v.transform(1grass) GRASS GIS User's Manual v.transform(1grass)
NAME
v.transform - Performs an affine transformation (shift, scale and ro-
tate) on vector map.
KEYWORDS
vector, transformation, geometry, GCP
SYNOPSIS
v.transform
v.transform --help
v.transform [-twxyab] input=name [layer=string] output=name
[xshift=float] [yshift=float] [zshift=float] [xscale=float]
[yscale=float] [zscale=float] [zrotation=float] [col-
umns=name[,name,...]] [--overwrite] [--help] [--verbose] [--quiet]
[--ui]
Flags:
-t
Shift all z values to bottom=0
-w
Swap coordinates x, y and then apply other parameters
-x
Swap coordinates x, z and then apply other parameters
-y
Swap coordinates y, z and then apply other parameters
-a
Swap coordinates after the other transformations
-b
Do not build topology
--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 (’-1’ for all layers)
A single vector map can be connected to multiple database tables.
This number determines which table to use. When used with direct
OGR access this is the layer name.
Default: -1
output=name [required]
Name for output vector map
xshift=float
Shifting value for x coordinates
Default: 0.0
yshift=float
Shifting value for y coordinates
Default: 0.0
zshift=float
Shifting value for z coordinates
Default: 0.0
xscale=float
Scaling factor for x coordinates
Default: 1.0
yscale=float
Scaling factor for y coordinates
Default: 1.0
zscale=float
Scaling factor for z coordinates
Default: 1.0
zrotation=float
Rotation around z axis in degrees (counter-clockwise)
Default: 0.0
columns=name[,name,...]
Name of attribute column(s) used as transformation parameters
Format: parameter:column, e.g. xshift:xs,yshift:ys,zrot:zr
DESCRIPTION
v.transform performs an affine transformation (translate and rotate) of
a vector map. An affine transform includes one or several linear trans-
formations (scaling, rotation) and translation (shifting). Several lin-
ear transformations can be combined in a single operation. The command
can be used to georeference unreferenced vector maps or to modify ex-
isting geocoded maps.
NOTES
Coordinate transformation based on Ground Control Points (GCPs) is done
by v.rectify and not supported by v.transform.
Transformation parameters (i.e. xshift, yshift, etc.) can be fetched
from attribute table connected to the vector map. In this case vector
objects can be transformed with different parameters based on their
category number. If the parameter cannot be fetched from the table, de-
fault value is used instead.
Note that the transformation matrix can be printed by m.transform.
EXAMPLE
DXF/DWG drawings
Most DXF/DWG drawings are done within XY coordinate space. To transform
them to a national grid, we can use v.transform together with v.rectify
and a first-order transformation.
v.transform -t in=watertowerXY out=watertower_z zscale=0.04 zshift=1320
v.rectify in=watertower_z out=watertowerUTM points=wt.points order=1
Extrude 2D vector points to 3D based on attribute column values
Spearfish example with manual table editing for vertical shift:
# work on own map copy:
g.copy vect=archsites@PERMANENT,myarchsites
# add new ’zs’ column to later store height of each site:
v.db.addcolumn myarchsites col="zs double precision"
v.db.update myarchsites layer=1 column=zs value="cat * 1000"
# perform z transformation:
v.transform -t input=archsites output=myarchsites3d column="zshift:zs" table="archsites_t"
# drop table containing transformation parameters:
echo "drop table archsites_t" | db.execute
The resulting map is a 3D vector map.
Extrude 2D vector points to 3D based on attribute column values
Spearfish example with automated elevation extraction for vertical
shift:
# work on own map copy:
g.copy vect=archsites@PERMANENT,myarchsites
# add new ’zs’ column to later store height of each site:
v.db.addcolumn myarchsites col="zs double precision"
# set region to elevation map and fetch individual heights:
g.region raster=elevation.10m -p
v.what.rast myarchsites rast=elevation.10m col=zs
# verify:
v.db.select myarchsites
# perform transformation to 3D
v.transform -t myarchsites output=myarchsites3d column="zshift:zs" layer=1
# drop table containing transformation parameters
v.db.dropcolumn myarchsites3d col=zs
The resulting map is a 3D vector map.
SEE ALSO
m.transform, i.rectify, v.rectify, r.region
AUTHOR
Radim Blazek, ITC-irst, Trento, Italy,
Column support added by Martin Landa, FBK-irst (formerly ITC-irst),
Trento, Italy (2007/09)
SOURCE CODE
Available at: v.transform source code (history)
Accessed: unknown
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GRASS 7.8.7 v.transform(1grass)
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