There is nothing quite like looking out at the vastness of endless blue water. This type of view is genuinely captivating and never really gets old. While the sight of open seas and oceans is incredible, it can get a bit confusing when you get into the measurements used to describe these immense, featureless distances. 

It may surprise you that the measurement used to gauge and describe distance on open water differs from what is typically used to measure distance on land. To help you understand these measurement units, we will explain the differences between statute and nautical miles. 

By understanding the primary measurement seafarers use, you can get into the mindset of a true maritime explorer and take your cruise experience to the next level.

A nautical mile is a measurement unit used to describe distances on open bodies of water, like oceans and seas. Unlike statute miles, which you may simply know as miles, nautical miles consider the degree of the Earth’s curvature. As such, a nautical mile is actually slightly longer than the statute miles we use to measure a land mile. 

A nautical mile would equal 1.1508 statute miles or 1852 meters when measured on land. This may initially sound slightly confusing, but it is because a nautical mile is based on the Earth’s longitude and latitude. In fact, a nautical mile is equal to exactly one minute of latitude. 

Since vast bodies of water, like oceans and seas, actually curve with the planet’s surface, it is necessary to consider this curvature when measuring distances across the water accurately. 

As mentioned above, you are probably far more familiar with statute miles than nautical miles. A statute mile measures 5280 feet, or 1609.3 meters, if you use the metric system. In the United States, miles are used as one of the primary measures of distance, especially on roads. 

Now that you understand the differences between the two measurements, we can explain why nautical miles are relevant for cruise ships. Whether you are just curious or would like to follow an upcoming cruise vacation’s itinerary accurately, the following information will be useful to you. 

Route Planning and Itinerary Details

When you view the itinerary for your cruise vacation, you may notice that the route is measured in nautical miles. More specifically, the distances between various ports of call, regions, and sights might be noted in nautical miles. Sometimes, you may see nautical miles abbreviated as “NM” or “nmi” on travel itineraries and documents.

Ship Route Planning (Photo Credit: Maksim Shmeljov)

Nautical miles are much more precise distance measurement over the water and are used for navigational calculations. Since the cruise ship’s navigation team uses nautical miles to plan and chart the ship’s route, they often provide passengers with this information on any nautical chart or navigational map they distribute.

Read Also: What is the Steering Wheel on a Ship?

This gives passengers a more accurate picture of where their vacation will take them and adds to the sense of maritime adventure. Knowing that you will travel across hundreds to thousands of nautical miles can help you feel like you are exploring and traversing the open seas. 

You may also notice that nautical miles are used in measuring the cruise ship’s speeds throughout your voyage. Just like miles per hour are used when traveling via automobile, train, or plane, nautical miles per hour are used to measure the speeds of cruise ships and other seafaring vessels.

Bridge of a Cruise Ship (Photo Credit: ODIN Daniel)

Rather than nautical miles per hour, you may notice that the speed is measured in knots. This is the unit of speed used to describe nautical miles per hour. So, in statute miles, one knot would be equivalent to 1.151 miles per hour on land.

While nautical miles are the primary nautical unit of measurement for distance while the ship is on the water, statute miles can be used in some capacity during your cruise vacation. 

For starters, statute miles can be used to measure the distance to various excursions on shore. If your trip involves stopping at multiple ports of call, you may see miles and kilometers used to describe the distance to various land-based destinations.

Many wonder why maritime navigation uses knots to measure distance rather than saying nautical miles per hour or NM/hr. Like most maritime terminology, the term knot has a long-standing historical meaning. 

In the past, sailors would tie a buoyant object to a line with obvious knots connected to it at exact measurements. This object would be dragged behind the boat, and the line would be let out. The sailors could then count the number of knots that slipped through their hands over time to understand the ship’s speed. 

Degrees of latitude are divided into 60 minutes. Each minute is then divided into 60 seconds. The purpose is to allow for precise measurements of distance. One minute of latitude equals 1.15 statute miles or 1.8 kilometers. 

For most cruise ships, the average top speed is about 20 nautical miles per hour or 20 knots. The larger cruise ships can travel at slightly faster speeds. According to Royal Caribbean, the average speed for their cruise ships is about 18 to 20 knots.

While the difference between nautical and statute miles may seem insignificant, it is important when navigating open water. Understanding the difference and being able to participate in conversations about nautical miles and knots can add to your overall cruise experience. 

Why not fully embrace the experience of being out on the water by including this terminology in your onboard conversations? The next time you are on the water, take in the views and embrace all of the maritime terminology. Trust us; it’s really fun!

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