Received: from hplms26.hpl.hp.com by opus.hpl.hp.com with SMTP (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA14530; Tue, 10 Jan 1995 15:34:11 -0800 Return-Path: <jackg@cache.crc.ricoh.com-DeleteThis> Received: from cache.crc.ricoh.com by hplms26.hpl.hp.com with SMTP (1.36.108.4/15.5+ECS 3.3+HPL1.1S) id AA08462; Tue, 10 Jan 1995 15:34:25 -0800 Received: by cache.crc.ricoh.com (5.57/Ultrix3.0-C) id AA12862; Tue, 10 Jan 95 15:30:09 -0800 Received: from localhost by downhaul.crc.ricoh.com (4.1/SMI-4.1) id AA04134; Tue, 10 Jan 95 15:28:27 PST Message-Id: <9501102328.AA04134@downhaul.crc.ricoh.com-DeleteThis> To: wind_talk@opus.hpl.hp.com-DeleteThis Subject: Tides Date: Tue, 10 Jan 1995 15:28:27 -0800 From: Jack Greenbaum <jackg@cache.crc.ricoh.com-DeleteThis>
Storm sailing isn't my idea of fun (been there, done that), so I
undertook geeky activities this weekend and finally prepared the SF bay
area data file for the TIDES program. I've placed tides.zip and
sf-tides.zip (data only) on my local ftp site:
ftp://ftp.crc.ricoh.com/pub/tides/
It give somewhat different tide numbers than Ken's emails have, but they
are certainly well correlated. The current speed numbers match the "one
hour" rule of thumb for slacktime, so they seem reasonable as well. The
author claims extremely close correlation with government tables. (NOTE:
The "graphics" output of this program is horrible, if you want graphs
you'll want a spreadsheet or some other thing.) I've used this program
for almost two seasons.
I paid the registration fee, and the author has sent me the data for our
lovely bay which I have typed in for you're enjoyment. The sf-tides.zip
file contains the data for the following:
Current stations --
San Francisco Bay Ent
Oyster Point, 2.8 miles east of
Little Coyote Pt., 1.2 nmi. NE of
San Mateo Bridge
Dumbarton Bridge
Berkeley Yacht Harbor, 0.9 nmi. south of
CARQUINEZ STRAIT, CA - (MAJOR AXIS)
Davis Point, 1.0 nmi. NW of
Sherman Island East, 0.2 mile north of (on Sacramento river)
Tide stations --
San Francisco (GOLDEN GATE)
Sausalito
Hunters Point
Oyster Point Marina
Coyote Pt. Marina
San Mateo Bridge (west end)
San Mateo Bridge (east end)
Dumbarton Bridge
Palo Alto Yacht Harbor
Berkeley
Alameda
Ocean Beach
Princeton, Halfmoon Bay
Santa Cruz
Moss Landing (OCEAN PIER)
Monterey Harbor
Here's the part of the docs for the program (let me know if you'd like
the complete doc file). The author is sending me a more recent version,
but the features are the same as far as I know. I'll send mail if the
new version is significantly better.
DOCUMENTATION FOR TIDES - VERSION 2.16 - 1993 JUN 26
Edward P. Wallner
32 Barney Hill Road
Wayland, MA 01778-3602
(508)-358-7938
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. Feel free to try the program and pass it on without
alteration and without charge. If you use the program a $15
registration fee must be paid.
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
[...]
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 or 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 registered users on
request.
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