a) over high terrain or in mountainous areas, at a level which is at least 600 m (2 000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft;
a) over high terrain or in mountainous areas, at a levelwhich is at least 600 m (2 000 ft) above the highestobstacle located within 8 km of the estimated position of the aircraft;