Your company here — click to reach over 10,000 unique daily visitors

m.transform.1grass - Man Page

Computes a coordinate transformation based on the control points.


miscellaneous, transformation, GCP


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



Display summary information


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


Display transform matrix coefficients


Print usage summary


Verbose module output


Quiet module output


Force launching GUI dialog


group=name [required]

Name of input imagery group

order=integer [required]

Rectification polynomial order
Options: 1-3
Default: 1


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)


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


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

If coordinates are given with the input file option or fed from stdin, both the input and the output format is "x y" with one coordinate pair per line. Reverse transform is performed with the -r flag.

The format option determines how control points are printed out. A summary on the control points can be printed with the -s flag. The summary includes maximum deviation observed when transforming GCPs and overall RMS. The format option is ignored when coordinates are given with the input file option.


The transformations are:


    e = [E0 E1][1].[1]
        [E2  0][e] [n]
    n = [N0 N1][1].[1]
        [N2  0][e] [n]


    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]


    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.

See Also

i.rectify, v.rectify, v.transform


Brian J. Buckley
Glynn Clements
Hamish Bowman

Source Code

Available at: m.transform source code (history)

Accessed: Tuesday May 14 13:41:36 2024

Main index | Miscellaneous index | Topics index | Keywords index | Graphical index | Full index

© 2003-2024 GRASS Development Team, GRASS GIS 8.3.2 Reference Manual


GRASS 8.3.2 GRASS GIS User's Manual