how is the height of an ocean wave measured

Since at least the 1920s, there has been a considerable debate about how is the height of an ocean wave measured?

Some researchers use mathematical calculations of the wavelength—the distance from one crest to the next.

Others make measurements using an oscillation meter device mounted on a boat during an expedition.

The tallest point of a wave is measured from the point where the wave swell meets the water surface to the topmost point of the ocean wave, usually called the crest.

This is because this data can help predict erosion and other phenomena related to other wave phenomena.

A Glossary of Ocean Wave Terms

ocean wave terms

Trough

The trough of a wave is the lowest point, or lowest part, of a wave cycle.

Near land, in exceptionally shallow water near the beach, wave troughs can be deep and wide.

In fact, they may be so deep that they can be dangerous for swimmers and surfers.

Peak

When ocean water builds up along the shore to form a wave, it becomes rough.

As the swell approaches land, it gets higher and then pushes against the bottom to a maximum achievable height.

This is called the ocean wave peak. The highest ocean wave peaks are usually found away from the ocean shore.

Crest

crest waves

A crest is the highest point on a wave, the point where it rises the most before it falls.

Crests occur when a wave moves away from its starting position and returns to that same place at a later time. Then, the cycle of the wave is complete.

Horizon

It’s the furthest point where an observer can look into the ocean. The horizon is relative to wave height.

On a calm day, the wavelength can be seen for about 20 miles.

Rainy or cloudy weather will limit the wavelength an observer can see for the height measurement of an ocean wave.

Back-Rush Curl

Whenever there are rising or falling tides the seawater rushes up the beach, resulting in a back-rush curl or wave that outwardly ripples.

The curls can be used to make an estimate of sea levels.

As waves approach shallow water, the troughs of the waves assume different characteristics.

A trough develops due to many subtle factors, and can vary greatly from one wave to the next.

How to Measure Ocean Wave Height

measure ocean wave

In the next section, we’ll go into the details of how is the height of an ocean wave measured and review several standard methods for measuring ocean wave height.

It isn’t easy to accurately measure wave height and period manually. Here are several examples of ocean wave measuring methods:

Height of Eye and Ocean Wave Height

While you are in a boat on even seas, any wave that obscures your view of the horizon is higher than an average person would typically hold their head.

You can use other elements of the boat to make this height estimation (such as the deck edge, railings, etc.).

The easiest way to measure water surface height or wave height is by using two different points of view:

  • One from above on a cliff or other high place and
  • The other from below in a deep trough.
Note: It's worth noting that using this method to determine the ocean wave height still requires your keenness to get accurate results

Depth Sounder and Ocean Wave Height

depth sounder and ocean wave

Using a digital depth finder’s with reliable update speed is the best instrument for measuring ocean wave height.

Depth measurement of ocean wave trough at the crest, compared to the same point on an adjacent wave, will give you accurate wave height results.

Floating Vessel and Ocean Wave Height

This method can be used when a vessel is ashore, when the weather conditions are good and the boat isn’t moving too fast.

To determine the height of waves, take the boat’s length and add it to the total distance between the waterline and the top of the buoy.

If you know this, you can make a rough estimation of the height of the ocean waves.

Watch waves cresting around a vessel to determine the size of the hull exposed above water.

You can predict the size of the next wave before it breaks.

This is the method used by ship captains to know whether there are heavy storms, waves, or obstacles ahead when at sea.

Surfer’s Height

the surfer's height

When measured in this way, wave height depends on the skier’s height compared to others, how large they appear in a video or photo, or the viewer’s estimation of the rider’s size.

To determine the height of waves using a surfer’s size, one should view the wave face from a directly vertical positioning.

When looking at waves from above, the estimated wave height is greater than the actual wave height.

And when looking up at waves, the estimated wave height is less than the fundamental wave height.

Fixed Structures and Ocean Wave Height

This method is called screening.

Making observations at a break-wall, pier, or jetty can provide accurate wave data.

The presence of this structure can also be used to measure the period of the waves.

Note: When waves break over a structure before reaching the shore, the distance between two crests can be measured and used to calculate the wave period.

Scale and Ocean Wave Heights

scale and wave height

As a method on how do you measure ocean wave height scale method is measured in relation to the rider or scientist, who stands on a flat platform to perform the measurement?

The measurement is relative to feet and inches. This method has been used since the early 1900s.

It is also worth noting that the unit when measuring ocean wave height should be one that is reasonably accurate.

Even though there is currently no international standard for measuring ocean wave height scientists from most countries worldwide report wave heights in meters.

Wave Buoys

a wave buoys

Using wave buoys is one of the most common methods on how to measure sea wave height.

They are capable of measuring sea waves to give forecasters a more accurate picture of ocean weather patterns.

This can result in more effective warnings to shipping and a reduction in damage to coastal land.

If the bottom contour or depth of the water changes sharply, the size of an ocean wave is affected, and the height and duration of waves that break there will be different.

This is especially true if waves are breaking in shallow water.

Fact: Ocean and sea waves breaking in deeper waters tend to be larger than those breaking in shallower waters.

Hawaiian Method

the hawaiian method

During the 1960s, some surfers came into favor of using wave buoys as a means of measurement.

At the same time, other surfers felt that these new wave buoys were inaccurate due to an increase in “Hawaiian” wave reading and not actual wave height.

Hawaiians were the first to estimate ocean wave size by counting peaks from a surfer’s vantage point.

The Hawaiian method on how to measure sea wave height has since been adopted globally by scientists and recreational surfers alike.

However, inaccurate estimations can result from this method because of the difference between face size and back size.

Read Next: How Do Mountains Affect Weather?

Final Thought

So how is the height of an ocean wave measured by experienced surfers and scientists?

Experienced surfers, they might use a combination of eye tests and physical measurements to determine estimated wave height.

When measuring wave height, several different approaches surfers, sea crews, and scientists have developed over time to determine wave height.

For instance, inexperienced surfers might measure the distance from the crest of one wave to the next instead of the distance from trough to peak.

Scientists observing waves might use tools such as sonar or satellite images as well as a process called GPS tracking.

The different methods mentioned are helpful, but they require experience and practice.

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