This question helps illustrate my question. In The Waste Lands, book 3 of Stephen King's The Gunslinger series, the ka-tet end up at the end of the beam guarded by Shardik, the bear. Now I assumed that the gunslinger's world was circular and that the end of the beam were at the edges of the world.
This means that during Roland's years of wandering he's managed to end up at the edge of the world i.e. as far from the Dark Tower as it is possible to be.
Given Roland's knowledge of the Beams, the guardians, the tower and the geography of his world, why did he not simply travel towards the tower from Gilead (or from wherever he started) until he picked up a beam and then followed that?
I'm currently listening to the books again and have studied the map on the linked questions and can find no logical explanation.
It may well be that events have simply conspired to guide Roland towards the Western Sea (his pursuit of the man in black, perhaps, taking precedence over his quest for the tower) and the doors from which he is to gather his ka-tet.
Ka - ka like a wheel...