Article 12690 of alt.sources:
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From: dave@case50.ncsl.nist.gov (David Flater)
Newsgroups: alt.sources
Subject: XTide 1/4
Date: 7 Aug 1995 13:46:09 GMT
Organization: National Institute of Standards and Technology
Lines: 603
Message-ID: <4055f1$vb@dove.nist.gov>
NNTP-Posting-Host: case50.ncsl.nist.gov
Keywords: tide

Submitted-by: dave@case50.ncsl.nist.gov
Archive-name: xtide-1.0.1/part01

This program uses the harmonic method to display tide levels either as
a tide clock (showing the current level) or as a graph.  Please refer
to README for more information.

THIS PACKAGE IS AVAILABLE FOR ANONYMOUS FTP FROM:
ftp://speckle.ncsl.nist.gov/flater/sources/xtide-1.0.1.tgz

An illustrated, HTML-ized version of the README is available at:
http://case50.ncsl.nist.gov/xtide/xtide.html

#!/bin/sh
# This is xtide-1.0.1, a shell archive (shar 3.21)
# made 08/07/1995 13:41 UTC by dave@case50.ncsl.nist.gov
# Source directory /home/dave/xtide-1.0.1
#
# existing files WILL be overwritten
#
# This is part 1 of a multipart archive                                    
# do not concatenate these parts, unpack them in order with /bin/sh        
#
# This shar contains:
# length  mode       name
# ------ ---------- ------------------------------------------
#  17982 -rw------- GPL
#    100 -rw------- Imakefile
#  15353 -rw------- README
#    155 -rw------- config.h
#  24861 -rw------- harmonics
#  28038 -rw------- xtide.c
#
if touch 2>&1 | fgrep '[-amc]' > /dev/null
 then TOUCH=touch
 else TOUCH=true
fi
if test -r @shar_seq_.tmp; then
	echo "Must unpack archives in sequence!"
	next=`cat @shar_seq_.tmp`; echo "Please unpack part $next next"
	exit 1
fi
# ============= GPL ==============
echo "x - extracting GPL (Text)"
sed 's/^X//' << 'SHAR_EOF' > GPL &&
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SHAR_EOF
$TOUCH -am 0805102495 GPL &&
chmod 0600 GPL ||
echo "restore of GPL failed"
set `wc -c GPL`;Wc_c=$1
if test "$Wc_c" != "17982"; then
	echo original size 17982, current size $Wc_c
fi
# ============= Imakefile ==============
echo "x - extracting Imakefile (Text)"
sed 's/^X//' << 'SHAR_EOF' > Imakefile &&
XCCOPTIONS =
XDEPLIBS = $(DEPXLIB)
XLOCAL_LIBRARIES = $(XLIB)
XLDLIBS = -lm
X
XSimpleProgramTarget(xtide)
SHAR_EOF
$TOUCH -am 0805102495 Imakefile &&
chmod 0600 Imakefile ||
echo "restore of Imakefile failed"
set `wc -c Imakefile`;Wc_c=$1
if test "$Wc_c" != "100"; then
	echo original size 100, current size $Wc_c
fi
# ============= README ==============
echo "x - extracting README (Text)"
sed 's/^X//' << 'SHAR_EOF' > README &&
X    XTide  Harmonic tide clock and tide predictor
X    Version 1.0.1  DWF  8/5/95  dave@case50.ncsl.nist.gov
X
X    Copyright (C) 1995  David Flater.
X
X    This program is free software; you can redistribute it and/or modify
X    it under the terms of the GNU General Public License as published by
X    the Free Software Foundation; either version 2 of the License, or
X    (at your option) any later version.
X
X    This program is distributed in the hope that it will be useful,
X    but WITHOUT ANY WARRANTY; without even the implied warranty of
X    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
X    GNU General Public License for more details.
X
X    You should have received a copy of the GNU General Public License
X    along with this program; if not, write to the Free Software
X    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
X
X
X    The tide prediction algorithm used in this program was developed
X    with United States Government funding, so no proprietary rights
X    can be attached to it.  For more information, refer to the
X    following publications:
X
X    Manual of Harmonic Analysis and Prediction of Tides.  Special
X    Publication No. 98, Revised (1940) Edition.  United States
X    Government Printing Office, 1941.
X
X    Computer Applications to Tides in the National Ocean Survey.
X    Supplement to Manual of Harmonic Analysis and Prediction of Tides
X    (Special Publication No. 98).  National Ocean Service, National
