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XTide 2.11

   XTide 2.11 fixes a few bugs, adds GPS integration (still somewhat
   experimental) and improves compatibility with the latest window
   managers and libraries.  Get it from
   [3]http://www.flaterco.com/xtide/files.html.

Data quality

   For several years there have been two tide stations for which the
   meridians were set wrong in the data as incoming (ostensibly UTC data
   were actually calibrated to local time).  However, a diligent user
   recently found two stations in California that newly developed this
   problem between December 2008 and December 2009.  As always, please use
   caution and report such problems when they are found.

Mailing list

   There is a manually-maintained, announce-only mailing list to which I
   send notices of each update to XTide or the harmonics data.  You can
   request to join by e-mailing me at dave@flaterco.com.

   Please note:  If an announcement to you gets bounced by your mail
   server, you fall off the list.  Some long-time contributors have fallen
   off because, unbeknownst to them, their ISPs subscribed to a spam
   blackholing service that blackholed all pair.com-hosted domains after
   one of them sent out spam.
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Roadmap to future development

  Things worth fixing / TO-DO list

   Data maintenance

   I refresh the data for the U.S. once a year from the National Ocean
   Service web site.  This is a lot of work and takes up basically all of
   the time and energy that I can devote to data maintenance.

   The coverage of other countries suffered a major blow in 2001 when
   [4]the UKHO claimed to own the copyright on tons of old tide data that
   I had painstakingly processed for XTide.  With the help of some
   diligent volunteers, I eventually managed to source new data for the
   U.K., Germany [[5]*], Netherlands, and Canada.  Since then, a slowly
   growing group of countries has made harmonic constants or water level
   records available on the web.  Usually, the legal terms attached to
   those data are written to grant free license only in the case of direct
   personal or academic use.  The XTide database is not exactly that,
   since the data or a derivative work would be redistributed to untracked
   masses of users, possibly through commercial channels such as packaged
   Linux distributions.  But even if the legalities were cleared up, the
   annual job of pulling data off of a web site, developing ad hoc
   conversion tools that might never work again (even for the same web
   site one year later), cleaning up the converted data, and integrating
   them with the XTide database is too much for me when multiplied by N
   different countries.

   I encourage those tide authorities that are now making harmonic
   constants publicly available on their web sites to package those data
   using the open source tools available from
   [6]http://www.flaterco.com/xtide/files.html and distribute those data
   in TCD files.  Besides making the data traceable to authority with more
   direct quality control, this would eliminate the legal trap of
   determining whether reprocessing and redistributing those data for use
   with XTide is permitted by the terms of use:  such reprocessing and
   redistribution would be unnecessary if the data were already in a form
   that could be directly downloaded and utilized by end-users.

   Failing that, the Sisyphean web-scraping job should be divided among N
   contributors working autonomously.  Any qualified volunteers out there
   who wish to maintain a harmonics database for their own countries may
   begin by clarifying the terms of use for the relevant data with their
   local tide authorities and then download the tools and go do it.
   Following is a list of the data sources that have been brought to my
   attention.  If you succeed, let me know and I'll link to your download
   site. [[7]**]
     * [8]Canada (I only processed the active stations; there are hundreds
       of old, inactive ones)
     * [9]Italy
     * [10]Norway
     * [11]Spain
     * [12]U.K.  (I processed these data once but would gladly hand off
       the maintenance task to someone local.)
     * Miscellaneous
          + [13]University of Hawai`i Sea Level Center
          + [14]National Ocean Service (some locations outside of U.S.
            jurisdiction have historically been included along with the
            U.S. data)

   * The German data were supplied as a rather short time series of water
   level observations from which I derived harmonic constants.  The
   agreement with official predictions was never that hot.  Further
   investigation by Jan Deepen in 2009 revealed significant, uncorrectable
   differences with authoritative predictions, so the German data were
   retired from the database at the end of 2009.

   ** Since a large part of the issue here is legal ambiguities, it would
   be preferable for you to retain control over your files on a server in
   your own country, where any copyright disputes might be resolved in a
   civilized fashion.

   xtide
     * SVG format support (Jack Greenbaum).
     * Renovate to use the latest fad widget toolkit, use scalable
       graphics everywhere, play nice with modern desktop environments.
     * Unbundle Dstr?

   tcd-utils
     * Bug:  build_tide_db loops forever if no <document> tag is found, or
       if the first line of the XML file is blank.  (Not a real parser.)

   libtcd
     * Add const in API where const is due
     * Things not to do unless/until a major revision is needed.
          + Get rid of internal state; fix inability to have more than one
            database open
          + Remove gratuitous complexity in the encoding of speeds,
            equilibrium arguments, and node factors; make speeds 32-bit
            unsigned with no offset
          + Possibly permit node factors to be specified for intervals
            shorter than 1 year and/or support apps that use libcongen to
            generate the node factors themselves

   Harmbase2
     * Clean up the code.

