How Does GPS Calculate Time?

GPS calculates time by using atomic clocks in satellites and the concept of relativity to provide precise timestamps for positioning. 

Every GPS satellite carries ultra-accurate atomic clocks that broadcast time signals. A GPS receiver on Earth picks up these signals from multiple satellites and calculates how long each took to arrive, using the differences to determine location and current time.

GPS tracking is an important feature in many time tracking solutions and even in crew scheduling software for construction production tracking, especially tracking crews working on projects. And it helps to understand how it works, so here it is in a nutshell:

Atomic Clocks in Satellites

GPS satellites are essentially flying time beacons. Their clocks are accurate to billionths of a second. They continuously transmit their time and position.

Signal Travel Time

Your GPS device receives these time-stamped signals. Because the signals travel at the speed of light, there’s a tiny delay from when the satellite sent it to when you get it. By multiplying that signal travel time by the speed of light, GPS can calculate how far away the satellite is.

Triangulation for Position

By getting distances from at least four satellites, the GPS receiver can trilaterate your exact position (latitude, longitude, altitude) and also synchronize the time. Essentially, solving these distance equations yields your 3D position and the precise time.

Relativity Adjustments

One wild aspect is that GPS has to account for Einstein’s relativity. The satellites’ clocks tick slightly differently than ground clocks because they’re moving fast (special relativity) and are high above Earth’s gravity (general relativity). 

Engineers apply corrections so that the time signals remain accurate to ground observers. Without these adjustments, GPS timing would drift and positions would be off by kilometers!

So, GPS time is a global standard delivered from space. It’s why your smartphone or a workforce time clock that uses GPS can timestamp events (like clock-ins) with split-second precision anywhere in the world. 

In construction or pull planning of projects, for example, site managers might use GPS time-stamped photos to verify when a phase was completed.

Interestingly, GPS time doesn’t account for leap seconds and has been ticking continuously since January 1980. It occasionally needs to sync with our civil time (UTC). 

But overall, GPS has become the backbone for timekeeping—telecommunications, power grids, financial networks, and of course navigation, all rely on these satellite-delivered timestamps.

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