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

6       r.grow.distance  - Generates a raster map containing distances to near‐
7       est raster features and/or the value of the nearest non-null cell.
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KEYWORDS

10       raster, distance, proximity
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SYNOPSIS

13       r.grow.distance
14       r.grow.distance --help
15       r.grow.distance  [-mn]   input=name    [distance=name]     [value=name]
16       [metric=string]    [minimum_distance=float]    [maximum_distance=float]
17       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]
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19   Flags:
20       -m
21           Output distances in meters instead of map units
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23       -n
24           Calculate distance to nearest NULL cell
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26       --overwrite
27           Allow output files to overwrite existing files
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29       --help
30           Print usage summary
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32       --verbose
33           Verbose module output
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35       --quiet
36           Quiet module output
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38       --ui
39           Force launching GUI dialog
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41   Parameters:
42       input=name [required]
43           Name of input raster map
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45       distance=name
46           Name for distance output raster map
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48       value=name
49           Name for value output raster map
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51       metric=string
52           Metric
53           Options: euclidean, squared, maximum, manhattan, geodesic
54           Default: euclidean
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56       minimum_distance=float
57           Minimum distance threshold
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59       maximum_distance=float
60           Maximum distance threshold
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DESCRIPTION

63       r.grow.distance generates raster maps representing the distance to  the
64       nearest  non-null cell in the input map and/or the value of the nearest
65       non-null cell.
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NOTES

68       The flag -n calculates the respective pixel distances  to  the  nearest
69       NULL cell.
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71       The user has the option of specifying five different metrics which con‐
72       trol the geometry in which grown cells are created, (controlled by  the
73       metric  parameter):  Euclidean,  Squared,  Manhattan, Maximum, and Geo‐
74       desic.
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76       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.
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84       The Squared metric is the Euclidean distance squared,  i.e.  it  simply
85       omits  the  square-root  calculation. This may be faster, and is suffi‐
86       cient if only relative values are required.
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88       The Manhattan metric, or Taxicab geometry, is a  form  of  geometry  in
89       which  the usual metric of Euclidean geometry is replaced by a new met‐
90       ric in which the distance between two points is the sum of  the  (abso‐
91       lute)  differences  of  their coordinates. The name alludes to the grid
92       layout of most streets on the island of  Manhattan,  which  causes  the
93       shortest  path  a car could take between two points in the city to have
94       length equal to the points’ distance in taxicab geometry.  The  formula
95       is given by:
96       d(dx,dy) = abs(dx) + abs(dy)
97       where  cells  grown  using  this metric would form isolines of distance
98       that are rhombus-shaped from a given point.
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100       The Maximum metric is given by the formula
101       d(dx,dy) = max(abs(dx),abs(dy))
102       where the isolines of distance from a point are squares.
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104       The Geodesic metric is calculated as geodesic distance, to be used only
105       in latitude-longitude locations. It is recommended to use it along with
106       the -m flag in order to output  distances  in  meters  instead  of  map
107       units.
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109       If  minimum_distance  is  given, all cells with a distance smaller than
110       minimum_distance will be set to NULL.
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112       If maximum_distance is given, all cells with  a  distance  larger  than
113       maximum_distance  will  be set to NULL. The resultant output is equiva‐
114       lent to a buffer.
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116       If both minimum_distance and maximum_distance  are  given,  the  result
117       will  be  similar to a doughnut, a restricted belt for a given distance
118       range. All cells outside this distance range will be set to NULL.
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EXAMPLES

121   Distance from the streams network
122       North Carolina sample dataset:
123       g.region raster=streams_derived -p
124       r.grow.distance input=streams_derived distance=dist_from_streams
125       r.colors map=dist_from_streams color=rainbow
126       Euclidean distance from the streams network in meters (map subset)
127       Euclidean distance from the streams network in meters (detail,  numbers
128       shown with d.rast.num)
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130   Distance from sea in meters in latitude-longitude location
131       g.region raster=sea -p
132       r.grow.distance -m input=sea distance=dist_from_sea_geodetic metric=geodesic
133       r.colors map=dist_from_sea_geodetic color=rainbow
134
135       Geodesic distances to sea in meters
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SEE ALSO

138        r.grow, r.distance, r.buffer, r.cost, r.patch
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140        Wikipedia Entry: Euclidean Metric
141       Wikipedia Entry: Manhattan Metric
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AUTHOR

144       Glynn Clements
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SOURCE CODE

147       Available at: r.grow.distance source code (history)
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149       Accessed: Saturday Oct 28 18:17:32 2023
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151       Main  index  | Raster index | Topics index | Keywords index | Graphical
152       index | Full index
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154       © 2003-2023 GRASS Development Team, GRASS GIS 8.3.1 Reference Manual
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158GRASS 8.3.1                                                 r.grow.distance(1)
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