What is GPS?
Has it ever crossed your mind when using Google Maps or Waze “how is this thing locating me? how does it know where I’m going and where I’m from?”
That question always intrigued me. During my early university courses at the Technological University of Panama, while studying Civil Engineering, I was lucky to have some great professors who opened my mind to how this technology really works and ignited my love for geographical and GIS systems. And it turns out, it’s mostly math, mixed with some clever ways to interpret our reference point on this blue globe we call Earth.
Down the road, I’ll share sources you can check and validate, but mostly I’ll focus on how things actually work, simple, visual, and straight to the point.
Origins and How Satellites Triangulate Positions
Modern GPS technology dates back to the early 1970s. Like many major innovations, it started as a military project developed by the U.S. Department of Defense. Whatever the motives were, that need gave birth to a wave of brilliant minds who made the complicated simple.
So… how does GPS actually work?
Let’s picture an imaginary cornfield 🌽.
You and I are standing somewhere in it. The corn is tall, we can only see each other if we’re at least five meters apart. The challenge? Figure out exactly where we each are.
Step 1: One flag
We plant a red flag somewhere in the field. You tell me, “I’m 20 meters from the flag.”
I reply, “I’m 50 meters from the flag.”
Cool, now we both know how far we are from the flag. But there’s a problem: you could be anywhere on a 20-meter circle around it, and I could be anywhere on my 50-meter circle. We still don’t know where we are relative to each other.
Step 2: Two flags
We add a second flag. Now we each measure our distance from both flags.
Where those two circles overlap, that’s our possible zone. It’s closer, but still not exact. There are two possible intersection points.
Step 3: Three flags
Add one more flag, and the magic happens. 🎯
The point where the three circles meet, that’s your exact location.
Congratulations, you just triangulated yourself in the cornfield (in 2D, at least)!
From the Cornfield to Space
That example gives us a 2D way to find a point on a flat plane.
In our real, 3D world, the concept is the same, except instead of circles, we’re dealing with spheres, and instead of flags, we have satellites orbiting Earth.
Rule of thumb:
- 2D → 3 reference points (circles)
- 3D → 4 reference points (spheres)
Why four?
Because in 3D space, each sphere contains an entire surface of possible points.
- 2 spheres intersect in a ring
- 3 spheres intersect in two points
- 4 spheres narrow it down to one single point
And that’s exactly what GPS does, except with satellites instead of flags.
Each satellite sends a signal with precise timing, and your device calculates where those signals intersect in 3D space to determine your exact position.
Quick Note: GNSS vs GPS
Before diving into the math, let’s clarify a common confusion.
- GPS is just one system, the U.S. version.
- GNSS (Global Navigation Satellite System) is the umbrella term that includes GPS (USA), GLONASS (Russia), Galileo (EU), and BeiDou (China).
Most modern devices today use GNSS, which means they connect to multiple constellations at once giving better accuracy and reliability.
At first, I thought GNSS was another technical monster, but it’s really just the same idea with a fancier badge.
Branding wins. 😄
🧮 Next Up
In the next post, we’ll dive into how coordinates are represented, decimal degrees, degrees-minutes-seconds, and why converting between systems isn’t as simple as it sounds.
We’ll also take a peek under the hood at how tools like my GPS Converter process those numbers in real time.