NAME

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

KEYWORDS

       general, transformation, GCP

SYNOPSIS

       g.transform
       g.transform help
       g.transform  [-srx] group=name order=integer  [format=string[,string,...]]   [coords=name]
       [--verbose]  [--quiet]

   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

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       group=name
           Name of input imagery group

       order=integer
           Rectification polynomial order
           Options: 1-3

       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)

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

DESCRIPTION

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

NOTES

       For  coordinates  given with the coords 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.

SEE ALSO

       i.rectify

AUTHORS

       Brian J. Buckley
       Glynn Clements
       Hamish Bowman

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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