# How does the Landmark registration get the "from" position

**URL:** https://discourse.slicer.org/t/how-does-the-landmark-registration-get-the-from-position/25036
**Category:** Support
**Tags:** registration
**Created:** [September 1, 2022, 3:39am UTC](https://discourse.slicer.org/t/how-does-the-landmark-registration-get-the-from-position/25036 "2022-09-01T03:39:22Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![whu](https://avatars.discourse-cdn.com/v4/letter/w/7ab992/32.png) [@whu](https://discourse.slicer.org/u/whu)
#### Post date: [September 1, 2022, 3:39am UTC](https://discourse.slicer.org/t/how-does-the-landmark-registration-get-the-from-position/25036/1 "2022-09-01T03:39:22Z")

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Hi,  
In order to make a realtime EM tracker on the physical model, and the needle followed in the virtual model, I tried the Landmark registration tutorial in IGT.  
Firstly, using the vtkLandmarkTransform, I can get the expected transform positions.  
But when using the Fiducial Registration Wizard, I don’t know how does the module get the “from” markup points position from a video ? The “to” positions are easy from slicer.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/2/2/223e3d49f1096e416759e0090485bc63ee8a316c.png)  
The EM tracker is connected using Plus, the realtime transforms can be seen in the transform module.  
so, maybe this is near to the truth. 🙏  
thanks.