GPS receivers sold in the civilian market must disable themselves if they detect speeds above 1,000 knots (1,150 mph) or altitudes above 59,000 feet. These restrictions, known as CoCom limits, exist to prevent civilian GPS technology from being repurposed for weapons guidance systems.
Why Your GPS Has a Secret Speed Limit
Somewhere inside your smartphone, fitness watch, or car navigation system lurks a tiny safeguard you'll never encounter—unless you happen to be building a missile. Every civilian GPS receiver on the planet contains built-in restrictions that force it to stop working under certain extreme conditions.
They're called CoCom limits, and they exist for one reason: to keep everyday GPS technology out of weapons.
The Numbers That Trigger Shutdown
If a GPS receiver detects it's traveling faster than 1,000 knots (about 1,150 mph) or climbing above 59,000 feet, it disables itself. These thresholds aren't arbitrary—they represent the performance envelope where civilian applications end and military ones begin.
Your morning jog? Safe. Commercial airline flight at 35,000 feet and 575 mph? No problem. But strap that GPS to something moving at Mach 1.5 at the edge of space, and it goes dark.
Cold War Origins
The name comes from the Coordinating Committee for Multilateral Export Controls (CoCom), a Cold War-era organization that restricted Western technology exports to communist bloc countries. Though CoCom itself dissolved in 1994, its GPS restrictions live on through the Wassenaar Arrangement, an international agreement among 42 nations.
The concern was straightforward: GPS dramatically simplifies guidance systems. Before satellite navigation, building an accurate long-range missile required sophisticated inertial navigation systems costing millions. A $20 GPS chip could theoretically do the same job.
How Manufacturers Implement It
Here's where it gets interesting. The regulations require disabling when both limits are exceeded simultaneously, but many manufacturers play it safe:
- Conservative approach: Disable if either limit is exceeded
- Strict interpretation: Only disable when both conditions are met together
- Aggressive filtering: Some units won't even track objects approaching the limits
This inconsistency has caused headaches for legitimate users. High-altitude balloon enthusiasts, amateur rocket builders, and even some aerospace researchers have found their GPS units unexpectedly going offline during perfectly legal projects.
Does It Actually Work?
Security experts debate the effectiveness. A determined adversary with resources to build a ballistic missile could likely source military-grade GPS or develop alternative navigation systems. The restrictions mainly prevent casual misuse and add friction to weapons development programs in countries with limited technical capabilities.
Some argue the limits are security theater—a feel-good measure that inconveniences hobbyists while doing little to stop nation-states. Others counter that every obstacle matters when the goal is preventing proliferation.
Exceptions Exist
Military GPS receivers don't have these restrictions, obviously. And manufacturers can obtain licenses to sell unrestricted units for specific applications like aerospace testing or scientific research. But getting approval requires demonstrating legitimate need and implementing strict end-user controls.
So next time you're navigating to a restaurant, remember: your phone contains a tiny failsafe designed to keep it from guiding a warhead. It's a strange intersection of consumer electronics and nuclear nonproliferation—and it's been there all along, quietly watching your speed and altitude.