1r.mask(1)                   GRASS GIS User's Manual                  r.mask(1)
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NAME

6       r.mask  - Creates a MASK for limiting raster operation.
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KEYWORDS

9       raster, mask
10

SYNOPSIS

12       r.mask
13       r.mask --help
14       r.mask   [-ir]    [raster=name]     [maskcats=string]     [vector=name]
15       [layer=string]     [cats=range]     [where=sql_query]     [--overwrite]
16       [--help]  [--verbose]  [--quiet]  [--ui]
17
18   Flags:
19       -i
20           Create inverse mask
21
22       -r
23           Remove existing mask (overrides other options)
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25       --overwrite
26           Allow output files to overwrite existing files
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28       --help
29           Print usage summary
30
31       --verbose
32           Verbose module output
33
34       --quiet
35           Quiet module output
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37       --ui
38           Force launching GUI dialog
39
40   Parameters:
41       raster=name
42           Name of raster map to use as mask
43
44       maskcats=string
45           Raster values to use for mask
46           Format: 1 2 3 thru 7 *
47           Default: *
48
49       vector=name
50           Name of vector map to use as mask
51           Or data source for direct OGR access
52
53       layer=string
54           Layer number or name (vector)
55           Vector  features can have category values in different layers. This
56           number determines which layer to use. When  used  with  direct  OGR
57           access this is the layer name.
58           Default: 1
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60       cats=range
61           Category values (vector)
62           Example: 1,3,7-9,13
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64       where=sql_query
65           WHERE conditions of SQL statement without ’where’ keyword (vector)
66           Example: income < 1000 and population >= 10000
67

DESCRIPTION

69       r.mask  - Facilitates creation of a raster "MASK" map to control raster
70       operations.
71
72       The MASK is only applied when reading an existing GRASS raster map, for
73       example when used in a module as an input map.  The MASK will block out
74       certain areas of a raster map from analysis and/or display, by "hiding"
75       them  from sight of other GRASS modules. Data falling within the bound‐
76       aries of the MASK can be modified and  operated  upon  by  other  GRASS
77       raster  modules; data falling outside the MASK is treated as if it were
78       NULL.
79
80       Because the MASK is actually only a reclass map named "MASK", it can be
81       copied,  renamed,  removed, and used in analyses, just like other GRASS
82       raster map layers.  The user should be aware that  a  MASK  remains  in
83       place  until  a  user  renames  it  to  something other than "MASK", or
84       removes it using "r.mask -r" or g.remove.
85
86       Grid cells in the MASK map containing 0 or NULL will replace data  with
87       NULL,  while  cells  containing  other  values  will allow data to pass
88       through unaltered.
89
90       To restore raster operations to normal (i.e., all cells of the  current
91       region),  remove  the  MASK file by setting the -r remove MASK flag. In
92       this case, a dummy value must also be given for the input parameter.  A
93       MASK  also  can  be  removed by using g.remove or by renaming it to any
94       other name with g.rename.
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NOTES

97       The above method for specifying a  "mask"  may  seem  counterintuitive.
98       Areas  inside  the  MASK are not hidden; areas outside the MASK will be
99       ignored until the MASK file is removed.
100
101       The MASK is read as an integer  map.  If  MASK  is  actually  a  float‐
102       ing-point map, the values will be converted to integers using the map’s
103       quantisation rules (this  defaults  to  round-to-nearest,  but  can  be
104       changed with r.quant).
105
106       r.mask  uses  r.reclass  to  create  a  reclassification of an existing
107       raster map and name it MASK. A reclass map takes up less space, but  is
108       affected  by  any  changes to the underlying map from which it was cre‐
109       ated.  The user can select category values from the input raster to use
110       in the MASK with the maskcats parameter; if r.mask is run from the com‐
111       mand line, the category values listed in maskcats must be  quoted  (see
112       example below).
113
114       Somewhat  similar program functions to those performed by r.mask can be
115       done using r.mapcalc, g.region, and other commands.
116

EXAMPLES

118       The examples are based on the North Carolina sample dataset.
119
120       Create a raster mask, for contraining  the  calculation  of  univariate
121       statistics of the elevation values for "lakes":
122       # set computation region to lakes raster map
123       g.region raster=lakes -p
124       # use lakes as MASK
125       r.mask raster=lakes
126       # get statistics for elevation pixels of lakes:
127       r.univar elevation
128       Remove the raster mask ("MASK" map) with the -r flag:
129       r.mask -r
130       Creating  a  mask from selected categories in the North Carolina ’geol‐
131       ogy_30m’ raster map:
132       g.region raster=geology_30m -p
133       r.category geology_30m
134       d.mon wx0
135       d.rast geology_30m
136       r.mask raster=geology_30m maskcats="217 thru 720"
137       d.mon wx0
138       d.rast geology_30m
139

SEE ALSO

141        g.region, r.mapcalc, r.reclass, g.remove, g.rename
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AUTHOR

144       Michael Barton, Arizona State University
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SOURCE CODE

147       Available at: r.mask source code (history)
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149       Main index | Raster index | Topics index | Keywords index  |  Graphical
150       index | Full index
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152       © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
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156GRASS 7.8.5                                                          r.mask(1)
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