# Mapping between different coordinate systems
**URL:** https://discourse.vtk.org/t/mapping-between-different-coordinate-systems/11095
**Category:** Web
**Created:** [March 30, 2023, 9:13am UTC](https://discourse.vtk.org/t/mapping-between-different-coordinate-systems/11095 "2023-03-30T09:13:42Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Lukasz\_Skrzeszewski](https://discourse.vtk.org/u/Lukasz_Skrzeszewski)
#### Post date: [March 30, 2023, 9:13am UTC](https://discourse.vtk.org/t/mapping-between-different-coordinate-systems/11095/1 "2023-03-30T09:13:42Z")
I am trying to hook up to interactor, instance of `vtkRenderWindowInteractor`, callbacks `onMouseMove`, `onMouseWheel` and so on.
I have noticed that the position returned in the event is in a different coordinate system than I have expected. Basically (0,0) is in the bottom-left corner and the width and height are not in pixel space.
I would like to be able to convert the position returned by the event to “standard” canvas coordinates with (0,0) being in the top-left.
Can someone point me in to the right direction? I have been going through the docs for `vtkCoordinate` and `vtkPixelSpaceCallbackMapper` but I dont seem to find what I am looking for.
Additionally I would appreciate if you can point me to some docs/tutorials where I can learn more about vtk.js different coordinate systems and how things work.
Cheers.
---
### Author:  [@Sebastien\_Jourdain](https://discourse.vtk.org/u/Sebastien_Jourdain)
#### Post date: [March 31, 2023, 2:06pm UTC](https://discourse.vtk.org/t/mapping-between-different-coordinate-systems/11095/2 "2023-03-31T14:06:51Z")
The x,y you are getting use the VTK coordinate system. You can just flip Y using the height of the VTK render window assuming you don’t have any devicePixelRatio scaling.
---
### Author:  [@Lukasz\_Skrzeszewski](https://discourse.vtk.org/u/Lukasz_Skrzeszewski)
#### Post date: [March 31, 2023, 2:38pm UTC](https://discourse.vtk.org/t/mapping-between-different-coordinate-systems/11095/3 "2023-03-31T14:38:32Z")
Perfect! I think that must be it, the `devicePixelRatio`. I didn’t think about it. Thank you.