Export gcps from Sentinel-1 GRD product


I am trying to extract the list of ground control points from the Sentinel-1 GRD product for georeferencing purpose. I know SNAP can automatically export ENVI gcp file (File->Export->Other->Geo-Coding as ENVI GCP file). But how are they created? Is it possible to extract the pixel positions as integers rather than decimals?

I noticed that in there are “geolocation grid points” in the xml file located in the annotation folder. Is geolocation grid point the same as the ground control point? If yes, I guess I can extract them them directly from the xml file.