WEEK 16 & 17 TOPIC 2 PUBLICATION FOR PREDICTING TIDES AND CURRENTS.pptx
1. WEEK 16 & 17
TOPIC 2: PUBLICATION FOR PREDICTING TIDES AND
CURRENTS
LEARNING OUTCOMES: At the end of the session, the students should be able to:
1. Determine the use of publications for predicting tides and currents
- Tide tables
- Tide Predictions for Reference and Subordinate Stations
- Tide Current Charts and Tables
- Current Diagrams
- Reed’s Nautical Almanac
- McMillan’s Nautical Almanac
- Computer Predictions
2. TIDE TABLES
A tide table is an assortment of data compiled about the tide
levels at different times, which would enable the captain of a
vessel to adjust the docking time of the ship or the boat
accordingly.
3. TIDE PREDICTIONS FOR REFERENCE AND
SUBORDINATE STATIONS
Tide predictions for subordinate stations are generated by first
generating high/low tide predictions for a designated harmonic station,
called the “reference station”; then time and height adjustments are applied
to correct the high/low predictions to the tidal conditions at the subordinate
station.
4. Subordinate stations are historic stations which do not have tidal
harmonic constants available. Tide predictions for subordinate
stations are generated by first generating high/low tide predictions
for a designated harmonic station, called the “reference station”;
then time and height adjustments are applied to correct the
high/low predictions to the tidal conditions at the subordinate
station. Subordinate stations only allow for the generation of
high/low tide predictions, and heights will be relative to Mean Lower
Low Water (MLLW), the standard chart datum for the U.S. coastline.
5. Tides and Tide Prediction
Halls Harbour, Nova Scotia; and Halls Harbour, six hours later.
from Greenberg, p.128A
6. * General stuff about tides and tide prediction (this page).
* Samples of today's tide predictions from the National Ocean Service and from the
WWW Tide and Current Predictor.
* About Water Levels, Tides and Currents (includes some history of tide prediction) from
the NOAA/NOS website.
* Tide Spectra and Tide Sounds: The predicted tidal record for various ports interpreted as
musical scores.
* The Song of the Tides: 3000 hours from Ancona and Venice, arranged for woodwinds,
marimba by Levy Lorenzo.
* More detailed information about Harmonic Analysis of Tides.
* A nice Calculus with Calculators exercise: The Priming/Lagging of the Tides.
* References.
NOTE: Some of this information appears in a 3-part column I wrote in April-June 2001 for "What's New in
Mathematics" on the American Mathematical Society webpage. Part III of the column has a lovely JAVA animation
of a tide predictor, due to Bill Casselman.
Tides and history: The tide predictions for D-Day by Bruce Parker, in Physics Today.
7. TIDE PREDICTION. People going into or out of a
harbor, or anchoring near a shore, need to know in
advance about the behavior of the tide. The tide is
caused by the pull of the sun and the moon on the
oceans, and the rotation of the earth, but its exact
pattern at any particular spot on the coast depends
very strongly on the shape of the coastline and on the
profile of the sea floor nearby. So even though the
forces that move the tide are completely understood,
the tides at any one spot are essentially impossible to
calculate theoretically. What we can do is to record the
height of the tide at that spot over a certain period of
time, and use these measurements to predict the tides
in the future. Here is a typical tide record: this graph
shows the height of the water over fourteen days.
8. This figure shows the tidal record for two weeks (January 1-14, 1884)
at Bombay. The tide was recorded on a cylindrical sheet that turned once
every 24 hours. Each daily curve is labelled with its date. Some obvious
features: there are usually two high tides and two low tides each day; the
tides come about 50 minutes later each day; during the two-week period
there is considerable variation in the daily pattern of highs and lows;
there is usually a difference in height between two consecutive high tides
(the diurnal inequality). [From G. H. Darwin's Encyclopaedia Britannica
article, now available online. Note that in this graph, time increases to
the left.] Larger image.
9. Times of high tides are computed
and published by the National Ocean
Service. For a current sample,
click here. For a complete analysis of
one location (Port Aransas, Texas) with
an interesting tidal pattern, click here.
The method used today in the United
States is a modification of the method
called ``harmonic analysis.'' In fact, until
1965 tide predictions were generated
by machines along the lines of this one
10. TIDAL CURRENT CHARTS AND TABLES
What is tidal current charts and tables?
NOAA's Tide Tables and Tidal Current tables are used by mariners for
navigation. They contain tide and/or tidal current predictions and
associated information produced by and obtained from the Department of
Commerce, National Oceanic and Atmospheric Administration, National
Ocean Service.
11. Using Tide Tables
Tide tables are produced by Fisheries and
Oceans Canada and are available online
or in print form. They are split into seven
different volumes for the different regions
of Canadian waters. Find the volume that
applies to the area you will be sailing in.
Tides for the Strait of Georgia are in
Volume 5. Within this volume, you will
find the annual tides for each tide station.
Let’s look at an example tide table for
Gibsons on the Sunshine Coast.
12. How to Read a Tide Table
1.Step 1: Look Up Daily Tide Information for Your Location.
There are different ways to get information about
daily tides for your particular area or location. ...
2.Step 2: Look Up the Dates You'll Be Out. ...
3.Step 3: Make a Note of the Times of High and Low Tides.
13. CURRENT DIAGRAMS
What is ocean current explain with diagram?
Ocean currents are the continuous, predictable, directional movement of seawater
driven by gravity, wind (Coriolis Effect), and water density. Ocean water moves in two
directions: horizontally and vertically. Horizontal movements are referred to as currents,
while vertical changes are called upwellings or downwellings.
14. REED’S NAUTICAL ALMANAC
Reeds Nautical Almanac is the indispensable
trusted annual compendium of navigational
data for yachtsmen and motorboaters, and
provides all the information required to
navigate Atlantic coastal waters around the
whole of the UK, Ireland, Channel Islands and
the entire European coastline from the tip of
Denmark right ...
15. McMillan’s Nautical Almanac
McMillan's agricultural and nautical almanac for 1888 : with astronomical
tables adapted to the provinces of New Brunswick and Prince Edward Island
1888 ..
16. COMPUTER PREDICTIONS
A tide-predicting machine was a special-purpose mechanical analog computer of the
late 19th and early 20th centuries, constructed and set up to predict the ebb and
flow of sea tides and the irregular variations in their heights – which change in
mixtures of rhythms, that never repeat themselves exactly.
Tide Predicting Machines
are analogue computers which
simulate the rise and fall of the
ocean tide. These machines
were built during the period
1872 to 1964. ...
17. …machines, as for example the tide predictor developed in 1873 by William Thomson
(later known as Lord Kelvin). Along the same lines, A.A. Michelson and S.W. Stratton built
in 1898 a harmonic analyzer (q.v.) having 80 components. Each of these was capable of generating a sinusoidal
motion, which could be…
18. WEEK 16 & 17 TOPIC 2
PERFORMANCE ASSESSMENT
A.Make an output presentation on the demonstration of
the use of publications for predicting tides and currents.
