Norion Ironaxe:
I don't have my handbook with me now so can't check, but I thought Dwarves could tell North underground, maybe I'm just making that up but it rings a bell???
I also thought dwarves possessed that ability, but it is not listed in 1st edition. I just checked in the 3e book and it was not there either. It might be in 2e or 4e, but I am not sure. I could dig out the books later and check.
I do know there is a 0-level 3e spell (Druid, Bard) called Know Direction.
I don't have Unearthed Arcana anymore, anyone know if maybe it is a barbarian class ability in 1e?
At any rate, given what we do know, I was going to suggest Norion's dwarf stonecunning ability would apply here and assign a 3 in 6 (50%) chance of detecting direction underground.