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A short class with Sarah and her students. The other ways are under More.
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Today, we're discussing tides. Can anyone tell me the two primary types of tides?
High tide and low tide!
Exactly! High tide is when the water level reaches its maximum, and low tide is the minimum level. Now, what do you think causes a spring tide?
Is it when the moon aligns with the sun?
Good answer! Spring tides occur during new and full moons when the sun and moon align, which enhances gravitational pull. What about neap tides?
They happen during the first and last quarters of the moon?
Exactly! Neap tides result in the lowest high tides. Let’s remember this with the mnemonic 'Noble Neaps – Low Like a Nap.'
I like that!
Great! So, the last major classification includes diurnal and semi-diurnal tides. What do you think the difference is?
Diurnal has one high and one low tide, while semi-diurnal has two of each?
That's correct! Well done! Let's summarize: we covered high and low tides, spring and neap tides, and diurnal versus semi-diurnal tides. Advancing on, we'll see the importance of these in hydrographic surveying.
Now that we understand the types of tides, why do you think tidal measurements are so important in hydrography?
To ensure safe navigation?
Exactly! Tides influence depth readings, so we must apply tide corrections for accurate data collection. Can anyone give me an example of where we might use these measurements?
When charting shipping routes?
Yes, crucial for maritime navigation! When we prepare navigational charts, knowing the tides can prevent accidents. The acronym 'TIDE' could help us remember that! T for 'Timely', I for 'Input adjustments', D for 'Data collection', and E for 'Ensure safety'.
That's a useful acronym!
It is! Remember, tides can significantly change how we interpret hydrographic data. Next, let’s talk about the instruments we use to measure tides.
Finally, let’s explore the types of tide gauges. Who can name a type of tide gauge?
Float-operated gauges!
Correct! Float-operated gauges measure water levels. What else?
Pressure-type gauges?
Indeed! They derive tide levels from water pressure. How about acoustic gauges?
Do they measure the depth with sound waves?
Yes! Acoustic and radar gauges provide highly accurate measurements. We use automatic tide recorders for continuous capture. This seems like a lot, so let’s memorize the gauges with the acronym 'F-PAR': Float, Pressure, Acoustic, Radar.
That’s easy to remember!
Excellent! Remember, technology in measuring tides ensures we gather accurate data for successful hydrographic surveys. Let’s recap: types of tide gauges we discussed include float-operated, pressure-type, acoustic, and automatic tide recorders.
Tides go high, tides go low, spring and neap are the show.
Imagine a moonlit night where the full moon gives a grand rise to the ocean, creating giant waves known as spring tides. But then the moon phases shift, and we see calm waters during neap tides, reminding us of the gentle nature of the sea.
Remember 'SNAPPY' for tides: S for Spring, N for Neap, A for Alignment (sun and moon), P for Peak (high tide), P for Point (low tide), and Y for Year (twice daily for semi-diurnal).
Use 'TIDE' to remember: T for Tidal correction, I for Input adjustments, D for Data collection, E for Ensuring safety.
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What are spring tides?
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Why are tidal corrections necessary?
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What characterizes a semi-diurnal tide?
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How do acoustic tide gauges function?
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The maximum water level observed during the tidal cycle.
The minimum water level observed during the tidal cycle.
Higher than normal tides occurring during new and full moons due to gravitational alignment.
Lower than normal tides occurring during the first and last quarters of the moon.
Tides occurring once each lunar day, with one high and one low tide.
Tides occurring twice each lunar day, with two high and two low tides.
An instrument used to measure tidal levels in oceans, seas, or other water bodies.
This section discusses the various types of tides and their measurement techniques, including the importance of tide corrections in hydrographic surveying.
In this section, we explore the different types of tides, including high and low tides, spring and neap tides, as well as diurnal and semi-diurnal tides. We also delve into the significance of tidal measurements in hydrographic surveys and introduce various types of tide gauges used to collect data accurately.
Hydrographic surveying heavily relies on tidal measurements, which are classified into several types:
Tide levels play a critical role in hydrographic surveying as they affect depth readings. Accurate tide corrections are essential during data collection to ensure precise mapping and navigation safety.
Several types of tide gauges are utilized to monitor tide levels: