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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.

       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.

NOTES

       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.

SEE ALSO

        i.rectify, v.rectify, v.transform

AUTHORS

       Brian J. Buckley
       Glynn Clements
       Hamish Bowman

       Last changed: $Date: 2018-03-14 11:57:02 +0100 (Wed, 14 Mar 2018) $

SOURCE CODE

       Available at: m.transform source code (history)

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