1v.transform(1)              GRASS GIS User's Manual             v.transform(1)
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4

NAME

6       v.transform   - Performs an affine transformation (shift, scale and ro‐
7       tate) on vector map.
8

KEYWORDS

10       vector, transformation, geometry, GCP
11

SYNOPSIS

13       v.transform
14       v.transform --help
15       v.transform   [-twxyab]   input=name     [layer=string]     output=name
16       [xshift=float]     [yshift=float]     [zshift=float]     [xscale=float]
17       [yscale=float]       [zscale=float]       [zrotation=float]       [col‐
18       umns=name[,name,...]]   [--overwrite]  [--help]  [--verbose]  [--quiet]
19       [--ui]
20
21   Flags:
22       -t
23           Shift all z values to bottom=0
24
25       -w
26           Swap coordinates x, y and then apply other parameters
27
28       -x
29           Swap coordinates x, z and then apply other parameters
30
31       -y
32           Swap coordinates y, z and then apply other parameters
33
34       -a
35           Swap coordinates after the other transformations
36
37       -b
38           Do not build topology
39
40       --overwrite
41           Allow output files to overwrite existing files
42
43       --help
44           Print usage summary
45
46       --verbose
47           Verbose module output
48
49       --quiet
50           Quiet module output
51
52       --ui
53           Force launching GUI dialog
54
55   Parameters:
56       input=name [required]
57           Name of input vector map
58           Or data source for direct OGR access
59
60       layer=string
61           Layer number or name (’-1’ for all layers)
62           A single vector map can be connected to multiple  database  tables.
63           This  number  determines  which table to use. When used with direct
64           OGR access this is the layer name.
65           Default: -1
66
67       output=name [required]
68           Name for output vector map
69
70       xshift=float
71           Shifting value for x coordinates
72           Default: 0.0
73
74       yshift=float
75           Shifting value for y coordinates
76           Default: 0.0
77
78       zshift=float
79           Shifting value for z coordinates
80           Default: 0.0
81
82       xscale=float
83           Scaling factor for x coordinates
84           Default: 1.0
85
86       yscale=float
87           Scaling factor for y coordinates
88           Default: 1.0
89
90       zscale=float
91           Scaling factor for z coordinates
92           Default: 1.0
93
94       zrotation=float
95           Rotation around z axis in degrees (counter-clockwise)
96           Default: 0.0
97
98       columns=name[,name,...]
99           Name of attribute column(s) used as transformation parameters
100           Format: parameter:column, e.g. xshift:xs,yshift:ys,zrot:zr
101

DESCRIPTION

103       v.transform performs an affine transformation (translate and rotate) of
104       a vector map. An affine transform includes one or several linear trans‐
105       formations (scaling, rotation) and translation (shifting). Several lin‐
106       ear  transformations can be combined in a single operation. The command
107       can be used to georeference unreferenced vector maps or to  modify  ex‐
108       isting geocoded maps.
109

NOTES

111       Coordinate transformation based on Ground Control Points (GCPs) is done
112       by v.rectify and not supported by v.transform.
113
114       Transformation parameters (i.e. xshift, yshift, etc.)  can  be  fetched
115       from  attribute  table connected to the vector map. In this case vector
116       objects can be transformed with different  parameters  based  on  their
117       category number. If the parameter cannot be fetched from the table, de‐
118       fault value is used instead.
119
120       Note that the transformation matrix can be printed by m.transform.
121

EXAMPLE

123   DXF/DWG drawings
124       Most DXF/DWG drawings are done within XY coordinate space. To transform
125       them to a national grid, we can use v.transform together with v.rectify
126       and a first-order transformation.
127       v.transform -t in=watertowerXY out=watertower_z zscale=0.04 zshift=1320
128       v.rectify in=watertower_z out=watertowerUTM points=wt.points order=1
129
130   Extrude 2D vector points to 3D based on attribute column values
131       Spearfish example with manual table editing for vertical shift:
132       # work on own map copy:
133       g.copy vect=archsites@PERMANENT,myarchsites
134       # add new ’zs’ column to later store height of each site:
135       v.db.addcolumn myarchsites col="zs double precision"
136       v.db.update myarchsites layer=1 column=zs value="cat * 1000"
137       # perform z transformation:
138       v.transform -t input=archsites output=myarchsites3d column="zshift:zs" table="archsites_t"
139       # drop table containing transformation parameters:
140       echo "drop table archsites_t" | db.execute
141       The resulting map is a 3D vector map.
142
143   Extrude 2D vector points to 3D based on attribute column values
144       Spearfish example with  automated  elevation  extraction  for  vertical
145       shift:
146       # work on own map copy:
147       g.copy vect=archsites@PERMANENT,myarchsites
148       # add new ’zs’ column to later store height of each site:
149       v.db.addcolumn myarchsites col="zs double precision"
150       # set region to elevation map and fetch individual heights:
151       g.region raster=elevation.10m -p
152       v.what.rast myarchsites rast=elevation.10m col=zs
153       # verify:
154       v.db.select myarchsites
155       # perform transformation to 3D
156       v.transform -t myarchsites output=myarchsites3d column="zshift:zs" layer=1
157       # drop table containing transformation parameters
158       v.db.dropcolumn myarchsites3d col=zs
159       The resulting map is a 3D vector map.
160

SEE ALSO

162        m.transform, i.rectify, v.rectify, r.region
163

AUTHORS

165       Radim Blazek, ITC-irst, Trento, Italy,
166       Column  support  added  by  Martin Landa, FBK-irst (formerly ITC-irst),
167       Trento, Italy (2007/09)
168

SOURCE CODE

170       Available at: v.transform source code (history)
171
172       Accessed: Saturday Jan 21 21:16:21 2023
173
174       Main index | Vector index | Topics index | Keywords index  |  Graphical
175       index | Full index
176
177       © 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
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181GRASS 8.2.1                                                     v.transform(1)
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