That's honestly getting to a point I only know vaguely about -- my real-world experience is just from chatting with surveyors when I needed to get a couple of p

That's honestly getting to a point I only know vaguely about -- my real-world experience is just from chatting with surveyors when I needed to get a couple of parcels of land surveyed (once for a boundary survey, wherein I'm not sure this came up, and once for a FEMA/flood zone survey, where matching the site data to the FEMA data was much more important). Part of the answer, in the US, (and the expensive equipment -- one of the smaller surveyors I talked to just rented it on an as-needed basis) are the Continuously Operating Reference Stations, which is a network of ground-based stations of defined positions which are used to refine GPS coordinates relative to the National Spatial Reference System: https://www.ngs.noaa.gov/CORS/ https://www.ngs.noaa.gov/CORS/