Accuracy will depend on whether/to what degree SpaceX commits to providing a positioning, navigation, and timing (PNT) service.
The technique used in the article is quite powerful and general, but it does have certain drawbacks too. One advantage is that it is relatively insensitive to errors in the ephemeris. The path we are exploring relies more heavily on the ephemeris, as you speculate; but these can be really quite excellent, even in the sub-meter range. Actually the bigger source of uncertainty for absolute positioning using non-Doppler techniques will probably be clock errors. For Doppler, integration time/time-to-first-fix is a sticking point, unless you have 8+ satellite signals, IIRC.
We think accuracy in the low single digit meters is not too much of a stretch (note that I am making a claim about a rather different technique than the one in the article... nothing worth doing is ever totally straightforward!).
I understand that SpaceX ephemerides they publish are more accurate than the typical two-line element set. But the TLEs using the SGP4 propagator typically have errors on the order of 10s to 100s of meters [0] (and more, the further you are from the ephemeris time). Is the estimation really enough to get to down to the meter or sub-meter accuracy? Is that why it really requires 8+ satellites to get a good fix, i.e. it takes that many measurements to reduce your variance and GDOP?
The technique used in the article is quite powerful and general, but it does have certain drawbacks too. One advantage is that it is relatively insensitive to errors in the ephemeris. The path we are exploring relies more heavily on the ephemeris, as you speculate; but these can be really quite excellent, even in the sub-meter range. Actually the bigger source of uncertainty for absolute positioning using non-Doppler techniques will probably be clock errors. For Doppler, integration time/time-to-first-fix is a sticking point, unless you have 8+ satellite signals, IIRC.
We think accuracy in the low single digit meters is not too much of a stretch (note that I am making a claim about a rather different technique than the one in the article... nothing worth doing is ever totally straightforward!).