It is fake for now, but it I have some ideas.
First idea is to capture a render of the entire map at load time, and scale it proportionately. That way, the center of
the minimap is 0,0,0, and your position can be found by a mere division.
The second is to just draw it roughly and to the same trick.
The second is probably better, because I plan to use a lot of underground complexes;)
The method used in your examples, with the vislist is interesting too, but isnt quite what I plan.
I was going to do a simple "fog of war" on the map, but it would be screenshotted quite quickly, and made available by other players, so I seen no point:).