So when you upscale a DVD to HD and the pixels match perfectly doesn't that mean that the correct ratio of a* widescreen DVD is in fact 1024x576.
True, but only if by "a" you mean "this particular" ;) I guess this is just the way they do things these days (ignoring what is admittedly an archaic and outdated - but still valid - standard), but if you find a DVD with thin black bars at left/right, that'll be NAB and you should definitely take it into account in that case.
DE