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Minimum Obstacle Clearance Altitude (MOCA)

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Definition

The MOCA is the minimum altitude for a defined segment that provides the required obstacle clearance. A MOCA is determined and published for each segment of the route. (ICAO Doc 8168 PANS-OPS)

Description

The MOCA provides the required clearance above obstacles contained inside the obstacle clearance areas. Charting accuracies are taken into account when establishing minimum altitudes by adding both a vertical and a horizontal tolerance to the depicted objects on the chart.

The minimum obstacle clearance value to be applied in the primary area for the en-route phase of an IFR flight is 1000 ft (300 m). In mountainous areas, the minimum obstacle clearance applied is as follows:

Terrain Elevation Obstacle Clearance
3000 ft - 5000 ft (900 m - 1500 m) 1500 ft (450 m)
Greater than 5000 ft (1500 m) 2000 ft (600 m)

For information concerning the construction of the obstacle segment see ICAO Doc 8168, PANS-OPS, Part I, Section 5.

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