# Convert coordinates
**URL:** https://discourse.itk.org/t/convert-coordinates/1402
**Category:** Beginner Questions
**Created:** [November 7, 2018, 5:57pm UTC](https://discourse.itk.org/t/convert-coordinates/1402 "2018-11-07T17:57:17Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@kjwjj627](https://discourse.itk.org/u/kjwjj627)
#### Post date: [November 7, 2018, 5:57pm UTC](https://discourse.itk.org/t/convert-coordinates/1402/1 "2018-11-07T17:57:17Z")
Hello all!
I am a beginner to learn ITK.
I want to know how do I convert image coordinates into world coordinates. For example, I have a coordinate, (-57.81263, -0.0006029, -529.4), and I want to express this coordinate in image into coordinate in world.
Thank you for your any help.
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### Author:  [@matt.mccormick](https://discourse.itk.org/u/matt.mccormick)
#### Post date: [November 7, 2018, 6:48pm UTC](https://discourse.itk.org/t/convert-coordinates/1402/2 "2018-11-07T18:48:13Z")
Welcome to ITK!
Great question.
As explained in [The ITK Software Guide](https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch4.html#x45-500004.1),
> For a given index I3X1, the physical location P3X1 is calculated as following:
>
> (4.1)
>
> where D is an orthonormal direction cosines matrix and S is the image spacing diagonal matrix.)
See also,
> Figure 4.1: Geometrical concepts associated with the ITK image.
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### Author:  [@matt.mccormick](https://discourse.itk.org/u/matt.mccormick)
#### Post date: [November 7, 2018, 6:59pm UTC](https://discourse.itk.org/t/convert-coordinates/1402/3 "2018-11-07T18:59:22Z")
Also, the function to call is `TransformContinuousIndexToPhysicalPoint` on an `itk::Image`.