Can someone explain me the difference between minimum obstacle clearance altitude and obstacle clearance altitude? I read definitions in Doc 8168 but i don't really see the difference. I would be grateful if someone explain where which type of altitude is used.
From ICAO Doc 8168:
Minimum obstacle clearance altitude (MOCA). The minimum altitude for a defined segment that provides the required obstacle clearance.
Obstacle clearance altitude (OCA) or obstacle clearance height (OCH). The lowest altitude or the lowest height above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria.