I'm including a vowel chart in a linguistics document of mine, similar to this, and while I'm aware that there are a couple of packages (TIPA, pst-vowel) that can do the job, I'm interested in trying to draw it using PGF/TikZ. Having not used TikZ before, I'm a little unsure on where to start with this deceptively simple figure.
As I understand it, I'd need to define some kind of skewed grid with [default] nodes at the line intersections, their midpoints, and the middle of each "square". The actual letters would then be drawn on top, positioned by coordinates; at the moment I'm not interested in arbitrary positioning of letters as occurs in the diagram.
Can anyone help me out?