We’ve all been there: you’re in your 2006 Honda Civic at an altitude of 60,000 feet,
cruising along at 1,200 miles per hour on your way home from work.
But all of a sudden, your GPS shuts down, and now you have no idea how to get home.
At first this sounds like it’s probably a technical limit, right?
The chimpanzees that they put in the satellites to watch your car with high-powered telescopes
just can’t keep up past a certain speed or at a certain altitude.
But that’s not quite right—your GPS would theoretically work just fine at 1,200 miles
per hour or at 60,000 feet.
The actual answer is much weirder—your GPS manufacturer set those seemingly impossible
limits on purpose because they wanted to stop you from starting a thermonuclear war… technically.
Let me explain.
The Global Positioning System, as a service, isn’t just some free utility that was handed
down to us by God; it was actually created by the only force more powerful than God:
the US Department of Defense.
You see, in the early 1970s, the US was having a little trouble keeping track of all of its
nuclear submarines, which, y’know, are not the kind of thing you want to lose track of.
At the time, these submarines were being tracked with a satellite navigation system called
“Transit,” which worked a whole lot like GPS—a submarine could calculate its approximate
location on Earth by measuring its distance from two or more Transit satellites.
But this system had a bit of a problem: there just weren’t enough satellites to go around.
At any given time, the system would use five satellites to cover the entire Earth, and
that meant that most of the time, a submarine would only have line-of-sight to one of them.
It was still technically possible to calculate a rough location with the measurements from
one satellite, but that involved a whole bunch of convoluted physics and math stuff that
I don’t really have time to explain, so I’m just gonna put up a screenshot of a
Wikipedia article here for exactly one second and you can go ahead and pause the video if
you’re into that kinda stuff.
Now for all the people who didn’t pause the video because they’re cool and hate
science, the main takeaway was that this system technically worked but… not very well.
The US military needed something more reliable for their submarines, so they rolled out the
system we use today: Navstar GPS.
There were more satellites, with more accurate equipment, and a modern GPS receiver almost
always has line-of-sight to at least four satellites on even the most remote locations
on Earth.
Yes, even in Ohio.
But here’s the thing: when the Department of Defense spent billions of dollars developing
GPS, it wasn’t meant to be a public worldwide utility that made everyone’s lives easier
and more convenient.
In fact, there’s a whole section in the constitution prohibiting that.
For the first year that the system was in use, it was completely classified—not only
did the public not have access to it, they didn’t even know it existed.
And that’s because, at least at the time, the big technological advancement of “knowing
where stuff is” was really dangerous; knowing where your submarines are, knowing where your
missiles are, and knowing where the people you want to blow up are are all important
ingredients in… blowing people up.
No other country had access to this kind of global positioning technology, and the US
was not eager to give it up.
But, fast forward to September of 1983—this flight, Korean Air 007, accidentally drifted
into Soviet airspace on its way from Anchorage to Seoul, got shot down, and everyone on board
was killed.
Now, it was pretty obvious that this incident could have been avoided entirely if the US
government had made GPS accessible to civilians and private airlines.
The president at the time, Ronald Reagan, was probably a little conflicted—on one
hand, killing innocent people was his favorite pastime, but on the other hand, he was almost
up for reelection.
Making GPS public in 1983 wouldn’t be as big of a national security issue as it was
when it was first rolled out; the Soviet Union had already launched their own GPS system,
GLONASS, the year before, so it didn’t really matter if they got their hands on Navstar.
So, two weeks after the Korean Air incident, Reagan opened GPS to the public, but this
came with a couple of security caveats.
The first was that the signal would be partially scrambled, making it only accurate within
about 300 feet or 100 meters.
That way, if someone was going to nuke the White House, they might miss by a little bit.
This restriction was later overturned by Bill Clinton in 2000, because he wanted young people
to think he was cool.
Now, the other main caveat was put in place by the Department of Commerce, and it was
this.
Basically, any GPS receiver that was exportable—meaning that it could be sold outside the US—would
need to put height and speed limits in place that would shut it down if it were attached
to a ballistic missile.
These limits have been hard-coded into pretty much every GPS ever since; some shut down
at 1,200 miles or 2,000 kilometer per hour or above 60,000 feet or 18,000 meters, and
some shut down only when both limits are reached…
even though that’s technically not how the law is written, but whatever.
The big question is… do these limits actually affect anyone?
And the short answer is not really—that’s kind of why they’re still in place; they
don’t bother anyone, and there isn’t really any point in getting rid of them.
But the long answer is yes, they affect a very specific group of nerds who like to send
balloons to high altitude so that they can learn what cold garlic bread tastes like.
But until those nerds work up the confidence to write a letter to the Department of Commerce,
you’ll have to keep your car under 1,200 miles per hour.
So, okay, your phone can’t track your location at 60,000 feet.
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