Originally Posted by
D driver
and so why not D?
Ephemeris data is not position data. As an analogy, if I were to say that I was an hour south of Birmingham on the M5 with an average speed of 60mph, I have not given you position. What I have given you is the ability to calculate my position if you have knowledge of the route of the M5. You need more than just what's in the message, even if in the satellite's case it is an understanding of standard orbital mechanics.
As for time, well then we are talking abstracts.