# Unit of Vectors in a Deformation/displacement Vector Field

**URL:** https://discourse.itk.org/t/unit-of-vectors-in-a-deformation-displacement-vector-field/6101
**Category:** Beginner Questions
**Tags:** registration, python, dicom
**Created:** [July 27, 2023, 1:04pm UTC](https://discourse.itk.org/t/unit-of-vectors-in-a-deformation-displacement-vector-field/6101 "2023-07-27T13:04:08Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![RT\_newbie](https://discourse.itk.org/letter_avatar_proxy/v4/letter/r/f17d59/32.png) [@RT\_newbie](https://discourse.itk.org/u/RT_newbie)
#### Post date: [July 27, 2023, 1:04pm UTC](https://discourse.itk.org/t/unit-of-vectors-in-a-deformation-displacement-vector-field/6101/1 "2023-07-27T13:04:08Z")

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Hi  
I have a basic question that I cannot wrap my head around because I might have thought about a problem to solve for too long.

When I non-rigidly register two images and look at the deformation field array, are the vectors image(index) or physical(cm/mm) magnitudes/directions?

Thank you for your help!

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### Author: ![zivy](https://discourse.itk.org/user_avatar/discourse.itk.org/zivy/32/1726_2.png) [@zivy](https://discourse.itk.org/u/zivy)
#### Post date: [July 27, 2023, 3:05pm UTC](https://discourse.itk.org/t/unit-of-vectors-in-a-deformation-displacement-vector-field/6101/2 "2023-07-27T15:05:01Z")

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Hello @RT_newbie,

All transformations in ITK/SimpleITK are in physical space, so cm/mm/nm…

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<div class="post-metadata">

### Author: ![RT\_newbie](https://discourse.itk.org/letter_avatar_proxy/v4/letter/r/f17d59/32.png) [@RT\_newbie](https://discourse.itk.org/u/RT_newbie)
#### Post date: [August 1, 2023, 8:05am UTC](https://discourse.itk.org/t/unit-of-vectors-in-a-deformation-displacement-vector-field/6101/3 "2023-08-01T08:05:42Z")

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Thanks a lot!