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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Tide Prediction Info. Sources (fwd)**

**From:**Wayne Spivak

**Date:**1995 May 13, 07:43 EST

>From Rec. Boats: The subject of sources of tide prediction information comes up so often I thought it would be helpful to post a list of sources. If anyone wants to includes this information in an FAQ, please feel free. There are two agencies that publish readily available documents. They are NOAA and the British Admiralty. My copies of the Admiralty pubs. are several years old so there may be new ones or revised editions. --------------------------------------------------------------------- NOAA - Special Publication No. 98, "Manual of Harmonic Analysis and Prediction of Tides" This publication was first published in 1924 and the current edition (1958?) was reprinted in 1994. It has a more rigorous treatment of the subject than the Admiralty pubs. One of the best deals around. It costs $29.00 and comes with a package including: Fortran program to compute tides. Fortran program to compute tidal currents. Booklet discussing programs and methods. Booklet discussing tides in general. - Harmonic Constants These come on a diskette and on paper. The computer format can be used as input to the programs mentioned above. At $10.00 per station they are expensive when you consider that they have been paid for many times over by our taxes and sales of tide tables. They could be posted on an ftp server for all of us taxpayers to download. Nonetheless that is the way our government is going so, why complain? It is certainly easier to pay $10.00 and get data one can trust than to go to the trouble of computing them oneself. On the plus side, the people at NOAA are very helpful and pleasant to deal with. All available from NOAA at: NOAA/National Ocean Service Attn: Tidal Predictions, N/OES33 1305 East-West Highway Silver Spring, MD 20910 301-713-2815 301-713-4501 fax --------------------------------------------------------------------- Admiralty - N.P. 122(1), "The Admiralty Method of Long Period Observations for Harmonic Tidal Analysis", a.k.a. "Admiralty Tidal Handbook No. 1" Designed to be used with a month of hourly tide/tidal current data or combining several 30 day analyses over about a year. Can produce constants for about 70 constituents. It has a discussion and flow chart to aid in converting the graphical method to a computerized one. - N.P. 122(2), "Datums for Hydrographic Surveys (and other related subjects)", a.k.a. "Admiralty Tidal Handbook No. 2" The name says it all. I don�t think this one is necessary to use the analysis methods presented in N.P.122(1) and N.P. 122(3). - N.P. 122(3), "The Admiralty Method of Harmonic Tidal Analysis for Short Period Observations", a.k.a. "Admiralty Tidal Handbook No. 3" Similar to N.P. 122(1), but for periods of less than one month. Produces 4 constituents (M2, S2, K1, and O1) with quarter-diurnal shallow water corrections with as few as 25 hourly observations. - N.P. 112{a), "Semi-graphic Analysis of 30 Day Tides" This is a worksheet necessary when using the long period method described in N.P. 122(1) - N.P. 112{b), "Semi-graphic Analysis of 30 Day Tides" This workbook is also necessary when using the long period method described in N.P. 122(1) - N.P. 159, "Admiralty Method of Tidal Prediction" If you already know some of the constituents (M2, S2, K1, and O1) for a location, this book has instructions and forms for determining hourly tides. N.P. 203 has these constituents for hundreds of locations. - N.P. 171 This form is used with the short period method described in N.P. 122(3). - N.P. 203, "Admiralty Tide Tables and Tidal Stream Tables" Three volumes by geographical region. Vol 3 is the Pacific Ocean. Contains some of the numbers needed for the long period analysis. It may also be needed for the short period analysis. It may also be possible to calculate the numbers from information given in N.P. 122(1). SUMMARY: The Admiralty pubs tend to be more intuitive and less mathematical than Pub. 98 from NOAA. They focus on providing a usable, although not simple, method of analyzing tide or tidal current (tidal stream in British) data to determine harmonic constants. I initially bought N.P. 122(1,3) and as I read, I found that I needed more and more publications. I hope the list above is complete. I don�t recall the price of all of them, but they were in the $10-$25 range. N.P.112(a) was probably less since it is a single large sheet of paper. Available from any chart dealer that has an account with the Admiralty, although they usually have to be special-ordered. Some examples on the west coast are: Tradewind Instruments - Alameda, CA 510-523-5726 BC Navigation - Sausalito, CA 415-331-6513 Captain�s - Seattle, WA 206-448-2278 --------------------------------------------------------------------- Greg Cook gacook@netcom.com -- Wayne Spivak SBA * Consulting: Systems for Business & Accounting SBA.NET.WEB: Internet & World Wide Web Consulting Tel: 516-221-3306 Fax: 516-221-7129 Internet: Waynes@netcom.com http://www.ronin.com/SBA