GPS / GNSS
Also known as: GNSS, GPS receiver, A-GPS, RTK GPS, GLONASS, Galileo
GPS (Global Positioning System) is the US satellite navigation network.
Your phone or GPS device receives timing signals from at least 4 satellites, calculates the distance to each, and triangulates its position. GNSS is the broader term covering GPS plus Russia's GLONASS, Europe's Galileo, and China's BeiDou.
GPS / GNSS, explained at three levels
At home
GPS uses satellites orbiting Earth to tell your phone where you are. Each satellite sends a time signal; your phone measures how long the signal took to arrive. Knowing the speed of light, it calculates how far away each satellite is, then figures out where on Earth you must be.
At work
GPS powers the location features in every app that knows where you are -- navigation, ride sharing, food delivery, and fleet tracking. Understanding GPS limitations (poor signal indoors, delay in cold-start acquisition) helps explain why these apps sometimes behave unexpectedly.
At home
GPS accuracy in consumer devices is typically 3-5 meters under open sky. Accuracy degrades in urban canyons (tall buildings block signals) and is unavailable indoors. A-GPS (Assisted GPS) speeds up initial fix by downloading satellite almanac data over the internet rather than waiting for it over radio. Modern phones combine GPS with GLONASS, Galileo, and BeiDou for faster locks and better accuracy.
At work
GNSS is used in precision agriculture (centimeter accuracy with RTK corrections), autonomous vehicles, fleet tracking, asset monitoring, and timestamping financial transactions (GPS time is accurate to nanoseconds). GNSS receivers are small, cheap chips embedded in almost every smartphone, tablet, and many IoT devices.
At home
GPS positioning requires at least 4 satellites for 3D position and time solution (latitude, longitude, altitude, and receiver clock error). The signal uses spread-spectrum radio (CDMA), with each satellite broadcasting on the same frequency but with a unique PRN (pseudo-random noise) code. The receiver correlates incoming signals against known PRN codes to identify satellites and measure pseudoranges.
At work
RTK (Real-Time Kinematic) GPS achieves centimeter-level accuracy by comparing phase measurements between a base station at a known position and a rover receiver. SBAS (Satellite-Based Augmentation Systems -- WAAS in North America, EGNOS in Europe) broadcast differential corrections via geostationary satellites, improving civilian accuracy to under 1 meter. GPS jamming and spoofing are growing concerns for critical infrastructure, aviation, and autonomous systems.
Real-world examples
At home
Sophie uses GPS on her phone to navigate while cycling. When she goes into a tunnel, navigation freezes briefly -- GPS signals can't penetrate underground, so her phone switches to dead reckoning (using motion sensors) until she emerges.
At work
Carlos's logistics company tracks 200 delivery vehicles using GNSS trackers that report location every 30 seconds. Analysts use the data to optimize routes, verify delivery times, and detect unauthorized vehicle use.
Common confusions
- GPS works everywhere, including indoors — GPS signals are very weak and easily blocked by buildings, metal, and the Earth itself. Indoors, phones use Wi-Fi positioning, cell tower triangulation, and Bluetooth beacons as GPS substitutes -- often with reduced accuracy.
- GPS is always precise to a few centimeters — Standard GPS is accurate to 3-5 meters. Centimeter accuracy requires RTK differential corrections, specialized receivers, and base station infrastructure -- used in surveying and agriculture, not consumer devices.
For analysts
GPS/GNSS data from fleet tracking, delivery apps, or customer apps is a rich source for business analysis -- measuring delivery time accuracy, identifying inefficient routes, and analyzing geographic customer distribution.
History & origin
GPS was developed by the US Department of Defense starting in the 1970s, with the full constellation of 24 satellites declared operational in 1995. Originally restricted for civilian use to a degraded accuracy (Selective Availability), GPS was opened to full civilian accuracy in 2000 by executive order. Smartphones with GPS receivers transformed navigation from specialized devices to ubiquitous features. Modern devices receive signals from multiple GNSS constellations simultaneously for better accuracy and reliability.