1. Significant Wave Height (Hs): This is the most commonly used measurement. It's calculated as the average height of the highest one-third of the waves during a specific time period, usually 20 minutes. This gives a more representative value of the overall wave activity.

2. Individual Wave Height (Hi): This refers to the height of a single wave, measured from the trough (lowest point) to the crest (highest point). This method is less common because it only captures the height of one particular wave, which might not reflect the overall wave conditions.

Here's a breakdown of how the measurements are taken:

* Buoys: These are floating devices anchored to the seafloor. They have sensors that measure the vertical motion of the water, which is used to calculate wave height.

* Radar: Some coastal radar systems can measure wave height by analyzing the reflection of radar waves off the ocean surface.

* Satellite imagery: Satellites can also measure wave height using radar or optical sensors.

* Visual observation: This is the least accurate method. Trained observers visually estimate the wave height using a scale or a dedicated instrument like a wave staff.

Factors affecting wave height:

* Wind speed and duration: Stronger winds and longer wind duration create larger waves.

* Fetch: The distance over which the wind blows across the water. Longer fetches produce higher waves.

* Water depth: Waves become steeper and break when they approach shallower water.

It's important to note that wave height is just one parameter used to describe wave conditions. Other important measurements include wave period (time between wave crests) and wave direction.

Overall, the specific method used to measure wave height will depend on the context and purpose of the measurement.