high ridge front stitch

This is a stitch in an Iran afghan. The pattern says it is stitches you know, use with a technique that makes the pattern unique. So I need to know how to do the high ridge front stitch. I am only assuming however that my best guess would be that it is a front post double crochet done only in the front loop? And a low ridge front stitch is a sc front post in the front loop.
any help would be greatly appreciated.