FAA Weather Observation Practice Exam - Prep, Practice Test & Study Guide

When determining the prevailing visibility, the horizon circle can be divided into eight sectors. This division into eight sectors allows for a more detailed assessment of visibility in various directions around the observation point.

The idea behind this segmentation is to ensure an accurate representation of visibility conditions as they can vary significantly from one direction to another. Observers will assess the visibility in each of these sectors, typically using visual references or other measurement tools, and then determine which sector has the best visibility, often influenced by obstacles or atmospheric conditions such as fog, precipitation, or haze.

Once this assessment is made, the prevailing visibility is often taken as the most common visibility observed in these sectors. This method is particularly important in aviation, where clear and accurate visibility information is crucial for safe operations.