While thinking about the 3d mapping method (see here for the basics and here for an example), I remembered this post over at Hill Cantons about wilderness descriptions in rpgs and how problematic they are. I think I got an idea how to give this a slightly different perspective.
As a DM you might have something like this:
|Part of a Mystara Map in the Rules Cyclopedia|
|"Felsenmeer" in Germny (source)|
Here it gets problematic. For me at least. It isn't that I'm not able to make something out of it, but, using words only, it will never be as complex as the picture above. Or random, at that. But to get a random encounter into position, just take the group as point of origin and roll the coordinates* with a die appropriate for the distance. Let me illustrate:
With knowing the height difference, direction and distance, a DM can now improvise the surroundings from there (even if it's only a reminder, it is also random and fast). Same goes for interesting features the group might discover.
Landmarks and travel
I should do a post about 3D hexmapping in the near future (I got a few ideas while thinking about this, but anyway). For now let's just say, if one changes the dice for the coordinates to 1d100 yards (or more), one could place nearly anything, hidden or visible, when the group is exploring an area.
They are in a very dense forest and might get lost? A DM could use the same method as described under Navigation in my last post, only with the characters moving, not the ground. So the DM rolls for the movement and the leading characters wilderness survival check (or whatever) modifies the result into the direction the characters want to travel.
Negative results (moving downhill or backwards)
Here are different solutions possible. One is to take only half the result for every negative y and z result, another one would be to treat them just as positive results. In realtime travel, negative results might, for instance, mean complications, like "The trail ahead looks difficult, you might have to reroute...".
For Mountains, add a fixed number to y and ignore negative results everytime you roll it (if the group is going up, of course). And everytime the maximum for y comes up, roll a die with a smaller scale to indicate they are travelling downhill for a short period.
Edit: I lied about the Dolby surround, you'll have to run around the table and improvise...