A car GPS works by using signals from a network of satellites to calculate your exact position on Earth. Your car's GPS receiver picks up timing signals from at least four satellites. By measuring the tiny time differences in when these signals arrive, it can perform a calculation called trilateration to determine your latitude, longitude, and elevation. This raw location data is then plotted onto a digital map stored in the device or streamed via cellular data, which turns the coordinates into a visual location on a road, providing you with turn-by-turn directions.
The process starts with the Global Positioning System (GPS), a constellation of at least 24 satellites operated by the U.S. government, orbiting about 12,000 miles above the Earth. Each satellite continuously broadcasts its precise location and the exact time. Your car's GPS antenna receives these signals. Since the signals travel at the speed of light, the receiver can calculate the distance to each satellite based on how long the signal took to arrive.
However, distance alone from one satellite only tells you that you're somewhere on a giant sphere. Adding a second satellite narrows it down to a circle where two spheres intersect. A third satellite narrows it to two possible points. The fourth satellite is crucial for two reasons: it eliminates the incorrect point and, more importantly, it corrects any timing errors in the receiver's internal clock, which is not as precise as the atomic clocks on the satellites. This correction makes civilian GPS accuracy possible, typically within 5 to 10 meters under open sky.
Once your position is locked, the navigation software takes over. It compares your moving position to the digital road map. When you input a destination, the software's algorithm calculates the best route based on factors like distance, speed limits, and real-time traffic data (which is usually delivered via a separate internet connection). It then provides visual and audio instructions, constantly updating your Estimated Time of Arrival (ETA) as you drive.
| GPS System Component | Key Function | Example Data/Details |
|---|
| GPS Satellites | Broadcast precise time & location signals | 31 operational satellites in orbit (as of 2023), orbiting every 12 hours. |
| Receiver in Car | Calculates position via trilateration | Typically needs signals from 4+ satellites for accurate 3D location. |
| Positional Accuracy | How close the calculated position is to reality | 5-10 meters under open sky; can be worse in urban canyons or forests. |
| Time to First Fix | Time for receiver to determine location after startup | Cold start: 30-60 seconds; Hot start: 1-5 seconds (using saved data). |
| Map Data | Provides visual context for coordinates | Stored locally or streamed; updated periodically for new roads. |
| Real-Time Traffic | Adjusts routes based on current conditions | Delivered via FM radio (RDS) or cellular data connection (e.g., SiriusXM). |
