GRASS GIS manual: m.transform

Note: A new GRASS GIS stable version has been released: GRASS GIS 7.8, available here.
Updated manual page: here

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
NOTES
SEE ALSO
AUTHORS

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.

AUTHORS

Brian J. Buckley
Glynn Clements
Hamish Bowman

Last changed: $Date$

SOURCE CODE

Available at: m.transform source code (history)