They do, but compounding errors are always a problem with inertial navigation.
Instead of GPS, they can use fixed radio beacons like VOR and TACAN (which I think are both just US systems, but there are similar systems around the world and at major airports). This is basically the system that was in use before GPS.
EDIT: grammar
You can do this in VLC, though it’s not very practical. VLC’s equalizer has a preamp slider, it’s just not great if you want to change it all the time.