Comment by 1718627440

I should have written that comment quite differently, it took a while for me to understand how it is read.

I did not say "train systems are ...", I said "trains are ...". This is referring to e.g. that odometry based on wheels results in a drift. GNSS is to imprecise and unreliable. I'm aware that you simply use balises, that's what I meant with "markers in the track". However that's based on the infrastructure again, so it's again not trains on their own.

https://news.ycombinator.com/item?id=50293093

It was simply supposed to be an example how GPS sounds like it should easily solve a problem, but does not without additional measures, that then do not need GPS anymore.