NAME

       v.transform  - Performs an affine transformation (shift, scale and rotate) 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]
       [columns=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 transformations (scaling, rotation) and translation (shifting). Several
       linear transformations can be combined in a single operation. The command can  be  used  to  georeference
       unreferenced vector maps or to modify existing 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, default 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)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual