1helptext(1)                   Grass User's Manual                  helptext(1)
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GRASS GIS Quickstart

Geographic Resources Analysis Support System

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

17       For text-based startup see below.
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19       After launching GRASS GIS, the startup screen will open:
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21   Selecting the GIS Database directory
22       GRASS data are stored in a directory  referred  to  as  DATABASE  (also
23       called  "GISDBASE").  This directory has to be created with a file man‐
24       ager or the mkdir command, before starting to work with GRASS.   Within
25       this  DATABASE,  the  projects are organized by project areas stored in
26       subdirectories called LOCATIONs.
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28   Selecting the LOCATION (a project)
29       A LOCATION is defined by its coordinate system, map projection and geo‐
30       graphical  boundaries. The subdirectories and files defining a LOCATION
31       are created automatically when GRASS is started the first time  with  a
32       new  LOCATION. It is important to understand that each projection stays
33       in its own LOCATION.
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35       See the "Location Wizard"  to easily create a new LOCATION from scratch
36       from  a  geocoded  file, by defining the parameters or by selecting the
37       corresponding EPSG projection code.
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39       See  to directly download a sample LOCATION into the DATABASE.
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41   Selecting the MAPSET (a subproject)
42       Each LOCATION can have many MAPSETs. Each MAPSET is a LOCATION’s subdi‐
43       rectory. New MAPSET can be added at GRASS startup (see related button).
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45   Location Wizard
46       The  "Location Wizard" let’s you easily create a new LOCATION. You will
47       be guided through a series of dialogues to browse and select predefined
48       projections  (also  via EPSG code) or to define individual projections.
49       You can also create new LOCATION easily from a georeferenced data  file
50       (e.g.,  SHAPE  file or GeoTIFF, see below).  Find below also some rules
51       to define the default raster resolution for a new LOCATION.
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53   Download a sample LOCATION
54       In the "Location Wizard" there is also a Download  button  that  allows
55       you to directly download a ready-to-use LOCATION into the DATABASE. You
56       can choose among different sample LOCATIONS that are  currently  avail‐
57       able at the Download section in the GRASS GIS website.
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59   Start GRASS
60       Once  you  have  selected  an existing LOCATION/MAPSET or defined a new
61       one, you can enter GRASS. The graphical user interface wxGUI will  open
62       and  provide you with a menu system, map visualization tool, digitizer,
63       and more.
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2. Background: GRASS GIS Location structure

66       A LOCATION is simply a set of directories which contains the GRASS data
67       of  a  project.  Within  each  LOCATION, a mandatory "PERMANENT" MAPSET
68       exists which contains projection information and some more definitions.
69       It  can  be  used to store the base cartography in it as "PERMANENT" is
70       visible to all users accessing a LOCATION.
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72       Fig. 1: GRASS GIS 7 location structure
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74   Creating and maintaining MAPSETs
75       One motivation to maintain different MAPSETs is to store  maps  related
76       to  project  issues  or  subregions.  Another  motivation is to support
77       simultaneous access of several users to the map  layers  stored  within
78       the same LOCATION, i.e. teams working on the same project. For teams, a
79       centralized GRASS DATABASE would be defined in a  shared  network  file
80       system  (e.g. NFS). Besides access to his/her own MAPSET, each user can
81       also read map layers in other users’ MAPSETs, but s/he  can  modify  or
82       remove only the map layers in his/her own MAPSET.
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84       You  can  learn  more  about  mapsets and how to seamlessly access maps
85       found in another MAPSET of the same LOCATION in the g.mapsets  documen‐
86       tation.
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88   The role of the "PERMANENT" MAPSET
89       When creating a new LOCATION, GRASS GIS automatically creates a special
90       MAPSET called PERMANENT where the core data  for  the  project  can  be
91       stored.  Data  in  the  PERMANENT MAPSET can only be added, modified or
92       removed by the owner of the PERMANENT  MAPSET;  however,  they  can  be
93       accessed,  analyzed,  and  copied  into  their  own MAPSET by the other
94       users. The PERMANENT MAPSET is useful  for  providing  general  spatial
95       data  (e.g.  an elevation model), accessible but write-protected to all
96       users who are working in the same LOCATION as the database  owner.   To
97       manipulate  or  add  data to PERMANENT, the owner would start GRASS and
98       choose the relevant LOCATION and the  PERMANENT  MAPSET.   This  mapset
99       also  contains  the  DEFAULT_WIND  file, which holds the default region
100       boundary coordinate values for  the  LOCATION  (which  all  users  will
101       inherit  when  they  start  using  the  database). Additionally, in all
102       mapsets a WIND file is kept, for storing the current  boundary  coordi‐
103       nate  values  and the currently selected raster resolution.  Users have
104       the option of switching back to the default region at any time.
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3. Creating a GRASS Database with Sample Data

