Provided by: grass-doc_6.4.3-3_all bug


       v.transform   -  Performs  an  affine transformation (shift, scale and rotate, or GPCs) on
       vector map.


       vector, transformation


       v.transform help
       v.transform   [-qtms]   input=name    [layer=integer]    output=name     [pointsfile=name]
       [xshift=float]     [yshift=float]     [zshift=float]     [xscale=float]     [yscale=float]
       [zscale=float]     [zrot=float]      [table=name]      [columns=string]      [--overwrite]
       [--verbose]  [--quiet]

           Suppress display of residuals or other information

           Shift all z values to bottom=0

           Print the transformation matrix to stdout

           Instead  of  points  use  transformation  parameters  (xshift, yshift, zshift, xscale,
           yscale, zscale, zrot)

           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Name of input vector map

           Layer number
           A single vector map  can  be  connected  to  multiple  database  tables.  This  number
           determines which table to use.
           Default: -1

           Name for output vector map

           ASCII file holding transform coordinates
           If  not  given,  transformation  parameters  (xshift,  yshift, zshift, xscale, yscale,
           zscale, zrot) are used instead

           Shifting value for x coordinates
           Default: 0.0

           Shifting value for y coordinates
           Default: 0.0

           Shifting value for z coordinates
           Default: 0.0

           Scaling factor for x coordinates
           Default: 1.0

           Scaling factor for y coordinates
           Default: 1.0

           Scaling factor for z coordinates
           Default: 1.0

           Rotation around z axis in degrees counterclockwise
           Default: 0.0

           Name of table containing transformation parameters

           Name of attribute column(s) used as transformation parameters
           Format: parameter:column, e.g. xshift:xs,yshift:ys,zrot:zr


       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.


       When using an ASCII table containing source and target coordinate pairs, in each row  four
       coordinate  values  separated by white space have to be specified.  Comments are permitted
       and have to be indicated by a '#' character.

       Example for a points file of a linear transformation from XY to UTM coordinates (L:  left,
       R: right, U: upper, L: lower, N, S, W, E):
       # Linear transformation from XY to UTM coordinates:
       # 4 maps corners defined
       # UL NW
       # UR NE
       # LR SW
       # LL SE
       -584  585  598000 4920770
        580  585  598020 4920770
        580 -600  598020 4920750
       -584 -600  598000 4920750

       The  ground control points may be also (ir)regularly distributed and can be more than four

       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.

   Affine Transformation Matrix
       The  affine  transfomation matrix can optionally be printed with the '-m' flag. The format
       of the matrix is:
       | x_offset a b |
       | y_offset d e |
        This format can be used in the Affine() function of PostGIS [Affine(geom,  a,  b,  d,  e,
       xoff, yoff)], or directly compared to the output of a similar operation performed in R.


   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' with a 4 point transformation.
       v.transform -t in=watertowerXY out=watertowerUTM points=wt.points zscale=0.04 zshift=1320

   Extrude 2D vector points to 3D based on attribute column values
       Spearfish example with manual table editing for vertical shift:
       # create table containing transformation parameters:
       echo "create table archsites_t (cat int, zs double)" | db.execute
       # insert transformation parameters for category 1:
       echo "insert into archsites_t values (1, 1000)" | db.execute
       # insert transformation parameters for category 2 (and so forth):
       echo "insert into archsites_t values (2, 2000)" | db.execute
       # 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.addcol myarchsites col="zs double precision"
       # set region to elevation map and fetch individual heights:
       g.region rast=elevation.10m -p
       v.what.rast myarchsites rast=elevation.10m col=zs
       # verify: myarchsites
       # perform transformation to 3D
       v.transform -t myarchsites output=myarchsites3d column="zshift:zs" table=myarchsites
       # drop table containing transformation parameters
       v.db.dropcol myarchsites3d col=zs
        The resulting map is a 3D vector map.



       Radim Blazek, ITC-irst, Trento, Italy,
       Column support  added  by  Martin  Landa,  FBK-irst  (formerly  ITC-irst),  Trento,  Italy

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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