.TH g.transform 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBg.transform\fR\fR  - Computes a coordinate transformation based on the control points.
.SH KEYWORDS
general, transformation, GCP
.SH SYNOPSIS
\fBg.transform\fR
.br
\fBg.transform help\fR
.br
\fBg.transform\fR [\-\fBsrx\fR] \fBgroup\fR=\fIname\fR \fBorder\fR=\fIinteger\fR  [\fBformat\fR=\fIstring\fR[,\fIstring\fR,...]]   [\fBcoords\fR=\fIname\fR]   [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-s\fR" 4m
.br
Display summary information
.IP "\fB\-r\fR" 4m
.br
Reverse transform of coords file or coeff. dump
.br
Target east,north coordinates to local x,y
.IP "\fB\-x\fR" 4m
.br
Display transform matrix coefficients
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBgroup\fR=\fIname\fR" 4m
.br
Name of input imagery group
.IP "\fBorder\fR=\fIinteger\fR" 4m
.br
Rectification polynomial order
.br
Options: \fI1-3\fR
.IP "\fBformat\fR=\fIstring[,\fIstring\fR,...]\fR" 4m
.br
Output format
.br
Options: \fIidx,src,dst,fwd,rev,fxy,rxy,fd,rd\fR
.br
Default: \fIfd,rd\fR
.br
\fBidx\fR: point index
.br
\fBsrc\fR: source coordinates
.br
\fBdst\fR: destination coordinates
.br
\fBfwd\fR: forward coordinates (destination)
.br
\fBrev\fR: reverse coordinates (source)
.br
\fBfxy\fR: forward coordinates difference (destination)
.br
\fBrxy\fR: reverse coordinates difference (source)
.br
\fBfd\fR: forward error (destination)
.br
\fBrd\fR: reverse error (source)
.IP "\fBcoords\fR=\fIname\fR" 4m
.br
File containing coordinates to transform ("-" to read from stdin)
.br
Local x,y coordinates to target east,north
.PP
.SH DESCRIPTION
\fIg.transform\fR is an utility to compute transformation
based upon GCPs and output error measurements.
.SH NOTES
For coordinates given with the \fBcoords\fR file option or fed from
stdin, the input format is "x y" with one coordinate pair per
line.
.PP
The transformations are:
.PP
order=1:
\fC
.DS
.br
    e = [E0 E1][1].[1]
.br
        [E2  0][e] [n]
.br
   
.br
    n = [N0 N1][1].[1]
.br
        [N2  0][e] [n]
.br
.DE
\fR
order=2:
\fC
.DS
.br
.br
    e = [E0 E1 E3][1 ] [1 ]
.br
        [E2 E4  0][e ].[n ]
.br
        [E5  0  0][e²] [n²]
.br
   
.br
    n = [N0 N1 N3][1 ] [1 ]
.br
        [N2 N4  0][e ].[n ]
.br
        [N5  0  0][e²] [n²]
.br
.DE
\fR
order=3:
\fC
.DS
.br
.br
    e = [E0 E1 E3 E6][1 ] [1 ]
.br
        [E2 E4 E7  0][e ].[n ]
.br
        [E5 E8  0  0][e²] [n²]
.br
        [E9  0  0  0][e³] [n³]
.br
   
.br
    n = [N0 N1 N3 N6][1 ] [1 ]
.br
        [N2 N4 N7  0][e ].[n ]
.br
        [N5 N8  0  0][e²] [n²]
.br
        [N9  0  0  0][e³] [n³]
.br
.DE
\fR
["." = dot-product, (AE).N = N'EA.]
.PP
In other words, order=1 and order=2 are equivalent to order=3 with
the higher coefficients equal to zero.
.SH SEE ALSO
\fIi.rectify\fR
.SH AUTHORS
Brian J. Buckley
.br
Glynn Clements
.br
Hamish Bowman
.PP
\fILast changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $\fR
.PP
Full index
.PP
© 2003-2014 GRASS Development Team