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TIDES.DOC DOCUMENTATION FOR TIDES - VERSION 2.00 - 1991 APR 14 Edward P. Wallner 32 Barney Hill Road Wayland, MA 01778-3602 (508)-358-7938 (Note: Recent changes and additions are underlined) This is a program for predicting the height of the tide or the strength of the tidal current at various stations. It runs on IBM compatible machines under MS-DOS or IBM-DOS. The method and format followed in the predictions are generally those used by the National Ocean Service (NOS) in the standard tide and current tables. This program may be freely copied and used for non-commercial purposes. If you find it useful a contribution of $15 is requested. In any case feel free to use the programs and pass them on without alteration and without charge. The author assumes no responsiblity for any errors in the program or the predictions. Detailed predictions are made for high and low water (or maximum ebb and flood) at reference stations for which the tidal constants have been derived from observations made over a long period of time. The tides for subordinate stations are found by making corrections to the times and heights (or speeds) at the reference stations. The predictions for subordinate stations are less accurate than for reference stations, particularly for the lower high and higher low water where tides are nearly diurnal. Current floods/ebbs at subordinate stations may also be less accurate. For stations where the current is rotary the current along the principal axis is predicted. The times and speeds of flood and ebb in these cases are approximate. The TIDES program predicts the height of the tide or strength of the current at any time. The values at reference stations are of the same order of accuracy at any time as for the high/low or flood/ebb values. The predictions for subordinate stations may be less accurate at intermediate times, the more so the larger the differences from the reference station REQUIREMENTS AND CHARACTERISTICS TIDES should run on any IBM machine or compatible with 128K of free memory and the text output should be OK on any printer. The plot of tide heights on the monitor works on the Color Graphics Adapter (CGA) board and on the printer uses codes for the EPSON (IBM extended ASCII.) Special codes to set up NEC pinwriter printers are also available. TIDES.EXE, the executable version of the prediction program, runs with or without an 80x87 coprocessor. TIDES computes the highs and lows for Boston for a month in about 1½ minutes on an IBM-XT with an 8087 coprocessor, and in about 38 minutes without an 8087. (An 8087 coprocessor can be bought for less than $100 and is a good investment if you do much number crunching, such as tidal predictions. For systems with a 80286 or higher chip the program is reasonably fast without a coprocessor.) Predictions for Boston and New York for 1986 agreed with the standard tables to the minute and tenth of a foot for most cases with some times off by 2 or 3 minutes and an occasional difference of .1 or .2 foot. Currents in Cape Cod Canal were generally within 0.1 knot. (If the tide level remains nearly constant for an extended period the predicted time of high of low can vary considerably but the height will still be accurate.) Predictions should be accurate for any era within a few centuries of the present unless the physical conditions at the station change. Accuracy increases very slightly using short prediction intervals. Intervals much greater than one year may lead to significant error and those greater than 480 days are rejected. The source program TIDES.BAS is written in QuickBASIC. In order to fit a good selection of station constants on the distribution disk, the source program is omitted. It is available to contributors on request. PROGRAM OPERATION Just enter TIDES and follow the prompts exactly, filling in zeros if required by the prompt format. When TIDES is run the highs and lows for the next week are first computed for a chosen default station, then a menu is given. In general entering "Q" will stop any operation and return you to the menu. When the "CHANGE STATION" or "CHANGE DEFAULT STATION" option is executed a list of stations for which tidal constants have already been stored in the TIDES format is shown, including the file names under which they are kept. The first pages give all of the U.S. reference stations except those in Alaska. The