Predicting the Restless Tides - Photo Tips @ Earthbound Light

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Predicting the Restless Tides

If you've visited my image portfolio, you know that I do a lot of tide pool photography. As you can guess, I have a big need to easily predict when low tide occurs at various locations. When you get to the beach, local agencies often have tide tables posted near the beach parking area, but that's too late. You can also find online tide tables for many areas, but they're not all the same format and of course require internet access to use. For the greatest convenience, I've found that having a standalone program installed is the way to go, and there are two great free ones available.

My favorite tide table program is WXTide which is a port of Dave Flater's Unix XTide program that has been around for years. As such, its core programming is both mature and stable. The Windows version has been around since 1998 and continues to be actively enhanced. WXTide does not run on Mac OS.

Central to WXTide is the Realtime and Graph displays. These are essentially the same with the exception that the Realtime display automatically updates to show data for the current time while Graph allows you to pick the date and time using a scrollbar. Both feature a rising and falling curved line for the tide level on top of a graph with date and time across the bottom and feet (or meters) up the vertical axis. Periods of rising and falling tide are also delineated by blue and green colors (respectively) underneath the tide level curve. Above the curve, time is separated into yellow regions for daytime and blue sections for night. These and other colors can be changed in the Preferences if you so choose. Boaters may appreciate the Realtime capability, but for future planning purposes the Graph display is more useful since you can slide the bottom scrollbar left or right as needed to go backward or forward in time as needed.

The main Graph display in WXTide

Choosing a location near La Push, WA in WXTide

To pick your preferred location (known as a "station" in tidal tracking vernacular) you can use either a text list or a world map. Clicking on the map will progressively zoom it in to the region you are interested in. Right-mouse clicking on the map zooms it back out. Tidal stations that WXTide has data for are shown using colored dots on the map. Hovering your mouse over one of these dots will show tool-tip pop-up with the station name. The text list and the map display are linked too. Clicking on a name in the list moves the map to that location, and clicking on a location on the map updates the text list to have stations listed in order of their distance from where you clicked. If you know the longitude and latitude, you can enter that as well to get you in the ballpark on the station list or map. The default map display is not very high resolution, but an add-on feature is available for download to add World Vector Shoreline (WVS) maps. It's still just an outline of the shoreline, but a much more detailed and accurate one. Rendering this improved map display can tax older machines, but newer ones should have no difficulties.

There are also several other displays in WXTide. The Overview display is intended for more long range planning and features a shorter vertical axis but a much wider time axis. In fact, with the scroll bar in this display it's almost too easy to find yourself years into the future before you realize what you've done. The Clock display shows just a small window showing current conditions. There's also a task bar icon option that shows you how long it is until the next high or low tide. Printable text listings of tide data and tide calendars are easy to generate as well.

Other configuration options in WXTide are too numerous to go into here. While the default display in the program will be sufficient to begin with, you may want to spend some time exploring the many setting choices provided. Just keep track of what you have changed in case you later decide you want to go back to the defaults.

The Overview display in WXTide

Another excellent tide program is JTides by Paul Lutus. Since WXTide runs only on Windows, if you are an OS X user JTides is the solution for you. In fact, since it's written in Java, JTides will run on most anything. Lutus is definitely not a fan of Microsoft, but because Java code is designed to be portable, JTides will run on Windows too. Regardless of your platform, you may find you need to upgrade your computer's version of Java to get JTides to run, but at worst you will have two easy, free programs to install rather than just one. Instructions for doing so are on the JTides web page.

So if JTides runs on Windows, you may be wondering why I prefer WXTide. The main reason is one of coverage. While JTides has an impressive database of over 2,000 locations worldwide, that's nothing when compared with WXTide's 9,500 locations. To see what this means in practice, one of my favorite locations on the Washington coast is Rialto Beach near La Push, WA. WXTide not only knows about La Push, but also the mouth of the Quillayute River between it and Rialto Beach, as well as James Island directly offshore. By contrast, the closest locations that JTides knows about are Cape Alava around 15 miles north of La Push, and Grays Harbor more than 50 miles to the south. You can still get a rough estimate of tidal activity by looking at such nearby locations, but nothing beats the accuracy of having data for exactly where you want to go. WXTide also makes it easy to add new stations by longitude and latitude via the user interface. In theory, one could do the same by manually editing JTide's harmonics configuration file, but after opening it up in WordPad and being a bit overwhelmed, I decided against trying this. If anyone knows how to do so, please let me know.

Picking a location in JTides is not quite as convenient as WXTide is either. You can enter any desired longitude and latitude but from there you must select the actual station name from a text list rather than a map. You can pick multiple stations though and the program will open each in a separate tab across the bottom of the program window so you can easily toggle between them.

The main display in JTides

The color-coded display of monthly tidal activity in JTides

JTides does have one very cool feature though that nothing else can do. It has a colored display of monthly tidal activity with times across the bottom and dates up the side. At each intersection is a color-coded representation of the tide level. Brighter colors are higher levels and darker colors are lower tides. It makes a great tool for researching the best time for the next month to be at a given location,

JTides has a tidal chart display and tide calendar similar to WXTide that are very nicely implemented. It can also export tide data and sunrise/sunset data as a tab-separated file and generate HTML web pages with monthly tide calendars covering the entire year for your selected location.

All in all, I like JTides, but based on the locations in its database, the program is obviously geared more towards sailors than beach combers or even fishermen. More locations would definitely add to the usefulness of JTides at least for my needs.

Both programs (and of course this article about them) come with the obligatory warnings that while they have strived to provide accurate information, they can not be responsible for typographical and other data errors as well as weather variances and human activity that may lead to erroneous results. They work great for tide pool research but should not be relied on for situations where property or human life are at stake. There, I said it.

Update 3/18/2007 - Reader SP wrote to let me know about a great option for OS X users that I was unaware of. Like WXTides, Mr. Tides is based on the UNIX XTides program so it shares a lot with it in terms of look and feel. But the author, August H., has done a nice job of giving it that "Mac OS" feel as well. Nice touches include the excellent calendar display as well as previous and next date selection widgets in the Day and Week views. Mr. Tides displays can include sunrise and sunset information and all information can be exported to iCal. Location selection is well handled as well with map views and its database seems fairly complete based on a quick survey of places I like to go.

I also neglected to mention cTides, an XTides port for Windows Mobile and PocketPC. I've had it running for a while now on my new Windows Mobile 5 smartphone although I haven't taken it to the beach yet. Its features are somewhat scaled down from the others mentioned here owing to the size of the platform it is running on. Also unlike the others though, it appears that cTides has not yet been updated for the recent Daylight Saving Time changes. That's unfortunate, but I can live with it so long as I am aware of it.