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 12:29:50 +0100 (Tue, 08 Nov 2011) $
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