107       To create the GRASS database:
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109       1      Find a place on your disk where you have write access  and  that
110              has enough disk space to hold your spatial data.
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112       2      Create  a subdirectory that will hold the general GRASS database
113              (e.g. using a file manager  or  with  mkdir  /data/grassdata  or
114              mkdir /home/yourlogin/grassdata).
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116       Sample  data  such  as  the  "North Carolina" or the "Spearfish" sample
117       datasets may be  downloaded  from  http://grass.osgeo.org/download/sam
118       ple-data/  and  the  compressed data package(s) extracted into this new
119       database directory.
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121       Now you are ready to select a sample dataset in the GRASS  GIS  startup
122       screen (see above) and start the session.
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4. Creating a New Location with the Location Wizard

125       The  wxGUI graphical user interface provides a graphical "Location Wiz‐
126       ard" which lets you easily create a new LOCATION for own data. You will
127       be guided through a series of dialogues to browse and select predefined
128       projections (also via EPSG code) or to define  individual  projections.
129       The rules to define the resolution as described above also apply here.
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131       Hint: You can create new LOCATION easily from a georeferenced data file
132       (e.g., SHAPE file or GeoTIFF file with the  related  metadata  properly
133       included).   In  this case you are asked whether the data itself should
134       be imported into the new LOCATION. The default region is  then  set  to
135       match imported map and the GRASS GIS session is opened.
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137       After  defining new LOCATION, wxGUI starts automatically.  If data were
138       already imported, you can add them into the Layer Manager now and  dis‐
139       play  them. If your LOCATION is empty you can import your data from the
140       menu: Go to "File" -> "Import raster/vector data" (see also the related
141       Wiki page on Importing data).
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5. Text-based startup and location creation

144       GRASS  GIS  can be run entirely without using the graphical user inter‐
145       face.  For a first time startup, the following steps have  to  be  fol‐
146       lowed:
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148       1      Create a GRASS GIS database as explained above.
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150       2      Create  a new location, including it’s default PERMANENT mapset,
151              without entering the new location:
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153           ·   Using an EPSG code:
154               grass74 -e -c EPSG:32630 /home/user/grassdata/mylocation
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156           ·   Using a georeferenced raster or vector file:
157               grass74 -e -c MyGeoReferenceFile.tif /home/user/grassdata/mylo‐
158               cation
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160       3      Create  new  mapset within the new location and launch GRASS GIS
161              within that mapset:
162              grass74 -c /home/user/grassdata/mylocation/mymapset
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Further Reading

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

169        GRASS GIS 7 Reference Manual
170       GRASS GIS 7 startup program manual page
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172       List of EPSG codes (Database of worldwide coordinate systems)
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174       Last changed: $Date: 2017-12-11 21:08:09 +0100 (Mon, 11 Dec 2017) $
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176       Main  index  |  Topics  index | Keywords index | Graphical index | Full
177       index
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179       © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
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183GRASS 7.4.4                                                        helptext(1)
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