1helptext(1) Grass User's Manual helptext(1)
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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).
15
17 For text-based startup see below.
18 After launching GRASS GIS, the startup screen will open:
20 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.
27 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.
34 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.
38 See to directly download a sample LOCATION into the DATABASE.
40 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).
44 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.
52 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.
58 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.
64
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.
71 Fig. 1: GRASS GIS 7 location structure
73 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.
83 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.
87 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.
105
107 To create the GRASS database:
108 1 Find a place on your disk where you have write access and that
110 has enough disk space to hold your spatial data.
111 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).
115 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.
120 Now you are ready to select a sample dataset in the GRASS GIS startup
122 screen (see above) and start the session.
123
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.
130 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.
136 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).
142
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:
147 1 Create a GRASS GIS database as explained above.
149 2 Create a new location, including it’s default PERMANENT mapset,
151 without entering the new location:
152 · Using an EPSG code:
154 grass74 -e -c EPSG:32630 /home/user/grassdata/mylocation
155 · Using a georeferenced raster or vector file:
157 grass74 -e -c MyGeoReferenceFile.tif /home/user/grassdata/mylo‐
158 cation
159 3 Create new mapset within the new location and launch GRASS GIS
161 within that mapset:
162 grass74 -c /home/user/grassdata/mylocation/mymapset
163
165 Please have a look at the GRASS GIS web site for tutorials and books:
166 http://grass.osgeo.org/documentation/.
167
169 GRASS GIS 7 Reference Manual
170 GRASS GIS 7 startup program manual page
171 List of EPSG codes (Database of worldwide coordinate systems)
173 Last changed: $Date: 2017-12-11 21:08:09 +0100 (Mon, 11 Dec 2017) $
175 Main index | Topics index | Keywords index | Graphical index | Full
177 index
178 © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
180GRASS 7.4.4 helptext(1)