The average accuracy is approximately 5°, which consists of:
- site error (terrain and other obstacles) - up to 1°
- propagation error (signal travel) - up to 1°
- airborne equipment error - up to 3°
The maximum internal error of VOR is 1° and is measured by a monitor in vicinity of the VOR, which puts VOR into standby mode if:
- bearing mesured changes by more than 1°
- the drop in signal strength is more than 15%
- the monitor fails (altough the VOR may remain functional provided the NOTAM is issued stating the VOR isn't monitored and should be used with caution)