GPS has always had to account for relativistic time dilation, it's the first human scale issue where relativistic correction became necessary. (This would be ge

GPS has always had to account for relativistic time dilation, it's the first human scale issue where relativistic correction became necessary. (This would be general relativity, incidentally, not special: it's the effect of the Earth's gravity on the atomic clocks in orbit.) But that's because the whole system needs absurd levels of accuracy to be useful at all: at 8 km/s of orbital velocity every source of error creates enormous error bars on the ground. I also know that NASA has experimented for years with satellites (even all the way up in GSO) using GPS signals for position-finding, so this is further out but not unprecedented work.