Hi! You can try to use the new low level api to get head coordinates in mm.
https://www.nuget.org/packages/Tobii.StreamEngine.Native/
https://www.nuget.org/packages/Tobii.StreamEngine/
This is a low level API so please only use it if you know why you are doing it. Very little support is going to be provided.
It’s worth noting that position signal (especially Z coordinate) is not very precise, but may be suitable for some use cases.