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) $ Full index © 2003-2014 GRASS Development Team