So back in the 1990s, online I talked with someone who worked in the GPS constellation. He said that they wanted multiple passes of a Navstar over their trackin

So back in the 1990s, online I talked with someone who worked in the GPS constellation. He said that they wanted multiple passes of a Navstar over their tracking locations to correct the orbital parameters after every orbital burn. Since they were in MEO, drag was a smaller deal, so burns were infrequent. In LEO drag was so much larger that regular burns are necessary. However, on reflection I don't know the precision of the Hall Effect thrusters that the Starlink satellites are using. If they are precise enough in their thrust application then the only thing you'd need to observe would be the effects of exoatmosphere drag, which are still a big deal. Steve's operational experience was only with chemical thrusters, electricals were still bleeding edge in the 1990s. Basically, because of drag MEO will always be >>> than LEO for navigation purposes. That's why all the dedicated navsats are there! It is possibly to piggy-back and get a large enough scale to compensate for the loss of accuracy. Eyeballing satellitemap.space for my location (roughly 35N), it looks like you'd get a zenith every minute or two from Starlink. Again, fine for stationary, not sure about moving, given the need for multiple zeniths to correct uncertainty. As for the laser link SpaceX is very tight-lipped about that as far as I can tell, and that is one where the precision is all going to be measured operationally. Something like LAGEOS shows that it is possible to do things incredibly precisely with light, but the question is, does Starlink have the mass, energy, and compute budget to actually do it in practice.