Hello there,

I ran into a problem after using our original .pos files for the conversion from hitachi to .nirs
When we open the converted data in Homer3, it changes the .nirs to .snirf and displays the probe array. But the view is off and the channels don't seem to correspond to the optodes anymore. If we ran the script with the provided default 3x5.pos file, no such problem occurs.
I'm not sure, what we can do about that. The only difference between original and default file we found is the version: default=2.0, ours=2.2
We checked the .pos file for plausibility using AtlasViewer and the positioning makes sense and fits our setup.
We hope that you can give us a hint or advice in how to go from here?

Greetings,
Alex
P.S: You can find a picture comparing both approaches in the attachement

Hello Alex and thank you for your question. The pos files I created were purely to easily visualise the data in Homer2 and did not have any physiological meaning. Sometimes displaying the optode array is not compatible with easily interpreting the data until you superimpose the optode locations onto a head or brain using an atlas viewer. If you have meaningful location data you may be better off going straight to the visualisation on the head/brain as the "demo" pos files are really just for people without the ability to measure locations of optodes. I hope this helps!

Rebecca

Hi Rebecca,
thank you very much for your prompt answer. That explains a lot and gives me confidence in our measured .pos files.
We wanted to use the original files because we used an adapeted 3x5 grid with one short-separation channel. Because Homer3 uses the info from the channel positions to determine which channel are short-separation and which not, I guess we have to get used to the strange look in Homer3 then but therefore we will be able to use the short-separation channels.
Thanks again!
Alex

Yep that makes sense - glad to have helped!