Provided by: grass-doc_7.4.0-1_all

#### NAME

```       m.transform  - Computes a coordinate transformation based on the control points.

```

#### KEYWORDS

```       miscellaneous, transformation, GCP

```

#### SYNOPSIS

```       m.transform
m.transform --help
m.transform  [-srx]  group=name order=integer  [format=string[,string,...]]   [input=name]
[--help]  [--verbose]  [--quiet]  [--ui]

Flags:
-s
Display summary information

-r
Reverse transform of coords file or coeff. dump
Target east,north coordinates to local x,y

-x
Display transform matrix coefficients

--help
Print usage summary

--verbose
Verbose module output

--quiet
Quiet module output

--ui
Force launching GUI dialog

Parameters:
group=name [required]
Name of input imagery group

order=integer [required]
Rectification polynomial order
Options: 1-3
Default: 1

format=string[,string,...]
Output format
Options: idx, src, dst, fwd, rev, fxy, rxy, fd, rd
Default: fd,rd
idx: point index
src: source coordinates
dst: destination coordinates
fwd: forward coordinates (destination)
rev: reverse coordinates (source)
fxy: forward coordinates difference (destination)
rxy: reverse coordinates difference (source)
fd: forward error (destination)
rd: reverse error (source)

input=name
File containing coordinates to transform ("-" to read from stdin)
Local x,y coordinates to target east,north

```

#### DESCRIPTION

```       m.transform is an utility to compute transformation  based  upon  GCPs  and  output  error
measurements.

```

#### NOTES

```       For coordinates given with the input file option or fed from stdin, the input format is "x
y" with one coordinate pair per line.

The transformations are:

order=1:
e = [E0 E1][1].[1]
[E2  0][e] [n]
n = [N0 N1][1].[1]
[N2  0][e] [n]
order=2:
e = [E0 E1 E3][1 ] [1 ]
[E2 E4  0][e ].[n ]
[E5  0  0][e²] [n²]
n = [N0 N1 N3][1 ] [1 ]
[N2 N4  0][e ].[n ]
[N5  0  0][e²] [n²]
order=3:
e = [E0 E1 E3 E6][1 ] [1 ]
[E2 E4 E7  0][e ].[n ]
[E5 E8  0  0][e²] [n²]
[E9  0  0  0][e³] [n³]
n = [N0 N1 N3 N6][1 ] [1 ]
[N2 N4 N7  0][e ].[n ]
[N5 N8  0  0][e²] [n²]
[N9  0  0  0][e³] [n³]
["." = dot-product, (AE).N = N’EA.]

In other words, order=1 and order=2 are equivalent to order=3 with the higher coefficients
equal to zero.

```

#### SEEALSO

```        i.rectify, v.rectify, v.transform

```

#### AUTHORS

```       Brian J. Buckley
Glynn Clements
Hamish Bowman

Last changed: \$Date: 2014-11-28 16:43:22 +0100 (Fri, 28 Nov 2014) \$

```

#### SOURCECODE

```       Available at: m.transform source code (history)

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© 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual
```