RLG – Ring Laser Gyroscope

A ring laser gyroscope (RLG) is a highly sensitive optical instrument that measures rotation based on the Sagnac effect, detecting frequency differences between two counter-propagating laser beams in a closed optical cavity. It provides continuous and precise measurements of angular velocity.

In geodesy, large ring laser gyroscopes are used to monitor variations in the Earth’s rotation, including changes in length of day and polar motion. They complement space-geodetic techniques such as VLBI and GNSS by providing independent, high-resolution observations of rotational dynamics, contributing to Earth orientation studies and geophysical research.