GRASS GIS manual: i.ortho.transform

## NAME

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

## KEYWORDS

imagery, orthorectify, transformation, GCP

## SYNOPSIS

i.ortho.transform
i.ortho.transform --help
i.ortho.transform [-srx] group=name [format=string[,string,...]] [coords=name] [--help] [--verbose] [--quiet] [--ui]

### Flags:

-s
  Display summary information
-r
  Reverse transform of coords file or coeff. dump
  Target east,north,height coordinates to local x,y,z
-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
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,z coordinates to target east,north,height

## DESCRIPTION

i.ortho.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 z" 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

## TODO

Update this document with x,y,z<->E,N,H information

## AUTHORS

Brian J. Buckley
Glynn Clements
Hamish Bowman

Last changed: $Date: 2017-04-07 18:41:10 +0200 (Fri, 07 Apr 2017) $

## SOURCE CODE

Available at: i.ortho.transform source code (history)

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