[sheepybloke]

This also depends on the plane. For larger commercial applications, you need to have INS. You want to use a combination of sources ideally, since INS is accurate for a shorter period and GNSS/GPS for longer periods(often GPS/GNSS is only updated every second). Plus a lot of newer units have a much smaller drift. This FOG has a drift of 0.1 deg per hour, which is quite good (https://www.advancednavigation.com/solutions/spatial-fog-dua...).