Is this the kind of thing that makes Google's Spanner database possible?
(If you try to calculate the offsets between two clocks by using something like NTP to measure round-trip times over the internet, you're implicitly assuming that packet delays in both directions are symmetrical.)
I wonder if we could get away by just building it and accounting for the error using some multiplier, without understanding the concept of relativity. I.e., how we would build it if we invented satellites before relativity.