MAPSET; however, they can be ac-
cessed, 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 coordi-
nate 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 cur-
rently 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 https://grass.osgeo.org/download/data/
and the compressed data package(s) extracted into this new database di-
rectory.
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 Wiz-
ard" 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 dis-
play 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 inter-
face. For a first time startup, the following steps have to be fol-
lowed:
1 Create the GRASS GIS database directory (with a file manager; or
on command line: mkdir /home/user/grassdata
2 Create a new location, including it’s default PERMANENT mapset,
without entering the new location:
• Using an EPSG code:
grass78 -e -c EPSG:32630 /home/user/grassdata/mylocation
• Using a georeferenced raster or vector file:
grass78 -e -c MyGeoReferenceFile.tif /home/user/grassdata/my-
location
3 Create new mapset within the new location and launch GRASS GIS
within that mapset:
grass78 -c /home/user/grassdata/mylocation/mymapset
Further Reading
Please have a look at the GRASS GIS web site for tutorials and books:
https://grass.osgeo.org/learn/.
See also
GRASS GIS 7 Reference Manual
GRASS GIS 7 startup program manual page
List of EPSG codes (Database of worldwide coordinate systems)
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