About: Minimum obstacle clearance altitude

Minimum Obstacle Clearance Altitude, or MOCA, is the lowest published altitude in effect between fixes on VOR airways or route segments that meets obstacle (like a building or a tower) clearance requirements for the entire route segment. Within the United States, this altitude also assures acceptable navigational signal coverage only within 22 nm of a VOR. The MOCA seen on the en route chart, may have been computed by adding the required obstacle clearance (ROC) to the controlling obstacle in the primary area or computed by using a TERPS chart if the controlling obstacle is located in the secondary area. This figure is then rounded to the nearest 100 foot increment, i.e. 2,049 feet becomes 2,000, and 2,050 feet becomes 2,100 feet. An extra 2,000 feet is added in mountainous areas, 1,000 i