following pages show a selected set of stations for a specific area. The next page is shown when M is pressed and the list is restarted from the top when R is pressed. When the desired station is on the screen press S to stop paging. You will then be prompted to enter the station file name which is shown in parentheses after the station coordinates. The root directory can hold only 112 files so some disks include more files in an additional directory, e.g. /VIN FOR Martha's Vineyard and /KEYS for the Florida Keys. These directories include a list of the station files named STALIST.XXX which may be added to the STALIST.T&C used by the program. The list can be edited using EDLIN or any other text editing program. For example undesired stations can be eliminated and other station titles moved to the desired line. The station names and locations stored in file STALIST.T&C are displayed by the program as a reminder, but the name of any file of data in the TIDES format can be used whether it is on the screen or not. New stations for which no data file exists can be created using menu option H. The main menu gives options for computing and printing highs and lows, for computing and printing hourly heights, for plotting heights at a given interval (0.5 hours generally works well), for computing the height at specified dates and times, for changing the time interval and station, for changing the default station, for creating additional data files, for changing from metric to English units or vice-versa and for printing the astronomical and constituent factors entering the predictions (used mainly for verifying the program). The equivalent quantities are computed for tidal currents. The printed output can be redirected to a file instead of the printer. The output will be an ASCII file which can be edited using any text editor. CREATING ADDITIONAL DATA FILES Option H is used to generate data files for the TIDES program both for stations for which harmonic constants are available and for subordinate stations, for which only differences from a reference station are available. First a title and file name for the station are entered. The prompt for the title has places for the latitude and longitude of the station which are optional inputs for better identification and do not affect the computation. For stations for which harmonic constants are available you are then prompted to enter the type of station (tide, current, or hydraulic current) and the amplitude and epoch of each of 37 tidal constituents. The constants are entered in sequence from the NOS form 444 of "Standard Harmonic Constants for Prediction", columns B (?.??xH) and D (k'). If there is no data in column B, use column H (Amplitude). If the amplitude of a constituent is zero entering "0" or just a carriage return will enter 0 for both the amplitude and epoch. The modified epoch D (k') should be entered as a number from 0 to 360; ignore any minus sign in column D. Several minor constituents can optionally be inferred from the major constituents if they are not entered directly. This generally gives a slight improvement in accuracy at the cost of a slight increase in running time. For subordinate stations the corresponding reference station data must have been entered. The list of stations for which data is already stored is shown and the file name of the reference station entered. The time differences between the reference and subordinate stations at high and low (or maximum flood and ebb) are entered, then the height differences. In some cases the range of the tide at both stations is requested, as is the maximum flood and ebb for current stations. This data can be taken from Table 2 of the NOS tide or current tables. When Option H is run the title of the new station is added to the end of the STALIST.T&C file. This file must be edited if it is desired to place the station title in a different line. DATA SOURCES A list of places for which I currently have harmonic constants is given at the end of this document. The harmonic constants for various North American reference stations are published by: National Oceanographic and Atmospheric Administration National Ocean Service N/OMA132 Rockville, Maryland 20852 I have a complete set of this data for all U.S. reference stations, about 76 other U.S. stations and many stations in British Columbia (see BCLIST.TXT for a list of these.) I will send a copy of a limited number of station constants and subordinate station corrections if you will let me know the area of interest and send a stamped self addressed 9¼"x4" envelope. The stations for which constants are available are listed below. The International Hydrographic Organization maintains a data bank of tidal constants for 4208 stations worldwide. If you wish constants for foreign locations send me the latitudes and longitudes (to the nearest minute) with a self addressed, stamped envelope and I will eventually send the constants for the closest station in the IHO data set. (The IHO data uses the symbols H for amplitude and G for phase in place of k'.) The tide tables published by the British Admiralty give data for use in their Simplified Harmonic Method of Tidal Prediction. This data is given for about 4400 tide and 148 current stations world wide. A PC program implementing this method is also distributed. Harmonic constants are given for M2, S2, K1 and O1 as well as data from which M4, M6, S4, S6, MS4, MSf, Sa and SSa can be computed. Predictions of about the same accuracy can be made with TIDES if inferred constants are included in the data file. Differences for tides and currents for subordinate U.S. locations are given in the annual tables published by the National Ocean Service. In 1989 the datum to which height of tide is referred was changed from mean low water to mean lower low water for all U.S. stations. Though the difference is generally only a couple of tenths of a foot or less, data should be taken from 1989 or later tables. The constants themselves do not change appreciably over many years so any later table can be used. The theory used in the TIDES program is given in: Manual of Harmonic Analysis and Prediction of Tides Paul Schureman Coast and Geodetic Survey Special Publication No.98 U.S. Gov't. Printing Office, Washington D.C. 1941 This book has been reprinted recently and is available from NOS for $5.00. A supplement to this document, "Computer Applications to Tides in the National Ocean Survey" is also available from NOS at no cost. MISCELLANEOUS The present version of the program does not give predictions of slack water at current stations and for rotary currents the north and east components of velocity must be predicted separately at hourly intervals and combined vectorially by the user. If there is a demand for these features I may get around to adding them sometime. Starting in the 1989 tables the datum was changed to mean lower low water for all U. S. ports, which meant a change of a few tenths of a foot in Z0 (item 1, line 2 of -.TID data files) for ports on the Atlantic coast. The new values have been used in the data on this disk. New constants have also been used for Eastport starting in 1989. If you have any suggestions, comments or problems please let me know. HARMONIC CONSTANTS ARE AVAILABLE FOR THE STATIONS LISTED BELOW REFERENCE STATIONS COVERED BY NATIONAL OCEAN SURVEY TIDES - EAST COAST Albany, New York Punta Palmas, Venezuela Amuay, Venezuela Philadelphia, Pennsylvania Baltimore, Maryland Portland, Maine Boston, Massachusetts Reedy Point, Delaware Breakwater Harbor, Delaware St. Marks River Entrance, Florida Bridgeport, Connecticut St. Petersburg, Florida Caleta Percy, Magellan Strait, Chile*** Charleston, South Carolina Sandy Hook, New Jersey Cristobal, Panama San Juan, Puerto Rico Eastport, Maine Savannah, Georgia Galveston, Texas Savannah River Entrance, Georgia Hampton Roads, Virginia Suriname Rivier, Surinam Isla Zapara, Venezuela Tampico Harbor, Mexico Key West, Florida Washington, D.C. Mayport, Florida Willets Point, New York Maimi Harbor Entrance, Florida Wilmington, North Carolina Mobile, Alabama New London, Connecticut Newport, Rhode Island New York, New York Pensacola, Florida Punta Gorda, Venezuela TIDAL CURRENTS - EAST COAST Baltimore Harbor Approach, MD Mobile Bay Entrance, FL Boston Harbor, MA Pollock Rip Channel, MA Cape Cod Canal, MA Portsmouth Harbor Entrance, NH Charleston Harbor, SC St. Johns River Entrance, FL Chesapeake & Delaware Canal Savannah River Entrance, GA Chesapeake Bay Entrance Tampa Bay Entrance, FL Delaware Bay Entrance The Narrows, New York Harbor, NY Galveston Bay Entrance, TX The Race, Long Island Sound Hell Gate, East River, NY Throgs Neck, Long Island Sound Key West, FL Vieques Passage, Puerto Rico Miami Harbor Entrance, FL TIDES - WEST COAST Aberdeen, Washington Matarani, Peru Anchorage, Alaska *** Astoria, Oregon Balboa, Panama Nikishka, Alaska Buenaventura, Columbia Nushagak Bay, Alaska Callao, Peru Port Townsend, Washington Cordova, Alaska Dutch Harbor, Alaska Puntarenas, Costa Rica Guayaquil, Ecuador St. Michael, Alaska Guyamas, Mexico Salina Cruz, Mexico Honolulu, Hawaii San Diego, California Humboldt Bay, California San Francisco, California Juneau, Alaska Seattle, Washington Ketchikan, Alaska Seldovia, Alaska Kodiak, Alaska Sitka, Alaska Kwajelein Atoll, Marshall Is. Sweeper Cove, Alaska La Union, El Salvador Los Angeles, California Talara, Peru Massacre Bay, Alaska Valdez, Alaska TIDAL CURRENTS - PACIFIC COAST Admiralty Inlet, WA Rosario Strait, WA Akutan Pass, Aleutian Islands San Diego Bay Entrance, CA Ch'ang Chiang Entrance, China San Francisco Bay Entrance, CA Deception Pass, WA San Juan Channel (S. Entrance), WA Grays Harbor Entrance, WA Sergius Narrows, AK Huang P'u Chiang, China Strait of Juan de Fuca Entrance Isanotski Strait, AK The Narrows, Puget Sound, WA Kvichak Bay, AK Unimak Pass, Aleutian Islands North Inian Pass, AK Wrangell Narrows, AK *** Complete prediction requires more than 37 constituents. OTHER TIDE STATIONS Alameda, CA Apalachicola, FL Apia, Samoa Islands Aquia Creek, Potomac River, VA Aransas Channel, TX Arthur Harbor, Palmer Station, Antarctica Atlantic City (Steel Pier), NJ Avon, NC Bar Harbor, ME Bayou Rigaud (Grand Isle), LA Bayshore, L.I., NY Bay St. Louis, MS Bears Bluff, N. Edisto R., SC Block Island (Old Harbor), RI Boca Congrejos, Isla Verde, PR Buzzards Bay Entr, Cape Cod Canal, MA Burntcoat Head, Nova Scotia Canton Island, Phoenix Is., S. Pac. Cape Cod Canal, E. Entrance, MA Cape Hatteras (Fishing Pier), NC Cape May (ferry terminal), NJ Cape Steenboom, New Guinea Carlos Point, Estero Bay, FL Charleston, OR Chesapeake Beach, MD Coconut Point, FL Colonial Beach, VA Constantine Harbor, AK Crescent City, CA Daytona Beach, Fl Daytona Beach Shores (Sunglow Pier), FL Elkhorn Slough, CA Esbjerg, Denmark Friday Harbor, San Juan Island, WA Galveston, Pleasure Pier, TX Garibaldi, OR Guam (Apra Harbor), Marianas Hirtshals, Denmark Indian River Inlet, DE Lewisetta, Potomac River, VA Turkey Point, FL La Jolla, CA Eureka, CA Point of Pines, SC Port San Luis, CA. Neah Bay, WA Cross Island, AK Nantucket, MA Malakal Harbor, Palau Is. Caroline Is. Matanzas Pass, Estero Island, FL McMurdo Sound, Antarctica Mokuoloe Island, HI Montauk, Long Island, NY Monterey Harbor, CA Morehead City, NC Moss Landing, CA Myrtle Beach (Springmaid Pier), SC Naples, FL New Bedford, MA Newport Bay, CA Nikiska, Cook Inlet, AK Old Saybrook Point, CT Padre Island (South End), TX Ponape Harbor, Caroline Islands Port Aransas, TX President Channel, Orcas Is., WA Providence, RI Puerto Soberania, Palmer Peninsula Punta Tunas, PR Reykjavik, Iceland Rincon Island, CA Rockland, ME Sabine Pass, TX Saint John, New Brunswick Seavey Island, ME Shell Point, FL Southbeach, OR Stamford, CT Tarawa, Gilbert Islands Toke Point, WA Virginia Beach, VA Wachapreague, VA Wallops Island, VA Yakutat, AK INterNATIONAL HYDROGRAPHIC ORGANISATION DATA Banyuls, France Socoa, France Toulon, France Marseille, France Saint Servan, France Cherbourg, France Nice, France Venezia, Italy Grado, Italy Esbjerg, Denmark Aarhus, Denmark Hirtshals, Denmark Saint John, New Brunswick, Canada Burntcoat Head, Canada Grand Turk, UK Cabo San Lucas, B.C.S., Mexico La Paz, B.C.S., Mexico Magdalena Bay, Mexico San Carlos, B.C.S., Mexico Topolobampo, Sin., Mexico San Juanico Bay, Mexico Yavaros, Son., Mexico Ballenas Bay, Mexico Guaymas, Som., Mexico Isla Guadalupe, B.C., Mexico Bahia de los Angeles, B.C., Mexico Puerto Penasco, Son., Mexico Ensenada, B.C., Mexico Salina Cruz, Oax., Mexico Matavia, Tahiti, France Motuoini, Tahiti, France Nuku'alofa, Tonga Urangan Jetty, Australia Brisbane Bar, Australia Caloundra Heads, Australia Brisbane (W. Inner Bar), Australia Snapper Rocks(Danger Point), Australia Ballina, Australia Iluka, Australia Victoria Dock, Singapore Horsburgh Lighthouse, Singapore Tg. Segenting, Malaysia Colombo, Sri Lanka Hong Kong, UK Kao-Hsiung, China Fujairah, Oman (U.A.E.) Naha Ko, Japan Kobe, Japan Nagoya, Japan Sinko, Yokohama, Japan CANADIAN DATA Constants for all reference tide stations in the NOS tables for the East and West coasts are available as well as many stations in British Columbia. Tidal current constants for Grand Manan Channel (Bay of Fundy Entrance) are also on hand.