If a light's range on a chart is listed as 12 miles, which unit is this measurement in?

If a light's range on a chart is listed as 12 miles, which unit is this measurement in?

• A. Statute miles
• B. Nautical miles
• C. Kilometers
• D. Meters

Answer: (A)

Statute miles are the unit used for light ranges on many charts. Light range tells you how far the light is visible under normal conditions, not how far a vessel travels. Nautical miles are used for ship motion and navigation distances, so a light’s range is typically given in statute miles. So a listed range of 12 miles means 12 statute miles (about 10.4 nautical miles). Kilometers or meters would indicate metric charting, which isn’t the convention here.

Statute miles are the unit used for light ranges on many charts. Light range tells you how far the light is visible under normal conditions, not how far a vessel travels. Nautical miles are used for ship motion and navigation distances, so a light’s range is typically given in statute miles.

So a listed range of 12 miles means 12 statute miles (about 10.4 nautical miles). Kilometers or meters would indicate metric charting, which isn’t the convention here.