https://en.wikipedia.org/wiki/Inertial_navigation_system#Drift_rate https://en.wikipedia.org/wiki/Inertial_navigation_system#Dri... not that great although they

https://en.wikipedia.org/wiki/Inertial_navigation_system#Drift_rate https://en.wikipedia.org/wiki/Inertial_navigation_system#Dri... not that great although they've been in use for many decades.