Up near udgaard where you'd find piles of corpses. You can't raise either undead at these places. Just wondering if that's supposed to be or what?

Otherwise the battlefields would work as a giant graveyard, for example.

There is, however, at least one place really close to Udgaard where you can raise undead. I'd go as far as to say every city with a necro guild in has a graveyard outside the city but close by.