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How We All Became Little Blue Dots on a Digital Map

Katherine Dunn on the Intersection of Corporate and Military Power and That Created Modern GPS Systems

Via Bloomsbury Publishing

Katherine Dunn

June 17, 2026

As Taiwanese manufacturers rushed to fabricate GPS chips in the early and mid-2000s and sat-nav companies rushed to install them in their receivers, Frank van Diggelen and his colleagues at Global Locate were finessing another technical challenge. Making mobile phones trackable when they called 911 was one thing. But what if GPS chips in mobile phones could actually be useful outside of emergencies, for directions, in the same way as TomTom receivers in cars? This was a great idea in theory. But the chips were still too slow, and too power-hungry, to be much use as an everyday tool.<br>Article continues after advertisement

There was another concern, one very much based on human impatience: if it took too long for a receiver to "lock on" to GPS and determine its location—which was highly likely, since the GPS antenna in a phone is very tiny, the signal is very weak and the user is often inside a building—people tended to just give up. Van Diggelen figured he had about a couple of seconds to make a human stay.

Global Locate was a fabless chip maker, which meant it designed the chips that would go in all kinds of GPS-hungry products. It was in the middle of the supply chain, between the companies that made the chips—many of them in Taiwan—and the companies that needed the chips, like TomTom. And this was a design challenge.

The system van Diggelen and Global Locate designed to solve these problems is called "assisted GPS," and it’s basically a shortcut. To find its location, a phone’s chip first jumps back to the location of a landmark it most recently interacted with: a mobile phone mast, for example, or a Wi-Fi hotspot. The chip then cross-references the longitude and latitude of that location with the "ephemeris data," the precise guide produced by the US government on where all the GPS satellites are expected to be, and when.

The interlocking puzzle of the iPhone, GPS and Google Maps was a moment when multiple strands of technological development…converged into a single life-changing package.

If predicting a satellite’s orbit sounds familiar, it should. This is a more advanced version of what the Transit engineers were doing in the 1950s and 1960s with the orbits of the early satellites: predicting where they would go next, based on their understanding of time and the earth’s gravitational field. These orbits are produced at the GPS Control Center near Colorado Springs and are typically valid for four hours.

This head start meant the chip in the phone already knows exactly where to look. Instead of going "wide" to scan the sky for the satellites, it can "go deep," van Diggelen says, honing in on where the satellite is expected to be so the tiny antenna in the phone can pick up its whisper and magnify it to more than a hundred times its usual strength, all while minimizing the impact on data and battery life. It’s the equivalent of arriving in a new city, pulling out of the car park in a rental car, and using a Post-it note left on the dashboard to tune in to the exact radio station you’re looking for.

This jump-start meant a mobile phone could theoretically lock on to the GPS signal within milliseconds. And because the US had turned off selective availability, van Diggelen and his colleagues realized that Global Locate could produce their own ephemeris data for days into the future, not just four hours—so a mobile phone wouldn’t be reliant on constant connectivity. This is why, if you open Google Maps on your phone right after you arrive in a new location, you can see your general location (usually on a mostly blank map) even before you have local data coverage.

These are the first two pillars of assisted GPS: first, knowing where to look for the signal in advance, and second, having ephemeris data that is valid for a week into the future.

The third and most profound pillar...