Getting Pixel Spacing on ALOS2


I am working with snap for calibration and terrain correction of ALOS PALSAR2 data. I’ve a lot of images to deal with, so I’d like to use a tool like gpt.
I’d built an xml graph containing the instructions (I did it just by saving my hand made actions) BUT on the xml file it is required the pixel spacing, but I’d not seen this value anywhere on the metadata of the alos file.
So my question is how snap calculates the pixel spacings? (Source pixel spacings, see the screenshot).

I’d run gpt without pixel spacings and results are very different.
Any help would be much appreciated.