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What is a Tide Chart?

Tide charts may outline expected times for high and low tides in a given day.
Tides generally are less noticeable in the open ocean than along the shoreline.
The Moon's gravitational influence on the oceans of the Earth helps create the tides.
The captains of tugboats that assist larger ships in harbors must be aware of how the tide affects water depth changes.
A tide chart often includes the times of sunrise and sunset.
The captain of a container ship must pay careful attention to tidal data when offloading cargo from his vessel.
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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 13 December 2014
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Tides are defined as the regular rise and fall of ocean water above or below mean sea level. Depending on where a person is on Earth, and the position of the Earth, moon, and sun relative to each other, tides will vary. For this reason, most parts of the world publish tide charts, in the form of a small table which outlines the expected times for high and low tide through the day. Usually, a tide chart includes the estimated height of each tide, along with the times of sunrise and sunset, along with moonrise and moonset. By using the data in a tide chart, people who work with the ocean can have safer and more productive days.

A proper tide chart is a vital navigational aid, especially when maneuvering large ships close to shore or into harbor. A miscalculation in the tides could result in a catastrophic accident such as a collision with a bridge or running aground. Sailors making day trips, such as fishermen who go out every day, have tide charts relevant to their local area to assist them in deciding when to go out and where to travel. Larger ships traveling around the world often take advantage of computerized tide charts, which can display data for any location in the world.

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Tides are caused by the gravitational pull of the moon and sun on the water which covers the Earth. Because the positions of all three bodies can be easily projected, scientists can predict the tidal patterns for an area and create a tide chart. A tide chart also takes the topography and history of the region into account, and is a very specific document designed to be used in a small area. Generally, there are four tides a day: two high tides, and two low tides. The variation in height between the tides depends on location, season, and astronomical phenomena; sometimes the variation is only a few feet, while on other occasions it has been recorded to be as much as 50 feet (15 meters). In most cases, a tide chart will also include a graph to help readers visualize the differences between the tides.

Usually, a tide chart will be published for a general region with a list of corrections for specific areas in the front. For example, you may need to add or subtract minutes to the time to get an accurate estimate of when a high or low tide is going occur. In addition, there may be variances in height, which are also listed in the regional corrections. When reading a tide chart for a region, first check to see if you need to make corrections, and then open it to the relevant day. Make any adjustments needed for an accurate reading, and plan your day accordingly.

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Fiorite
Post 3

Reading tide charts can be useful to surfers. Knowing the tide patterns for your spot, will help you know what times are the best to catch the surf you like. Surf picks up as the tide goes out, so usually a few hours before low tide is the best surf.

Ultimately, the best surf depends on the topography of the spot, but as a general rule of thumb, tides moving out are best catching rideable waves (unless you longboard). This is because shallow water makes swells bigger, so if big swells are rolling in, surf will be the biggest at low tide. You just have to make sure there is enough water to ride the wave out. If the water is too shallow, the wave will break straight down the face into the shore or rocks below.

istria
Post 2

@ Chelclock- High tides occur at a relatively constant 12 hour and 25 minute interval. The low tide occurs halfway between high tide periods. This is the same for all of the earth's oceans. The variance in the tides relate to amplitude. Changes in amplitude depend on the location of the moon and the sun relative to the area the tide chart has been mapped for as well as the geographical features of the shoreline.

Remember though, just because the interval between tides is the same, that does not mean the tides happen at the same time across the globe. Washington State's Whidbey Island tide chart will have different high and low tide times than Hawaii's Big Island Tide chart.

chelclock
Post 1

What is the normal time between tides on the east coast of America?

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