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News

XTide 2.10

Get it from http://www.flaterco.com/xtide/files.html#xtide.

Prebuilt Windows binary

A prebuilt Windows binary for the command-line client is available for downloading from http://www.flaterco.com/xtide/files.html#contrib.  See the readme included in the zip file for important details.  Thanks to Leonid Tochinski.

FAQ of the Day:  "Are these predictions compliant with the new 2007 Daylight Savings Time rules for the U.S.?"

XTide relies on the de facto standard time zone database to handle Daylight Savings Time.  XTide's results will obey the new Daylight Savings Time rules if and only if the version of zoneinfo installed is sufficiently new.  See System Requirements.

Harmgen 3

Harmgen, the package for deriving harmonic constants from water level observations, has been renovated and its integration with Congen and Harmbase has been improved.  Get it at http://www.flaterco.com/xtide/files.html#experts.

Congen 1.6

Congen 1.6 is a complete rewrite of the package for generating the speeds, equilibrium arguments, and node factors of tidal constituents.  In addition to the classic command-line interface provided by Congen 1.5, it now includes a C++ library that can be used directly by other programs.  Get it at http://www.flaterco.com/xtide/files.html#experts.

tideEditor 1.4.1

Changes in tideEditor 1.4 include the ability to view and edit all fields in the latest harmonics file and improved error checking.  Get it at http://www.flaterco.com/xtide/files.html#extras.

PHP Special Interest Group

A number of people have expressed interest in getting XTide to work through PHP.  Thus far I have just been introducing them to each other through e-mail and waiting for cool things to happen.  There is now a WordPress plugin by Mir Rodríguez.

Native OS X port

Lee Ann Rucker has done a nativized port to OS X using Cocoa and Objective-C.  It is available at http://homepage.mac.com/lrucker/XTide/.

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.

Roadmap to future development

Things worth fixing / TO-DO list

Data maintenance

There is great demand for a centrally maintained, royalty-free, authoritative database of all tide stations in a standardized format.  Such a database does not exist.

It takes a great deal of effort on my part to scrape tide data from interactive web sites and transform them into a coherent database for use with XTide.  That database is then used by numerous projects, both open source and commercial, because it is the closest thing to a centrally maintained, royalty-free, authoritative database that is available.  I do not get paid to do this.  It's a huge amount of work with a steep learning curve attached, and nobody else will do it.

As onerous as it is just to update the data for the U.S. once a year, I cannot afford to import and maintain any data whose quality is suspect or where no reliable source for future updates exists; nor can I afford to engage in activism to try to persuade tide authorities to release more data.

All of the tools that I use are open source and available for download from http://www.flaterco.com/xtide/files.html.  The Tide Constituent Database (TCD) library is even public domain.  I hope that someday tide authorities will use it to produce TCD files that they distribute directly, and then my role in this will become redundant.

• Either get more German data or regenerate using the old data and fewer constituents
• Maybe create a currents database using legacy constants + new offsets, for lack of something better
• Italian data (2008-02-23)
• Maybe scrape the simplified harmonic constants from the Norwegian Hydrographic Service—acceptable use TBD
• Lots of inactive Canadian stations might be usable
• Determine status of non-U.S. locations appearing on NOS web site

xtide

• Investigate pcal interoperability problem.  Why won't it import iCal?
• Unbundle Dstr?

libtcd

• 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

tcd-utils

• Fix truncation of notes by build_tide_db
• build_tide_db recognize datumkind field name

Harmbase2

• Clean up the code.
• Do one-time hack to convert renamings-USA from prefix form to postfix form for sub stations that get a "context" (may be rendered moot by additional web site changes)

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 http://www.pac.dfo-mpo.gc.ca/sci/osap/projects/tidpack/tidpack_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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