.TH v.to.rast 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.to.rast\fR\fR  \- Converts (rasterize) a vector map into a raster map.
.SH KEYWORDS
vector, conversion, raster, rasterization
.SH SYNOPSIS
\fBv.to.rast\fR
.br
\fBv.to.rast \-\-help\fR
.br
\fBv.to.rast\fR [\-\fBd\fR] \fBinput\fR=\fIname\fR  [\fBlayer\fR=\fIstring\fR]   [\fBtype\fR=\fIstring\fR[,\fIstring\fR,...]]   [\fBcats\fR=\fIrange\fR]   [\fBwhere\fR=\fIsql_query\fR]  \fBoutput\fR=\fIname\fR \fBuse\fR=\fIstring\fR  [\fBattribute_column\fR=\fIname\fR]   [\fBrgb_column\fR=\fIname\fR]   [\fBlabel_column\fR=\fIname\fR]   [\fBvalue\fR=\fIfloat\fR]   [\fBmemory\fR=\fImemory in MB\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-d\fR" 4m
.br
Create densified lines (default: thin lines)
.br
All cells touched by the line will be set, not only those on the render path
.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 vector map
.br
Or data source for direct OGR access
.IP "\fBlayer\fR=\fIstring\fR" 4m
.br
Layer number or name
.br
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
.br
Default: \fI1\fR
.IP "\fBtype\fR=\fIstring[,\fIstring\fR,...]\fR" 4m
.br
Input feature type
.br
Options: \fIpoint, line, boundary, centroid, area\fR
.br
Default: \fIpoint,line,area\fR
.IP "\fBcats\fR=\fIrange\fR" 4m
.br
Category values
.br
Example: 1,3,7\-9,13
.IP "\fBwhere\fR=\fIsql_query\fR" 4m
.br
WHERE conditions of SQL statement without \(cqwhere\(cq keyword
.br
Example: income < 1000 and population >= 10000
.IP "\fBoutput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output raster map
.IP "\fBuse\fR=\fIstring\fR \fB[required]\fR" 4m
.br
Source of raster values
.br
Options: \fIattr, cat, val, z, dir\fR
.br
\fBattr\fR: read values from attribute table
.br
\fBcat\fR: use category values
.br
\fBval\fR: use value specified by value option
.br
\fBz\fR: use z coordinate (points or contours only)
.br
\fBdir\fR: line direction in degrees CCW from east (lines only)
.IP "\fBattribute_column\fR=\fIname\fR" 4m
.br
Name of column for \(cqattr\(cq parameter (data type must be numeric)
.IP "\fBrgb_column\fR=\fIname\fR" 4m
.br
Name of color definition column (with RRR:GGG:BBB entries)
.IP "\fBlabel_column\fR=\fIname\fR" 4m
.br
Name of column used as raster category labels
.IP "\fBvalue\fR=\fIfloat\fR" 4m
.br
Raster value (for use=val)
.br
Default: \fI1\fR
.IP "\fBmemory\fR=\fImemory in MB\fR" 4m
.br
Maximum memory to be used (in MB)
.br
Cache size for raster rows
.br
Default: \fI300\fR
.SH DESCRIPTION
\fIv.to.rast\fR transforms GRASS vector map layers into GRASS raster map
layer format. Optionally, attributes can be converted to raster category
labels.
.SH NOTES
In order to avoid unexpected results, the type of vector features
should always be specified. The default is to convert all vector
features, but if only e.g. areas should be converted use
\fItype=area\fR rather than \fItype=point,line,area\fR.
.PP
\fIv.to.rast\fR will only affect data in areas lying
inside the boundaries of the current geographic region.
A grid cell belongs to the area where the grid cell center falls into.
.PP
Before running \fIv.to.rast\fR, the user should
therefore ensure that the current geographic region is
correctly set and that the region resolution is at the
desired level.
.PP
Either the \fI\fBcolumn\fR\fR parameter or the \fI\fBvalue\fR\fR
parameter must be specified.  The \fI\fBuse\fR\fR option may be
specified alone when using the \fIdir\fR option.
.PP
\fI\fBuse\fR\fR options are:
.RS 4n
.IP \(bu 4n
\fIattr\fR \- read values from attribute table (default)
.IP \(bu 4n
\fIcat\fR  \- read values from category
.IP \(bu 4n
\fIval\fR  \- use value specified by \fI\fBvalue\fR\fR option
.IP \(bu 4n
\fIz\fR    \- use z coordinate (points or contours only)
.IP \(bu 4n
\fIdir\fR  \- line direction in degrees counterclockwise from east (lines only)
.RE
.PP
The \fI\fBcolumn\fR\fR parameter uses an existing column from the vector map
database table as the category value in the output raster map. Existing table
columns can be shown by using \fIdb.describe\fR.
