What visibility measurement is typically used to report fog conditions?

Visibility measurements for reporting fog conditions are typically reported in statute miles. This unit is commonly used in aviation and meteorological contexts to describe how far one can see horizontally. In the case of fog, visibility may be significantly reduced, often leading to reports of visibility less than a specific threshold, thereby informing pilots and air traffic controllers about potentially hazardous flying conditions.

Statute miles provide a familiar reference for pilots who operate within the United States and in many other countries, making it easier to relate visibility to operational parameters such as minimum required visibility for takeoff and landing.

Other units of measurement, such as knots, yards, and kilometers, do not serve this specific purpose as directly as statute miles. Knots are a measurement of speed, used primarily in aviation and maritime contexts; yards are less commonly utilized in aviation and are not standard for visibility reporting; while kilometers, although used in many parts of the world, are not the standard in the U.S. aviation context, where statute miles dominate.