GNSS

How does GNSS find a position?

A GNSS receiver finds its position by measuring how long signals from several satellites took to arrive. Each satellite broadcasts its position and the time. With signals from enough satellites, the receiver can work out where it is and what time it is.

Using more than one constellation gives the receiver more satellites in view and better geometry, which helps most where part of the sky is blocked. That is why a phone or badge that reads GPS plus another system often fixes faster than one that reads GPS alone.

GPS

The system run by the United States.

Galileo

The European Union's system.

GLONASS

Russia's system.

BeiDou

China's system.

Where does GNSS struggle?

GNSS struggles wherever buildings, structures and trees block the sky. GPS.gov says a phone is typically accurate to within about 4.9 meters under open sky, and that accuracy worsens near buildings, bridges and trees. Inside a building the signal is often too weak to use at all.

What does GNSS mean for a jobsite?

On an open site GNSS gives a good reading of which jobsite a worker is at, and it is the main way a worn device finds its place outdoors. Indoors and in structures under construction, it is usually paired with another method such as Wi-Fi positioning, with the method and confidence kept for each reading.

A position from GNSS feeds a geofence time clock, which compares the reading to a boundary drawn around the site.