What is the purpose of MOCA in IFR operations?

The purpose of Minimum Obstruction Clearance Altitude (MOCA) in Instrument Flight Rules (IFR) operations is to ensure safe terrain clearance between specified fixes. MOCA is the lowest altitude that provides acceptable navigational signal coverage, which is important for maintaining a safe distance from obstacles such as mountains, buildings, and other obstructions.

When flying at or above MOCA, pilots can be assured that they are maintaining a safe vertical separation from the terrain along the route they are navigating, thus reducing the risk of controlled flight into terrain (CFIT). MOCA is particularly relevant when navigating in mountainous areas or regions with significant elevation changes. This altitude is defined for specific segments of the IFR airway system and is crucial for pilots to know, as it aids in maintaining safety while relying on navigation aids for guidance.

The other options do not fulfill the specific function of MOCA. For instance, visual navigational guidance is more relevant to VFR operations where pilots fly with visual references rather than relying solely on instruments. The mention of alternate landings relates to the availability of airports and is addressed through different regulations and altitudes. Measuring distances between navigation aids is not the primary concern of MOCA, as it focuses more on ensuring safe vertical separation.