Civil and mining engineers have been making use of centimeter-accurate GNSS configurations for years now. The equipment necessary costs a few thousand dollars, more if you need even more precision. Most major civil and mining engineering projects use self-guided earth-moving equipment, not feasible without this technology.

The problem for homeowners is that surveys aren't enough. The vast majority of land titles are not registered in precise coordinates; they're registered in terms of landmarks, benchmarks, and so forth. This is changing at a glacial pace, but for now, the tech isn't the problem.

RTK has an accuracy of around 1cm. Its widely used by surveyors (and other things like agriculture, construction machine control, etc).