Blog
Patrik Pasko
August 25, 2026
If you wonder how telco operators and police departments locate your SIM card, the answer is trilateration and triangulation.
It is simple geometry pin-pointing a phone using signal distance. No GPS required. The network already knows which towers can hear you, and from that it can reconstruct where you must be standing.
These two words get mixed up constantly. They are related, but they are not the same.
• Trilateration uses distance. Each tower estimates how far away the phone is (from timing, signal delay, or power). Draw a circle with that radius. Do it from three towers and the circles meet at one point.
• Triangulation uses angles. Towers measure the direction the signal arrived from. Two bearings are enough to cross on a map.
Cell networks use both. The three-circle picture is trilateration. That is the method we break down below.
1 tower: Gives a distance radius. Knowing you are somewhere on a circle 10 km wide isn't very helpful.
2 towers: Intersects two circles, narrowing the location down to just two possible spots.
3 towers: Adds the final circle. The single point where all three overlap is the exact location.
Cell towers get you to a neighborhood. Indoor walls, reflections, and sparse rural towers all limit how tight that circle can get. For room-level accuracy, phones switch to a denser set of radio beacons: Wi-Fi access points.
Google maintains a massive background database of Wi-Fi IDs paired with GPS coordinates, constantly updated by Android phones passing by, even when sleeping. When a device scans nearby Wi-Fi networks and measures their signal strength (RSSI), it checks those IDs against the database.
RSSI is not a perfect distance meter, but with several known access points it is another trilateration problem: stronger signal, closer AP. Combining Wi-Fi signals with cell tower trilateration narrows the location down from a general neighborhood to the exact room you are standing in.
The math does not change when you walk into a factory. BLE beacons, UWB anchors, and Wi-Fi APs are just towers with shorter range. One anchor gives a radius. Two leave a pair of candidates. Three pin a point.
That is why indoor RTLS and outdoor cell location look different in hardware, but share the same geometry. If you want the industrial version of this stack, start with our guide to RTLS technologies.