.PP
An empty raster map layer will be created if the vector map layer has not
been assigned category/attribute labels (e.g., through use of
v.category option=add).
.PP
Otherwise:
.RS 4n
.IP \(bu 4n
Labeled areas and/or centroids will produce filled raster coverages with edges
that straddle the original area boundary \fBas long as the boundary is NOT
labeled\fR.
.br
(Use v.category option=del type=boundary to remove.)
.IP \(bu 4n
Labeled lines and boundaries will produce lines of raster cells which touch the
original vector line. This tends to be more aggressive than area\-only conversions.
.IP \(bu 4n
Points and orphaned centroids will be converted into single cells on the
resultant raster map.
.RE
.PP
.PP
\fBLine directions\fR are given in degrees counterclockwise from east.
.PP
.PP
Raster category labels are supported for all of \fIuse=\fR except \fIuse=z\fR.
.PP
The \fB\-d\fR flag applies only to lines and boundaries, the default is
to set only those cells on the render path (thin line).
.PP
Boundaries (usually without categories) can be rasterized with
.br
.nf
\fC
v.to.rast type=boundary layer=\-1 use=val
\fR
.fi
.SH EXAMPLES
.SS Convert a vector map and use column SPEED from attribute table
.br
.nf
\fC
db.describe \-c table=vect_map
ncols:3
Column 1: CAT
Column 2: SPEED
Column 3: WIDTH
\fR
.fi
.br
.nf
\fC
v.to.rast input=vect_map output=raster_map attribute_column=SPEED type=line
\fR
.fi
.SS Calculate stream directions from a river vector map (Spearfish)
.br
.nf
\fC
v.to.rast input=streams output=streamsdir use=dir
\fR
.fi
.SS Calculate slope along path
Using slope and aspect maps, compute slope along a bus route (use full NC sample dataset):
.br
.nf
\fC
g.region raster=elevation \-p
r.slope.aspect elevation=elevation slope=slope aspect=aspect
# compute direction of the bus route
v.to.rast input=busroute11 type=line output=busroute11_dir use=dir
# extract steepest slope values and transform them into slope along path
r.mapcalc \(dqroute_slope = if(busroute11, slope)\(dq
r.mapcalc \(dqroute_slope_dir = abs(atan(tan(slope) * cos(aspect \- busroute11_dir)))\(dq
\fR
.fi
.br
Slope in degrees along bus route
.SS Convert a vector polygon map to raster including descriptive labels
In this example, the ZIP code vector map is rasterized (North Carolina
sample dataset):
.br
.nf
\fC
# rasterize ZIP codes at 50m raster resolution
g.region vector=zipcodes_wake res=50 \-ap
# vector to raster conversion, with category labels
v.to.rast input=zipcodes_wake output=myzipcodes use=attr attribute_column=\(dqZIPNUM\(dq label_column=\(dqNAME\(dq
\fR
.fi
.SS Convert vector points to raster with raster cell binning
In this example, the number of schools per raster cell are counted
(North Carolina sample dataset):
.br
.nf
\fC
g.copy vector=schools_wake,myschools_wake
# set computation region for raster binning
g.region vector=myschools_wake res=5000 \-p \-a
# add new column for counting
v.db.addcolumn myschools_wake column=\(dqvalue integer\(dq
v.db.update myschools_wake column=value value=1
# verify attributes
v.db.select myschools_wake column=cat,value
v.out.ascii input=myschools_wake output=\- column=value
# export and import on the fly, use 4th column (value) as input
v.out.ascii input=myschools_wake output=\- column=value | r.in.xyz input=\- \(rs
            z=4 output=schools_wake_aggreg method=sum
d.mon wx0
d.rast schools_wake_aggreg
d.vect schools_wake
d.grid 5000
\fR
.fi
.br
Number of schools per raster cell
.SH SEE ALSO
\fI
db.describe,
v.category
\fR
.SH AUTHORS
Original code: Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
.br
GRASS 6.0 updates: Radim Blazek, ITC\-irst, Trento, Italy
.br
Stream directions: Jaro Hofierka and Helena Mitasova
.br
GRASS 6.3 code cleanup and label support: Brad Douglas
.PP
.SH SOURCE CODE
.PP
Available at: v.to.rast source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual