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

AUTHORS

       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: Thursday Aug 01 11:31:19 2024

       Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual