Before GPS: The Problem It Had to Solve
Long before satellites, navigators relied on ground-based radio systems like LORAN and Decca, developed around the Second World War. They worked, up to a point. The moment hills, buildings or bad weather got between a receiver and its ground stations, accuracy fell apart.
Militaries wanted something better: a way to know a vehicle's position anywhere on Earth, regardless of terrain. That single requirement, positioning that didn't care what was in the way, is the seed every satellite navigation system since has grown from.
Sputnik to Secret: The Cold War Origins
The moment that changed everything happened in October 1957, when the Soviet Union launched Sputnik, the first artificial satellite to orbit Earth. American scientists tracking its radio signal noticed something useful: the pitch of the signal shifted predictably as Sputnik moved, a phenomenon called Doppler shift. If you could measure that shift precisely enough, you could work out the satellite's position from the ground. Flip that logic around, and a satellite with a known position could tell a receiver where it was instead.
That insight became the basis for early US satellite navigation systems through the 1960s and 70s, developed under military control and kept firmly out of civilian hands. GPS as we'd recognise it today began launching satellites in the late 1970s, reaching Initial Operational Capability in December 1993 with a full constellation of satellites in orbit, and Full Operational Capability in April 1995. Both of these were purely US military milestones, declared by the Air Force Space Command, not the outcome of some international treaty. For years, that's exactly what GPS remained: a military tool, with no civilian use in mind whatsoever.
Opening the Gates: How Civilians Got In
It took a tragedy to change that. In 1983, Korean Air Lines Flight 007 strayed into Soviet airspace and was shot down, killing everyone on board. The investigation found that better navigation could plausibly have prevented the aircraft drifting off course in the first place. In response, US President Ronald Reagan announced that GPS would be made available for civilian use once it was fully operational, a genuinely significant shift for a system that had, until then, been considered purely military.
That promise didn't mean unrestricted access overnight. Civilian signals were deliberately degraded through a feature called Selective Availability, intentionally scrambling the signal so civilian receivers were far less accurate than military ones. During the Gulf War in 1991, the US military actually found itself short of dedicated military GPS receivers and had troops using civilian units instead, prompting a temporary reduction in that scrambling so soldiers on the ground could actually use the devices they had.
The Real Turning Point: Turning Off the Scrambler
Here's the part most histories of GPS skip entirely, and it's arguably the single most important date in the whole story for anyone using GPS today. On 1 May 2000, US President Bill Clinton ordered Selective Availability switched off completely. Overnight, civilian GPS accuracy improved roughly tenfold, from around 100 metres to about 20 metres.
Why did this actually happen? Partly because private companies had already found workarounds using differential correction services, so the restriction was becoming pointless. Partly because the US military had developed the ability to jam GPS regionally without degrading it worldwide, meaning a blanket global scramble was no longer strategically necessary. Whatever the exact mix of reasons, the effect was immediate and permanent. Every consumer GPS device, from a phone to a fleet tracker to a personal locator beacon, has benefited from that single decision ever since.
How GPS Actually Pinpoints You
People often assume GPS works like triangulation, using angles to fix a position. It doesn't. GPS uses trilateration, a different technique that relies purely on measuring distance.
Each satellite constantly broadcasts its exact position and the precise time the signal was sent. Your receiver picks up that signal and works out how long it took to arrive. Since radio signals travel at the speed of light, a known speed and a known time gives you a known distance, the radius of a sphere with the satellite at its centre. Do that with one satellite, and you know you're somewhere on that sphere. Do it with four, and the spheres intersect at a single point: your position.
Here's a genuinely clear explanation of the maths behind it, worth two minutes if you want to actually understand what's happening inside every GPS device you own.
Beyond GPS: The Multi-Constellation World
GPS was first, but it's no longer alone. Several other countries built their own satellite navigation systems, and understanding what's changed here genuinely affects which device you should buy today.
| System | Operator |
|---|---|
| GPS | United States |
| GLONASS | Russia |
| Galileo | European Union |
| BeiDou | China (formerly known as Compass) |
| NavIC | India (formerly IRNSS) |
| QZSS | Japan |
Together, these systems are known as GNSS, Global Navigation Satellite Systems, an umbrella term covering all of them. A modern receiver that combines signals from two or more of these constellations, GPS plus Galileo is a common pairing, gets a faster initial fix and holds up better in tricky conditions, like steep gorges or dense bush, where a single-system device might struggle to see enough satellites clearly.
This isn't a marketing gimmick. It's a genuine, measurable improvement, and it's exactly why the personal locator beacons and trackers worth buying today increasingly specify which systems they combine, not just that they "have GPS."
The NZ Angle: PositioNZ and Why This Still Matters
New Zealand isn't just a passive user of satellite navigation. Toitū Te Whenua Land Information New Zealand runs PositioNZ, a network of around 37 continuously operating GNSS reference stations spread across the country, run in partnership with GNS Science through the GeoNet project.
These stations collect data from GPS, GLONASS, Galileo, BeiDou and QZSS, and the network does two genuinely important jobs. It monitors how New Zealand's landmass shifts over time, useful given how seismically active the country is, and it provides free, high-precision correction data that commercial GNSS services build on. That correction data is what makes centimetre-level accuracy possible for surveyors, construction firms doing machine control, and precision agriculture operations levelling paddocks or mapping soil variation across a farm.
None of that precision would be worth much without the underlying multi-constellation approach this article has been building towards. A single-system GPS receiver from the 1990s simply couldn't deliver the accuracy modern NZ industries now rely on daily.
Real GPS-Enabled Gear from Mobile Systems
Here's where the history actually earns its keep. The devices below all benefit directly from everything covered above, particularly multi-constellation positioning.
For the full range, our GPS trackers and satellite devices collection covers everything from fleet tracking to backcountry beacons. If you're specifically weighing up a personal locator beacon, our EPIRB and PLB buyers guide goes into the practical decision in more depth.
