In GURPS, the Absolute Direction advantage really gives you a lot of bang for the buck. It's limited in ability, but within its niche it's basically foolproof. As the text says:
"You always know which way is north, and you can always retrace a path you have followed within the past month, no matter how faint or confusing." - GURPS Basic Set: Characters, p. 34
I have mixed feelings about this advantage.
For a game based on multiple dungeons, such as a dungeon-of-the-week game or a traveling game, this is mainly positive for both the players and the GM. The players don't have to worry so much about mapping, or getting lost - either above or below ground - as long as they keep their Absolute Direction-having PC conscious. The GM doesn't have to worry about folks getting lost on the way to the dungeon, or frittering away a good portion of a session working on their maps, or having suspension-of-disbelief issues with describing rooms ("There is a door in the West wall near the south corner" "How do we know it's the west wall? The stars? We're underground.") In my previous campaign, which ranged around a largish play area and where locations were fodder for one or two visits, and the overarching conflict is what the players were on about, this was fantastic.
For a megadungeon game, it's not quite as fun for the GM. Always know which way is north? Gets rid of lots of trick rooms and disrupts the fun of non-Euclidean geometry. It even makes mapping less of an issue, and turns "get out of the dungeon safely" from a test of player memory, player mapping, and player attention into "the scout has Absolute Direction and retraces our steps."
Not fun, in my opinion.
So I modified the advantage for this game.
Above ground, it works as advertised.
Underground, well, it's not so simple.
You keep the skill bonuses for things like Orienteering and Body Sense (great when you're teleported).
But you don't get the path retracing, nor the knowledge of north.
Instead, you get two things:
- exact distances. This is something I don't do by default. When I describe rooms and corridors to a guy with Absolute Direction, it's exact. Not "roughly 20-25 yards away is a big door." It's "20 yards away is a door that's 6' wide." Not "A rectangular room about twice as wide and three times as long as the corridor you entered by" but rather "a 25' wide and 35' long room." "He's kind of far away." No - it's "He's 17 yards away."
- recognition of places you've been before. Even if you come at the place from a different angle, or strange entryway, it doesn't matter. So long as it's other than a warping/teleporting method, I'll tell you if you've been there before. And roughly how recently ("You were here before today" or "you were here a few weeks ago.")
This isn't the letter of the advantage, but it preserves some of the spirit - you're less likely to get lost because your maps are potentially better. You can rely on the GM to tell you you're back in recently-explored territory. But it's still up to you not to get lost, to figure out if that room spun you around, or which way points closer to the stairs down. It's changing it from a more output-centered, automatic-success advantage vs. a narrow set of issues (getting lost) into a input-centered, automatic improvement in information quality advantage. It makes it something that's still 5 points of value in a game where knowing North underground and retracing steps automatically is clearly more useful than anything else similar to it that you can get for 5 points.
For a game where "explore the strange environment" is a good part of the fun and the challenge, I am finding it works very well indeed. All it takes is some re-jiggering by the GM and reasonable players who accept the change without griping. I've got players like that, generally, because I'm not nerfing their power but making it fit the spirit of the game better. They hate it when the scout isn't there and their map gets a little "off."