What is measured to ensure navigation reception along the entire route when using MEA?

To ensure navigation reception along an entire route with respect to Minimum Enroute Altitude (MEA), the primary focus is on altitude and obstacle clearance. MEA is determined by ensuring that there is a safe altitude above the highest obstacles along the route while also providing adequate signal reception from navigational aids.

Maintaining the correct altitude is vital for ensuring that an aircraft remains clear of terrain and obstructions, which is a critical safety consideration. Additionally, MEA guarantees that the aircraft will have reliable navigational signal coverage. This combination of altitude maintenance and obstacle clearance helps to prevent collisions and allows for a successful navigation experience.

The other options, while relevant to flight planning and safety, do not directly address the specific measurements associated with ensuring navigation reception along the MEA. For example, visibility requirements pertain more to visual flight rules and landing rather than enroute navigation. Similarly, while understanding the time required for approach is important for scheduling and managing flight paths, it does not influence the navigation reception related to MEA. Weather conditions can affect overall flying safety and navigation, but they do not specifically ensure navigation reception along the MEA itself. Hence, altitude and obstacle clearance stands out as the key measurement in this context.