X    Oceanic and Atmospheric Administration, U.S. Department of
X    Commerce, January 1982.
X
X
XTHIS PACKAGE IS AVAILABLE FOR ANONYMOUS FTP FROM:
Xftp://speckle.ncsl.nist.gov/flater/sources/xtide-1.0.1.tgz
X(The version number may change.)
X
XAn illustrated, HTML-ized version of this README is available at:
Xhttp://case50.ncsl.nist.gov/xtide/xtide.html
X
X** Please read the section entitled WARNING: CONTAINS VERSION 1 SOFTWARE.
X
X
XOverview
X--------
X
XXtide was originally intended to be a "tide clock."  Lots of people
Xdown on the shore have them -- it's just an analog clock that's been
Xmarked with high and low tide, that makes a complete cycle in a bit
Xover 12 hours.  There's just one teensy problem with them, which is
Xthat they are only accurate to within plus or minus 50% of reality.  I
Xfelt kind of stupid having a square thingy on my screen that just went
Xup and down and paid no attention to the actual water level outside.
X
XXtide is now a bit more accurate than that (I hope!), but there's a
Xcost associated:  you need to (somehow) get the harmonic constants for
Xyour location.  This is a set of numbers that tells Xtide everything
Xit needs to know to predict your local tides.  The next section talks
Xmore about harmonic constants.
X
XXtide has two basic modes of operation.  The default mode is to act
Xlike a tide clock, showing the current water level and predicted time
Xof the next high tide.  The water is blue if it is flowing, green if
Xit is ebbing.  You can change the colors with command line switches.
XThe -hairy option causes it to track the tide curve instead of simply
Xshowing the current water level.  See below regarding the -gstretch
Xoption for the hairy tide clock.
X
XThe other mode is graph mode, triggered with the -graph switch.  Graph
Xmode draws a graph of the water level for two days and labels the high
Xand low tides.  By using -gstart with -graph, you can predict tides
Xfar into the future.  The -gstart time spec is in your local time
Xzone; this does not change even if you specify -utc.  Close the window
Xor kill the program to get rid of the graph.
X
XThe -gstretch option lets you adjust how stretched out / crowded the
Xgraph is.  -gstretch 2.0 means that graph mode will stretch one day
Xacross the screen instead of two.  This might help you to read the
Xhigh and low tide predictions if they were too close together.
X-gstretch 0.5 crowds four days in the same amount of space.  -gstretch
Xwill adjust the graph in the hairy tide clock in the same way.
X
XThe tick marks on the horizontal axis are one hour apart, but they are
Xnot calibrated with the top of the hour.  The other tick marks are
Xwhatever units of depth were used for the amplitudes for the location
Xbeing shown.
X
XBy default, all timestamps are displayed in your local time zone.  You
Xcan use the -utc switch to use UTC instead.  There is no switch to use
Xthe time zone of the location being displayed because Unix does not
Xyet support doing Daylight Savings Time conversions for more than one
Xlocale on a given machine; you have to pick one system and use it for
Xeverything.  If you specify an offset with the -tz switch, xtide will
Xdisplay timestamps with that offset and not try to correct for DST.
X
XUsage:  xtide [-bg ...]              Background color
X              [-check YYYY]          Check for errors in equilibrium arguments
X              [-display ...]         X display
X              [-fgfall ...]          Color of ebbing water
X              [-fgrise ...]          Color of flowing water
X              [-fgtext ...]          Color of text and lines
X              [-geometry ...]        X geometry
X              [-graph]               Graph 2 days of tides (modulo gstretch)
X              [-gstart YYYY:MM:DD:HH:MM]  Time at which to start graph
X              [-gstretch N.NN]       Adjust graph detail vs. time span
X              [-hairy]               Show slice of tide graph in the clock
X              [-hfile ...]           Location and name of harmonics file
X              [-list]                List all locations in harmonics file
