Maritime adopted its own system for measuring distances and speeds. Units of measurement may be obscure for people who are not related to the sea, so determining the distances and speed of movement of ships can present some difficulties. The main unit of speed used at sea is the sea knot. What it is equal to and how to calculate the speed with its help will be considered in the article.
Nautical mile
At sea, the main measure of distance is the mile. It is important to note that a sea mile and a land mile are two different things. The land is 1609 meters. The nautical mile is equal to the length of one minute of the line of the earth meridian. The Earth’s meridian is conventionally an arc, and its length is measured in degrees, minutes and seconds. Thus, the length of one nautical mile is 1852 meters. The difference between the land and nautical miles is significant, so it’s important not to confuse these units.
In addition to miles, distance to the sea is measured using units such as feet, inches, yards, fathoms and marine cables.
Nautical knot: ship speed
Having dealt with the distance to the sea, you need to turn to the concept of speed. To determine the speed at sea, the concept of a node is used. A knot is a unit of speed at which a ship travels one nautical mile in an hour. How many km are in the sea node? It turns out that one maritime knot is 1.852 km per hour. Thus, 10 nautical knots is 18.5 km per hour, 100 nautical knots is 185 km per hour and so on.
Ship Speed Calculation Example
The ship moves at a speed of 20 nautical knots. He needs to walk a distance of 100 km to his destination. What is its speed in kilometers, and how long will it take him to cover a given distance?
First you need to translate the speed from knots to kilometers, for this 20 need to be multiplied by 1.852. It turns out that the speed of the ship in kilometers is 37 km per hour.
Then you should divide the distance of 100 km by ship speed of 37 km / h. It turns out that the ship will need about 2.7 hours to reach its destination, traveling at a speed of 20 nautical knots.
Ship speeds depend on their size, technical characteristics, purpose and other factors. Cargo ships and passenger liners usually run at a speed of 10-20 knots, and military ships are capable of developing much higher rates of movement. For example, the HCMS Bras D'Or 400 warship has a speed of 62 knots (116 km per hour).
The origin of the term "maritime knot"
Shipping is one of the oldest human activities. It is obvious that in ancient times there were no compasses, locators, navigators and other technical achievements of late times. However, the sailors needed to look for some landmarks in order to determine their location. They were guided by the stars, the moon, lighthouses, the outlines of the coastal relief, and so on.
To determine the distance traveled, a particular invention was used. It was called lag and was a log with a rope tied to it. Knots were tied on a rope at an equal distance from each other. The lag was thrown from the stern of the ship. When the rope was pulled, the sailor counted the number of knots passed during the movement of the ship through his hands.
And the tradition of measuring speed by sea knots has entrenched, although the modern knot has a different value than in ancient times. In modern navigation, the lag is still used to measure the speed of the ship. It looks, of course, different than in the past, and is a special device.
So, at sea, the calculation of speed in marine nodes has been carried out since ancient times. The node corresponds to the speed at which the ship will go one nautical mile per hour. To convert the speed in knots to the speed in kilometers, you need to multiply the knots by 1,852 (the length of one nautical mile).