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.
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
# 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
# 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
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