Ah, I didn't see WolframAlpha in your question and so I incorrectly assumed you were using Mathematica.
I am impressed with the query you found that it understands. I would never have guessed something like that.
I'm sorry, but usually my experience with WolframAlpha is about the same as yours, by trial and error I can get something out of it, but it isn't really what I wanted and usually no amount of trying to guess what word to give it will give me the answer I'm really looking for. I tried "base", I tried "altitude", I tried "height", I tried "width", I gave up. Sorry.
