Scientists use the Global Positioning System (GPS) to plot precise measurements of plate position. Over 2,000 transmitters from around the world emit data to the satellites. Tracking the changes in positional data enables scientists to approximate plate motion relative to a network of geostationary satellites.

 

 

In this map, each of the green circles represents a transmitter. The yellow line indicates how that transmitter has moved over time. Longer lines represent more movement.