  Suggested XTide features and other etceteras

   The following features have been suggested or thought about but did not
   make the cut.  They could be added in future revisions if there were
   sufficient demand.
     * There ought to be a way to specify relative dates and times in the
       -b and -e fields.  Need an applicable standard; ISO 8601 doesn't
       support it.  Simon Bridger requested -b and -e to recognize
       relative specifications like yesterday, today, tomorrow, mon-sun,
       sat+7 for next Saturday, "tomorrow 23:59" or "sat 00:00".  Others
       want to specify a small relative offset from the current time for
       -b to change the position of the + mark in graphs.
     * Factor out a standalone component library as a favor to developers
       who want to reuse XTide's engine but reinvent its wheels.
     * Generate maps for xttpd navigation and general illustration,
       include in LaTeX form.
     * Graeme Rae suggested a line for the current time in text listings,
       like "2001-03-19 11:50 AM PST 0.10 feet Falling."  This is doable
       now that the tide events code has been refactored, but it's not
       clear what the settings and behaviors should be to handle the "now"
       event consistently across all modes.  Graphs and clocks have their
       own ways of showing the "now," and it would be inappropriate to
       include "now" in a calendar.
     * Simon Bridger requested support for multiple -b and -e
       specifications.
     * Tim Cera notes that Options might be more user-friendly if it was
       split into separate menus for "Create new windows" versus "Change
       settings."
     * Add a real color chooser in control panel.  This would come free
       with Qt or similar if we ever migrated from Athena widgets.
     * Constituent inference was patched in via libtcd and maybe could
       have been integrated better.  In theory, you might want to control
       it on a station-by-station basis like preferred units.  But, maybe
       it's a non-issue.  Nobody has complained yet.
     * Generate node factors and equilibrium arguments more than once a
       year.  Most tide prediction software does it monthly or at least
       does it for the middle of your prediction interval.  But the legacy
       of SP98 is to do it yearly.
     * Add support for Doodson style tide prediction as used by Foreman's
       IOS package.  At this time there seems to be little benefit to be
       gained by doing this:
         1. No new Doodson data appear to be forthcoming.
         2. Most Doodson constituents are approximated fairly well by
            Congen now.
         3. The ones that aren't approximated well are those that are
            drastically affected by latitude.  To support
            latitude-dependent constituents, node factors and equilibrium
            arguments would have to be generated internally to XTide,
            which would be a significant architectural change.
         4. Casement opined that the latitude-dependent method is bogus
            anyway because tides are generated some place in mid-ocean
            with a different latitude.
         5. If you want IOS, you can find it at
            [15]http://www.pac.dfo-mpo.gc.ca/sci/osap/projects/tidpack/tid
            pack_e.htm.
     * Simon Bridger requested a "weekend warrior" option that lists
       today, tomorrow, Saturday, Sunday, and next Saturday.
     * Jef Poskanzer long ago asked for a global plot of tide levels to
       show how the tides move around.  This could be done by color-coding
       the dots on the globe, but it would (1) require a true-color
       display and (2) be too slow to be the default behavior of the
       globe.  Hans Bot has seconded this request.
     * David Mendez suggests plotting the derivative of the tide as well
       as the tide--this is useful for predicting swells.
     * Diane Grant wants to be able to execute a query like 'find all days
       in this year having a flood greater than 3.0 between 8 AM and 9
       AM.'
     * xttpd: Change mapping of locations to URLs so that links won't
       break when harmonics files are changed.  Thought about this but
       could not find a better solution than putting the entire location
       name in the URL, which is already semi-supported by the exact query
       feature.
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References

   1. http://www.flaterco.com/xtide/changelog.html
   2. http://www.flaterco.com/xtide/xtide.html#contents
   3. http://www.flaterco.com/xtide/files.html
   4. http://www.flaterco.com/xtide/faq.html#60
   5. http://www.flaterco.com/xtide/news.html#asterisk
   6. http://www.flaterco.com/xtide/files.html
   7. http://www.flaterco.com/xtide/news.html#asterisk2
   8. http://www.meds-sdmm.dfo-mpo.gc.ca/meds/Databases/TWL/TWL_inventory_e.htm
   9. http://www.apat.gov.it/site/it-IT/Servizi_del_sito/Guida/
  10. http://vannstand.statkart.no/Engelsk/harm.php
  11. http://www.puertos.es/en/oceanografia_y_meteorologia/banco_de_datos/nivel_del_mar.html
  12. http://www.pol.ac.uk/ntslf/data.html
  13. http://uhslc.soest.hawaii.edu/
  14. http://tidesandcurrents.noaa.gov/
  15. http://www.pac.dfo-mpo.gc.ca/sci/osap/projects/tidpack/tidpack_e.htm
  16. http://www.flaterco.com/xtide/changelog.html
  17. http://www.flaterco.com/xtide/xtide.html#contents
