The financial system, too: banking, stock trading (especially the high-frequency computer drive stuff) and so forth. Hedge funds and Wall Street types would be in a world of hurt without GPS.
...
So, there would at least be a silver lining.
I have a general distrust of things electronic, probably as a side-effect of spending most of my adolescence and adulthood dealing with electronic devices that were misbehaving.
My first "formal" electronics training was in avionics (although it was so long ago that we might as well be talking horses and buggies by way of analogy), but I've been farting around with electronics in general since I was 6 years old. I've always been impressed by the variety of ways in which electronic devices can go bad, and the advent of digital processing has added a whole 'nuther set of opportunities for failure in addition to the old-fashioned ones that afflicted the analog devices that dominated when I was trained.
Nonetheless, I have to admit that the GPS system in general is one of the better-behaved clans of electronic devices. That it's administered by the government makes it all that more amazing that it works as well as it does, as consistently as it does.
Still, I find it a bit disconcerting that so many pilots (both aeronauts and mariners) have come to depend on GPS as much as they do, considering that it's a relatively recent technology that didn't even exist (except in a seminal, theoretical sort of way) when I took my first flying lesson, or when I sailed the seas.
Just as an aside, does anyone know if mariners even have to know celestial navigation any more?
All of this has become pretty much a moot issue for me since I went rogue. Most of my flying is in ultralights these days, and they just don't have the range for me to need much in the way of navaids. I'm familiar enough with these hills and the rivers, streams and highways that criss-cross them that eyeballs and a sectional are enough for me to find my way around just fine.
But even before I went rogue, I shunned glass cockpits and pretty much ignored the GPS (along with anything else that the J3 Cub that I first flew didn't have). I find it a bit disconcerting that so many pilots have come to depend upon GPS as much as they do.
-Rich