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HomeShips & VesselsHow Fast can Ships go? Knots Explained

How Fast can Ships go? Knots Explained

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One of the frequently asked questions to me is how fast are the ships?, ship speed, what is the ship speed ? I wanted to write an article on how fast do ships go to answer questions such as: Of course, before that, I will try to explain the subject by talking about some maritime terms that we need to know about ship speed.

Ship Speed ​​Measurement Unit Knots

You may have heard the word knot when talking about the unit of speed, especially in maritime and aviation. The expression km/h on land is expressed in knots in maritime and aviation.

The word “knot” means the path recorded in 1 hour. If it will be used for a ship, 1 nautical mile in 1 hour is equal to 1 air mile recorded in 1 hour if it will be used in the aviation industry. From here, we understand that nautical miles and air miles are different things.

  • 1 nautical mile is 1852 meters.

Ship Speed ​​Measuring Device

So, how is ship speed measured? question comes to mind. Undoubtedly, people used certain instruments and a device to measure ship speed for this purpose. Let’s take a look at its historical development first.

It is known that sailors have been trying to find the speed of the ship with an instrument called a longline to measure the speed of the ships since the 1600s . This system consisted of a triangular piece of wood tied to the end of a rope and an hourglass. There were knots, or “knots”, tied at equal intervals (approximately 14.4 meters) on the rope. While the ship was cruising, that is, on the water, the piece of wood at the end of the rope was thrown into the water from the back of the ship and the knots on the part of the rope above the sea were counted in a certain time interval (about 30 seconds) measured by the hourglass. For example, if 10 knots were counted in 30 seconds, the speed of the ship would be expressed as 10 knots. 1 knot measured by this method was approximately equal to 1 nautical mile in 1 hour.


Ship Speed ​​Measurement with Chip Log Method

It would not be possible without mentioning the chip log method on ship speed measurement methods . It should also be noted that the chip log method, which is known to have been actively found and used in the 1500s-1600s, and all previous methods were used by Dutch sailors.


The Chip Log ship speed measuring instrument consisted of a thin rope wound on a reel and a plate with weight holes at the end of this rope. Knots were tied at certain equal intervals on the rope between the wooden plate and the pulley. It was based on the method of assuming the speed of the ship as 1 knot, through the hourglass, at each point where these nodes touched the water. How to measure ship speed with chip log? Watch the video below and you can have information about it.

How Is Ship Speed ​​Measuring Today?

Today , different methods are used for ship speed measurement. One of them is the sonar systems we call Speed ​​Log. The system, which is positioned at a certain point of the ship, can determine the speed by making the ratio between the return time and the progress amount of the ship by spreading certain waves to the sea.

Another frequently used method is through GPS, global positioning services, whose history does not go back that far. In fact, speed detection with GPS can be used not only for sea vehicles, but also for speed detection of almost all moving vehicles.

Measuring boat speed with actual knots (a chip log)


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