GRASS GIS: v.to.rast

NAME

v.to.rast - Converts a binary GRASS vector map layer into a GRASS raster map layer.

KEYWORDS

vector, raster, conversion

SYNOPSIS

v.to.rast
v.to.rast help
v.to.rast input=name output=name [use=string] [type=string[,string,...]] [layer=integer] [column=name] [value=float] [rows=integer] [rgbcolumn=name] [labelcolumn=name] [--overwrite] [--verbose] [--quiet]

Flags:

--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name: Name of input vector map
output=name: Name for output raster map
use=string: Source of raster values; Options: attr,cat,val,z,dir; Default: attr; 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)
type=string[,string,...]: Type; Feature type(s); Options: point,line,area; Default: point,line,area
layer=integer: Layer number; A single vector map can be connected to multiple database tables. This number determines which table to use.; Default: 1
column=name: Name of column for attr parameter (data type must be numeric)
value=float: Raster value; Default: 1
rows=integer: Number of rows to hold in memory; Default: 4096
rgbcolumn=name: Name of color definition column (with RRR:GGG:BBB entries)
labelcolumn=name: Name of column used as raster category labels

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: 2008-02-19 12:12:24 -0800 (Tue, 19 Feb 2008) $

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