How Does Your Phone Know Exactly Where You Are?
How Does Your Phone Know Exactly Where You Are? — Even when you can't see it, just a few clues of "distance" narrow the answer to a single point. The triangle you drew in school was quietly finding you on planet Earth.
Even in an unfamiliar town, open a map app and a blue dot marks "you are here" precisely. How does your phone know where you are? Nobody is watching you.
Picture an old ship in the middle of the ocean — water in every direction. How do you know where you are? Old sailors guessed by the stars; the height of the North Star told them north–south. But east–west was hard, and countless ships were lost. "Knowing your exact location" was one of humanity's oldest puzzles.
The secret is the triangle. Suppose three friends each say "you're 100m from me." With one friend, you only know you're somewhere on a circle around them. With two, the candidates shrink to two spots; with three, they meet at exactly one point! That's triangulation. In GPS, satellites in the sky play the role of friends. The time a satellite's signal takes to reach your phone gives the distance to it, and with 3–4 satellites your spot on Earth is pinned to a single point. Since signals travel at light speed, there's also math that turns time into distance.
- The blue dot in maps and navigation (GPS)
- Real-time tracking of delivery riders and taxis
- Find-my-phone, smartwatch location sharing
- Locating an earthquake's epicenter uses the same triangulation
測 (cheuk) comes from measuring the depth of water (氵) with a ruler — the 測 of "measurement, observation." GPS gauging unseen distances to find your position is exactly the math of 測.
Meet this hanja in Cheonjamun →Even when you can't see it, just a few clues of "distance" narrow the answer to a single point. The triangle you drew in school was quietly finding you on planet Earth.
