earth science

Tidal atlas

Tidal atlas is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tidal atlas rather than just read about it. In short: A tidal atlas or a tidal stream atlas is used to predict the direction and speed of tidal currents. A tidal atlas usually consists of a set of 12 or 13 diagrams, one for each hour of the tidal cycle, for a coastal region.

Key takeaways

Tidal atlas belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tidal atlas to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tidal atlas from memory before moving on to harder problems.

Reference excerpt

A tidal atlas or a tidal stream atlas is used to predict the direction and speed of tidal currents. A tidal atlas usually consists of a set of 12 or 13 diagrams, one for each hour of the tidal cycle, for a coastal region. Each diagram uses arrows to indicate the direction of the flow at that time. The speed of the flow is shown by the length and thickness of the arrows. For all except the smallest arrows numbers give more precise information. Areas of slack water may be indicated by no arrows or the words "slack water". UK Admiralty Tidal Atlases show speed in units of tenth of a knot. Two figures are given separated by a comma, the first is the mean neap rate and the second the mean spring rate. The dot of the comma indicates where the observations were made. It is important to realise that the tidal hour lasts from half an hour before the nominal time to half an hour after. For instance the chart for 3 hours after high water is valid from HW+2½ to HW+3½, not from HW+3 to HW+4. Tidal atlases may provide additional information for areas such as estuaries where it important to calculate tides away from the ports. Such information may include co-tidal range information and time differences. To calculate the rate at an intermediate tide between neap and spring, interpolation is required. Traditionally this has been done using a "calculation of rates" chart found inside tidal atlases. An alternative to a tidal atlas is a nautical chart that provides tidal diamonds.

References

Citations Cunliffe, Tom (2017). The complete yachtmaster: sailing, seamanship and navigation for the modern yacht skipper. ISBN 978-1-4729-4343-9. Noice, Alison (2015). Yachtmaster for sail & power: a manual for the RYA yachtmaster certificates of competence. ISBN 978-1-4729-2549-7. United Kingdom Hydrographic Office (2015). Admiralty tidal stream atlas: Thames estuary (Edition 2 - 1985 (Reprinted 2015) ed.). Taunton: United Kingdom Hydrographic Office. ISBN 978-0-7077-2123-1.

Worked examples

Example 1 — a first encounter with Tidal atlas

Start with the simplest possible case. Write down what Tidal atlas claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tidal atlas before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tidal atlas ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tidal atlas

In research: Tidal atlas appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tidal atlas in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tidal atlas is common in secondary-school and first-year university syllabi. It links to neighbouring topics Navigation, Oceanography stubs, Tides, so understanding it makes those chapters shorter.
In everyday life: Look for Tidal atlas outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tidal atlas in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tidal atlas means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tidal atlas out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tidal atlas in simple terms?

Why does Tidal atlas matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tidal atlas?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tidal atlas.