GRASS GIS manual: v.to.rast

NAME

v.to.rast - Converts (rasterize) a vector map into a raster map.

KEYWORDS

vector, conversion, raster, rasterization

SYNOPSIS

v.to.rast

v.to.rast --help

v.to.rast [-d] input=name [layer=string] [type=string[,string,...]] [cats=range] [where=sql_query] output=name use=string [attribute_column=name] [rgb_column=name] [label_column=name] [value=float] [memory=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-d: Create densified lines (default: thin lines); All cells touched by the line will be set, not only those on the render path
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name [required]: Name of input vector map; Or data source for direct OGR access
layer=string: Layer number or name; 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.; Default: 1
type=string[,string,...]: Input feature type; Options: point, line, area; Default: point,line,area
cats=range: Category values; Example: 1,3,7-9,13
where=sql_query: WHERE conditions of SQL statement without 'where' keyword; Example: income < 1000 and inhab >= 10000
output=name [required]: Name for output raster map
use=string [required]: Source of raster values; Options: attr, cat, val, z, dir; attr: read values from attribute table; cat: use category values; val: use value specified by value option; z: use z coordinate (points or contours only); dir: output as flow direction (lines only)
attribute_column=name: Name of column for 'attr' parameter (data type must be numeric)
rgb_column=name: Name of color definition column (with RRR:GGG:BBB entries)
label_column=name: Name of column used as raster category labels
value=float: Raster value (for use=val); Default: 1
memory=integer: Maximum memory to be used (in MB); Cache size for raster rows; Default: 300

DESCRIPTION
NOTES
EXAMPLES
SEE ALSO
AUTHORS

DESCRIPTION

v.to.rast transforms GRASS vector map layers into GRASS raster map layer format. Optionally, attributes can be converted into raster category labels.

NOTES

v.to.rast will only affect data in areas lying inside the boundaries of the current geographic region. Before running v.to.rast, the user should therefore ensure that the current geographic region is correctly set and that the region resolution is at the desired level.

Either the column parameter or the value parameter must be specified. The use option may be specified alone when using the dir option.

use options are:

attr - read values from attribute table (default)
cat - read values from category
val - use value specified by value option
z - use z coordinate (points or contours only)
dir - output as flow direction in degrees (lines only)

The column 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 db.describe.

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).

Otherwise:

Labeled areas and/or centroids will produce filled raster coverages with edges that straddle the original area boundary as long as the boundary is NOT labeled.
(Use v.category option=del type=boundary to remove.)
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.
Points and orphaned centroids will be converted into single cells on the resultant raster map.

Flow directions are given in degrees counterclockwise from east.

Raster category labels are supported for all of use= except use=z.

EXAMPLES

1. Convert a vector map and use column SPEED from attribute table

db.describe -c table=vect_map

ncols:3
Column 1: CAT
Column 2: SPEED
Column 3: WIDTH

v.to.rast in=vect_map out=raster_map col=SPEED

2. Calculate stream directions from a river vector map (Spearfish)

v.to.rast in=streams out=streamsdir use=dir

3. Convert a vector polygon map to raster including descriptive labels (Spearfish)

v.to.rast in=fields out=myfields use=attr col=cat labelcol=label
r.category myfields

AUTHORS

Original code: Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
GRASS 6.0 updates: Radim Blazek, ITC-irst, Trento, Italy
Stream directions: Jaro Hofierka and Helena Mitasova
GRASS 6.3 code cleanup and label support: Brad Douglas

Last changed: $Date: 2011-11-08 13:24:20 -0800 (Tue, 08 Nov 2011) $

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