X              [-location "Name"]     Location to show tides for
X              [-nolines]             Suppress tick marks / depth lines
X              [-test]                Test mode (mostly useless)
X              [-tz [-]HH:MM]         Fixed time zone offset for timestamps
X              [-utc]                 Show timestamps in UTC
X              [-version]             Print XTide version
X
XTime format example -- half past midnight, June 1, 1995:  1995:06:01:00:30
X
X
XYou NEED Harmonic Constants
X---------------------------
X
XYou cannot predict tides for your locale unless you know its harmonic
Xconstants.  Finding out those constants could be a real pain.  I will
Xkeep an updated harmonics file available for anonymous FTP at
Xftp://speckle.ncsl.nist.gov/flater/sources/harmonics, but in all
Xlikelihood your location still won't be in it.
X
XThe first edition of the Manual of Harmonic Analysis and Prediction of
XTides came with a list of constants for lots of locations.  I only
Xhave access to the revised edition, which does not have that list.  It
Xsays, "...the work of maintaining such a list has now been taken over
Xby the International Hydrographic Bureau at Monaco."  I was not brave
Xenough to attempt to contact that bureau, if it even still exists
X(it's been 55 years).
X
XYou can do what I did, and pay the National Ocean Service (in the
XU.S.) ten dollars for one set of constants.  Otherwise, lots of luck.
XIf you do go through the trouble, and the data that you get can be
Xfreely distributed, please send it to me so that I can add it to the
Xend of the harmonics file that I distribute.  If enough people do
Xthis, I might actually assemble a halfway decent database.
X
XIf you send me a set of constants, be sure to preface it with comment
Xlines giving your name, your e-mail address, where you got the data,
Xhow old the data is, and the units used for amplitude.  The age of the
Xdata is significant not only because geographical changes can
Xinvalidate a set of constants, but because the NOS subtly changed the
Xway that it figures tides in 1989.  The difference is minor, but worth
Xknowing about.  It can cause slight discrepancies in the results.
X
X
XThe National Ocean Service and Similar Non-U.S. Organizations
X-------------------------------------------------------------
X
XThe quickest way to get harmonic constants from the NOS is to fax a
Xrequest to 301-713-4436 asking for the 37 constituents for someplace
Xat or near XYZ.  Provide your snail mail address.  They will mail you
Xa bill at the same time that they mail the data.  It will be one or
Xtwo weeks before you get it.  You can call 301-713-2877 if you want to
Xtry to check on its progress.
X
XThere are a number of organizations world wide that are capable of
Xproviding harmonic constants.  I know little about them except that
Xthey exist, and that the system of 37 constituents used by the NOS is
Xnot used by all of them.  The harmonics file that I provided is set up
Xfor the NOS system.  Given sufficient information, you should be able
Xto modify the harmonics file to use whatever system is used by your
Xfavorite organization.  I cannot currently provide harmonics files to
Xwork with every possible system, since I don't know anything about any
Xof them except the one used by the NOS.  However, if you construct a
Xharmonics file for a different system, please send it to me with a
Xdescription of whose system it implements, and I will gladly add it to
Xthis distribution.  I will also include here any information that is
Xsent to me to help other people get harmonic constants from different
Xorganizations.
X
X
XGetting Harmonic Constants from your Back Yard
X----------------------------------------------
X
XIf you are ambitious and have access to regular water level readings
Xfor your locale over the course of, oh, a YEAR or so, you can derive
Xthe harmonic constants yourself.  There is even source code for doing
SHAR_EOF
echo "End of xtide-1.0.1 part 1"
echo "File README is continued in part 2"
echo "2" > @shar_seq_.tmp
exit 0


