.TH r.grow.distance 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBr.grow.distance\fR\fR  \- Generates a raster map containing distances to nearest raster features and/or the value of the nearest non\-null cell.
.SH KEYWORDS
raster, distance, proximity
.SH SYNOPSIS
\fBr.grow.distance\fR
.br
\fBr.grow.distance \-\-help\fR
.br
\fBr.grow.distance\fR [\-\fBmn\fR] \fBinput\fR=\fIname\fR  [\fBdistance\fR=\fIname\fR]   [\fBvalue\fR=\fIname\fR]   [\fBmetric\fR=\fIstring\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-m\fR" 4m
.br
Output distances in meters instead of map units
.IP "\fB\-n\fR" 4m
.br
Calculate distance to nearest NULL cell
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of input raster map
.IP "\fBdistance\fR=\fIname\fR" 4m
.br
Name for distance output raster map
.IP "\fBvalue\fR=\fIname\fR" 4m
.br
Name for value output raster map
.IP "\fBmetric\fR=\fIstring\fR" 4m
.br
Metric
.br
Options: \fIeuclidean, squared, maximum, manhattan, geodesic\fR
.br
Default: \fIeuclidean\fR
.SH DESCRIPTION
\fIr.grow.distance\fR generates raster maps representing the
distance to the nearest non\-null cell in the input map and/or the
value of the nearest non\-null cell.
.SH NOTES
The flag \fB\-n\fR calculates the respective pixel distances to the
nearest NULL cell.
.PP
The user has the option of specifying five different metrics which
control the geometry in which grown cells are created, (controlled by
the \fBmetric\fR parameter): \fIEuclidean\fR, \fISquared\fR,
\fIManhattan\fR, \fIMaximum\fR, and \fIGeodesic\fR.
.PP
The \fIEuclidean distance\fR or \fIEuclidean metric\fR is the \(dqordinary\(dq distance
between two points that one would measure with a ruler, which can be
proven by repeated application of the Pythagorean theorem.
The formula is given by:
.br
.nf
\fC
d(dx,dy) = sqrt(dx^2 + dy^2)
\fR
.fi
Cells grown using this metric would form isolines of distance that are
circular from a given point, with the distance given by the \fBradius\fR.
.PP
The \fISquared\fR metric is the \fIEuclidean\fR distance squared,
i.e. it simply omits the square\-root calculation. This may be faster,
and is sufficient if only relative values are required.
.PP
The \fIManhattan metric\fR, or \fITaxicab geometry\fR, is a form of geometry in
which the usual metric of Euclidean geometry is replaced by a new
metric in which the distance between two points is the sum of the (absolute)
differences of their coordinates. The name alludes to the grid layout of
most streets on the island of Manhattan, which causes the shortest path a
car could take between two points in the city to have length equal to the
points\(cq distance in taxicab geometry.
The formula is given by:
.br
.nf
\fC
d(dx,dy) = abs(dx) + abs(dy)
\fR
.fi
where cells grown using this metric would form isolines of distance that are
rhombus\-shaped from a given point.
.PP
The \fIMaximum metric\fR is given by the formula
.br
.nf
\fC
d(dx,dy) = max(abs(dx),abs(dy))
\fR
.fi
where the isolines of distance from a point are squares.
.PP
The \fIGeodesic metric\fR is calculated as geodesic distance, to
be used only in latitude\-longitude locations. It is recommended
to use it along with the \fI\-m\fR flag in order to output
distances in meters instead of map units.
.SH EXAMPLES
.SS Distance from the streams network
North Carolina sample dataset:
.br
.nf
\fC
g.region raster=streams_derived \-p
r.grow.distance input=streams_derived distance=dist_from_streams
r.colors map=dist_from_streams color=rainbow
\fR
.fi
.br
\fIEuclidean distance from the streams network in meters (map subset)\fR
.br
\fIEuclidean distance from the streams network in meters (detail, numbers shown
with d.rast.num)\fR
.SS Distance from sea in meters in latitude\-longitude location
.br
.nf
\fC
g.region raster=sea \-p
r.grow.distance \-m input=sea distance=dist_from_sea_geodetic metric=geodesic
r.colors map=dist_from_sea_geodetic color=rainbow
\fR
.fi
.PP
.br
\fIGeodesic distances to sea in meters\fR
.SH SEE ALSO
\fI
r.grow,
r.distance,
r.buffer,
r.cost,
r.patch
\fR
.PP
\fI
Wikipedia Entry:
Euclidean Metric
.br
Wikipedia Entry:
Manhattan Metric
\fR
.SH AUTHORS
Glynn Clements
.SH SOURCE CODE
.PP
Available at: r.grow.distance source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual