---
name: "i.ortho.transform"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/i.ortho.transform"
---

# i.ortho.transform(1grass)

Computes a coordinate transformation based on the control points.

## 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** \[-**srxp**\] **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

- **-p**

  Enable panorama camera correction

- **--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.

If coordinates are given with the **input** file option or fed from `stdin`, both the input and the output format is "x y z" with one coordinate pair per line. Reverse transform is performed with the **-r** flag.

The **format** option determines how control points are printed out. A summary on the control points can be printed with the **-s** flag. The summary includes maximum deviation observed when transforming GCPs and overall RMS. The **format** option is ignored when coordinates are given with the **input** file option.

## NOTES

Ortho-transformation is a 2-step transformation. First, source coordinates are transformed to sensor coordinates, then sensor coordinates are transformed to target coordinates.

## SEE ALSO

*i.rectify*

## TODO

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

## AUTHORS

Brian J. Buckley\
 Glynn Clements\
 Hamish Bowman

## SOURCE CODE

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

Accessed: Monday Feb 24 17:51:39 2025

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