The prevailing visibility is determined from which observation point?

The prevailing visibility is primarily determined from ground level. This is because visibility is assessed based on the distance at which an observer can clearly see prominent objects. Weather conditions on the ground, such as fog, rain, or snow, directly influence how far one can see, making ground level the most relevant observation point for determining prevailing visibility.

Weather stations indeed gather a variety of meteorological data, but that data is often synthesized with ground-level observations to provide a broader understanding of visibility conditions in the area. Observations from aircraft altitude do not account for the visibility that ground-based personnel or vehicles experience, as visibility can vary greatly between ground level and the air. Similarly, cloud base information is related to vertical visibility and does not directly translate into horizontal visibility, which is what prevailing visibility refers to.