**-3**- Perform 3D transformation
**-o**- Perform orthogonal 3D transformation
**-r**- Print RMS errors
- Print RMS errors and exit without rectifying the input map
**-b**- Do not build topology
- Advantageous when handling a large number of points
**--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

**input**=*name***[required]**- Name of input vector map
- Or data source for direct OGR access
**output**=*name***[required]**- Name for output vector map
**group**=*name*- Name of input imagery group
**points**=*name*- Name of input file with control points
**rmsfile**=*name*- Name of output file with RMS errors (if omitted or '-' output to stdout
**order**=*integer*- Rectification polynomial order (1-3)
- Options:
*1-3* - Default:
*1* **separator**=*character*- Field separator for RMS report
- Special characters: pipe, comma, space, tab, newline
- Default:
*pipe*

The *-o* flag enforces orthogonal rotation (currently for 3D only)
where the axes remain orthogonal to each other, e.g. a cube with right
angles remains a cube with right angles after transformation. This is not
guaranteed even with affine (1^{st} order) 3D transformation.

Great care should be taken with the placement of Ground Control Points. For 2D transformation, the control points must not lie on a line, instead 3 of the control points must form a triangle. For 3D transformation, the control points must not lie on a plane, instead 4 of the control points must form a triangular pyramid. It is recommended to investigate RMS errors and deviations of the Ground Control Points prior to transformation.

2D Ground Control Points can be identified in
*g.gui.gcp*.

3D Ground Control Points must be provided in a text file with the
**points** option. The 3D format is equivalent to the format for 2D
ground control points with an additional third coordinate:

x y z east north height status

If no **group** is given, the rectified vector will be written to
the current mapset. If a **group** is given and a target has been
set for this group with *i.target*,
the rectified vector will be written to the target location and mapset.

The desired order of transformation (1, 2, or 3) is selected with the
**order** option.
*v.rectify* will calculate the RMSE if the **-r** flag is
given and print out statistcs in tabular format. The last row gives a
summary with the first column holding the number of active points,
followed by average deviations for each dimension and both forward and
backward transformation and finally forward and backward overall RMSE.

- x' = a1 + b1 * x + c1 * y
- y' = a2 + b2 * x + c2 * y

- x' = a1 + b1 * x + c1 * y + d1 * z
- y' = a2 + b2 * x + c2 * y + d2 * z
- z' = a3 + b3 * x + c3 * y + d3 * z

- ((n + 1) * (n + 2) / 2)

*
g.gui.gcp,
i.group,
i.rectify,
i.target,
m.transform,
r.proj,
v.proj,
v.transform,
*

*
Manage Ground Control Points
*

based on i.rectify

Available at: v.rectify source code (history)

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© 2003-2021 GRASS Development Team, GRASS GIS 7.9.dev Reference Manual