How GPS Works: A Plain-Language Guide
GPS watches and handhelds can feel like magic, but the underlying idea is fairly simple. Here's a general walkthrough of the concepts behind them.
The receiver listens to satellites
A GPS receiver picks up timing signals from multiple orbiting satellites and uses the small differences between them to calculate a precise position.
More satellites generally mean better accuracy
The more satellite signals a device can see and use, the more accurate and stable its position fix tends to be.
Position changes over time become pace and distance
By tracking how your position changes second to second, a device can calculate metrics like distance covered, pace, and elevation change.
Some environments are harder than others
Dense forests, deep canyons, and urban areas with tall buildings can all reduce GPS accuracy temporarily, since they block or reflect satellite signals.
Common questions
Why does GPS take longer to lock indoors or near tall buildings?
GPS relies on a clear view of the sky to receive satellite signals. Buildings, dense tree cover, and canyons can all weaken or block those signals, slowing down or reducing the accuracy of a location fix.
What's the difference between GPS and other satellite systems a device might use?
GPS is one satellite navigation system, generally operated by the United States; other regions operate their own systems. Many modern devices can use multiple systems together to improve accuracy and lock time, depending on the specific device's capabilities.