Terms to Know for Your Captain’s License

Source: Mariners Learning System, By Captain Bob Figular

Travel in the water is not the same as it is on the road. For example, you don’t have potholes or bumper- to-bumper traffic in the open water. The terms are not the same either. If you’re going for your captain’s license, you will probably know what a knot and nautical mile are, but it’s still important to review and know the history behind the terms to have a more complete understanding of navigating the waters.

A nautical mile is defined as the unit of length that is about one minute of arc of latitude along any meridian. The agreed upon length of a nautical mile is 1852 meters or 6076 feet. This differs from a terrestrial mile, which is 5280 feet. The defined nautical mile is accepted by both the International Hydrographic Organization and the International Bureau of Weights and Measures.

The nautical mile was defined in Monaco at the First International Extraordinary Hydrographic Organization in 1929. The move was an attempt to have a uniform definition as countries had definitions of their own. The nautical mile is used by a variety of people, departments, businesses and organizations, including those concerned with navigation, exploration, and diplomacy. This is due in part on how well the nautical mile lends itself to nautical charts. It is easy to measure nautical miles, which helps in navigation.

A knot is the unit of speed equal to one nautical mile per hour. Therefore, if you’re going ten knots an hour, you will have traveled ten nautical miles in one hour or just a little oven eleven terrestrial miles. The knot is used in many different industries including meteorology for checking storms and patterns and navigation through the air and water.

The term is derived from the old chip log measuring system. Up until the 1800s, the speed of ships was measured using a chip log. Knots would be placed along a line at roughly 47 feet, and as they passed through a sailor’s hands, they would be counted and timed with a 28 second hourglass. If you are going for your captain’s license, you should know these terms and others. Learn more about Mariners Learning System today.