m.transform.1grass man page

m.transform — 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


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.


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:


    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

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

Source Code

Available at: m.transform source code (history)

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

© 2003-2017 GRASS Development Team, GRASS GIS 7.2.1 Reference Manual


GRASS 7.2.1 Grass User's Manual