1r.grow(1) GRASS GIS User's Manual r.grow(1)
2
6 r.grow - Generates a raster map layer with contiguous areas grown by
7 one cell.
8
10 raster, distance, proximity
11
13 r.grow
14 r.grow --help
15 r.grow [-m] input=name output=name [radius=float] [metric=string]
16 [old=integer] [new=integer] [--overwrite] [--help] [--verbose]
17 [--quiet] [--ui]
18 Flags:
20 -m
21 Radius is in map units rather than cells
22 --overwrite
24 Allow output files to overwrite existing files
25 --help
27 Print usage summary
28 --verbose
30 Verbose module output
31 --quiet
33 Quiet module output
34 --ui
36 Force launching GUI dialog
37 Parameters:
39 input=name [required]
40 Name of input raster map
41 output=name [required]
43 Name for output raster map
44 radius=float
46 Radius of buffer in raster cells
47 Default: 1.01
48 metric=string
50 Metric
51 Options: euclidean, maximum, manhattan
52 Default: euclidean
53 old=integer
55 Value to write for input cells which are non-NULL (-1 => NULL)
56 new=integer
58 Value to write for "grown" cells
59
61 r.grow adds cells around the perimeters of all areas in a user-speci‐
62 fied raster map layer and stores the output in a new raster map layer.
63 The user can use it to grow by one or more than one cell (by varying
64 the size of the radius parameter), or like r.buffer, but with the
65 option of preserving the original cells (similar to combining r.buffer
66 and r.patch).
67 If radius is negative,r.grow shrinks areas by removing cells around the
69 perimeters of all areas.
70
72 The user has the option of specifying three different metrics which
73 control the geometry in which grown cells are created, (controlled by
74 the metric parameter): Euclidean, Manhattan, and Maximum.
75 The Euclidean distance or Euclidean metric is the "ordinary" distance
77 between two points that one would measure with a ruler, which can be
78 proven by repeated application of the Pythagorean theorem. The formula
79 is given by:
80 d(dx,dy) = sqrt(dx^2 + dy^2)
81 Cells grown using this metric would form isolines of distance that are
82 circular from a given point, with the distance given by the radius.
83 The Manhattan metric, or Taxicab geometry, is a form of geometry in
85 which the usual metric of Euclidean geometry is replaced by a new met‐
86 ric in which the distance between two points is the sum of the (abso‐
87 lute) differences of their coordinates. The name alludes to the grid
88 layout of most streets on the island of Manhattan, which causes the
89 shortest path a car could take between two points in the city to have
90 length equal to the points’ distance in taxicab geometry. The formula
91 is given by:
92 d(dx,dy) = abs(dx) + abs(dy)
93 where cells grown using this metric would form isolines of distance
94 that are rhombus-shaped from a given point.
95 The Maximum metric is given by the formula
97 d(dx,dy) = max(abs(dx),abs(dy))
98 where the isolines of distance from a point are squares.
99 If there are two cells which are equal candidates to grow into an empty
101 space, r.grow will choose the northernmost candidate; if there are mul‐
102 tiple candidates with the same northing, the westernmost is chosen.
103
105 In this example, the lakes map in the North Carolina sample dataset
106 location is buffered:
107 g.region raster=lakes -p
108 # the lake raster map pixel resolution is 10m
109 r.grow input=lakes output=lakes_grown_100m radius=10
110 Shrinking instead of growing:
111 g.region raster=lakes -p
112 # the lake raster map pixel resolution is 10m
113 r.grow input=lakes output=lakes_shrunk_100m radius=-10
114
116 r.buffer, r.grow.distance, r.patch
117 Wikipedia Entry: Euclidean Metric
119 Wikipedia Entry: Manhattan Metric
120
122 Marjorie Larson, U.S. Army Construction Engineering Research Laboratory
123 Glynn Clements
125
127 Available at: r.grow source code (history)
128 Main index | Raster index | Topics index | Keywords index | Graphical
130 index | Full index
131 © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
133GRASS 7.8.5 r.grow(1)