Being a writer...
Being a writer, I pride myself on being able to come up with plausible answers for questions like this. True, if I'd been the writer of the original
Stargate movie I don't think I'd have done it quite the same; ie, that annoying bug would be gone, along with several others -- but then, most writers aren't perfectionists and don't know a lot about physics etc. So let's see.
Aside from the fact that, in the movie, they developed the software for using the stargate but
hella fast (I want that programmer working for me!), it is possible that, since they can tie into the gate with the computer, the gate can tell the computer certain things.
One explanation for knowing the coordinates, therefore, could be that the gate simply
tells the computer where the current terminus point is. This is the simplist, and therefore my preferred, solution. It also means that the computer would have a reason for saying "demolecularisation in progress", and show that nifty little graphic. Realistically, a computer should
not be able to tell you that,
or when the object is going to exit the wormhole (although, for the latter there could be a constant time for an object to travel through, so you could simply do a count-down.) In fact, gate/computer communication would probably solve a lot of nits in both the
Stargate movie and series, and there is that "intuitive" function it has built in, slipped by Carter in the late third or early fourth season as what was obviously a subtle attempt at defence of teh wormhole's amazing ability to know exactly when to close.
Now, as for the two-dimensional board -- well that idea was just so stupid that there
is no defence
I suppose it could be argued that it's all they had available, or that they used it because it was more convenient than a gigantic sphere sitting somewhere. Technically, they could just track the position of the planets in two dimensions instead of three; ie, their distances from the galactic core along the horizon plane of the galaxy. I'm not sure if that board actually shows only our galaxy or if it has others as well. Certainly, there is a lot of contradiction in terms of how far the wormhole actually goes -- in the movie I believe it was "millions" of light-years, and the series sometimes says the same thing. However, our galaxy is only 100 thousand light-years in diameter, so that means that a lot of the planets they visit must be in other galaxies. Some, on the other hand, are close to Earth -- in the fourth season episode
Prodigy Sam says that the planet involved is only 42 600 light-years from Earth. This presents another problem, however, since to visit Thor's homeworld of Idah, which is in another galaxy,
eight chevrons were required, and additional power. Now, I'm not saying that Thor's galaxy is only a couple of million light-years away -- the nearest galaxy is 3 million. However, it does raise an interesting question.
Having said all that, let's not even go
near the occasionally-used "other universe" idea. Every now and again somebody will say the Stargate leads to another universe. It doesn't. I wish writers would get their facts straight and bother to do research instead of just making assumptions...
