09 - Tides and Currents On Your Mobile Phone
Several Free Programs Allow You to Check Tides and Currents From Just About Anywhere.

For some boaters tides and currents are something to think about only rarely. For others, they are a constant concern. Our home port is on Penobscot Bay in Maine - the land of the 10-foot tides - so we think about them every time we step aboard.

No matter where your home port is, if you spend enough time on the water, you will need to think about tides and currents - and these considerations can be critical. They can save fuel costs and time, but they can also impact safety when entering an ocean inlet or docking in an unfamiliar port.

While checking tide and current predictions is traditionally done using tide tables, today there are many great options that allow you to enter a location and receive the predictions electronically on your laptop or mobile phone. We like using the phone because, like weather or navigation information, this data is nice to have in your pocket.

Indeed, there are few pieces of information that are more practical. For example, tidal information can be useful in almost any anchoring situation. In Maine, knowing how high the tides are and where you are in the tide cycle is a requirement. Fail to include the 10-foot tide in your scope calculations and you could drag the anchor in the middle of the night or even go aground. Tide Tool Tide Tool is free, reliable, covers almost 7,000 locations and has a smart graphic display.

Every summer brings some visiting yachtsman who comes into the harbor at high tide, finds the perfect anchorage in 12 feet of water and, failing to consider the 10-foot tidal drop, ends up aground at low tide. With our rocky bottom, this phenomenon provides good business for local boatyards but can be so easily avoided by consulting a good tide prediction program.


The first thing to understand is that, whether you are looking at data electronically or on paper, they are only predictions. Calculating tides and currents at a specific location at a given time involves a highly complex mathematical formula based on approximations and previous observations. While these predictions are often quite accurate, you still must be diligent and observe the conditions that surround you.

Reliable tide and current predictions can be found on the Internet or you can download a program that will run on your mobile phone. We prefer tides to be calculated on the mobile phone itself. When pulling into a remote anchorage, it's important that we are able to get a good tide estimate, and we don't want to be at a disadvantage because we couldn't get online. We are especially fond of the graphical applications that provide a quick visual reference for the tide height, as well as our current position in the cycle.

Fortunately, there are some excellent tide and current prediction programs for the iPhone, Palm OS and Windows Mobile mobile phones. For Blackberry and Symbian you will need to use one of the many tide and current prediction websites.

The most common software program for tide and current predictions is XTide, an open source tide prediction program that came out of the National Institute of Standards and Technology, and was written by Dave Flater. XTide was designed for Unix computers but has been translated to work on other operating systems. It has been around for more than 30 years. Thanks to XTide's freeware status, there are free tide and current programs available for many mobile phones.

Our favorite, which we have used for years, is Tide Tool. Tide Tool is reliable, has a great user interface and works blazingly fast. There is support for nearly 7,000 stations worldwide, and the graphical display allows you to quickly see where you currently are in the tide cycle and to view future and past predictions. There is also an option to display the tidal predictions in table form.

The only drawback is that Tide Tool runs on Palm OS mobile phones only. It requires Palm OS version 2.0 or later, which includes any Palm device that shipped after 1997. Download a free version of Tide Tool for your Palm OS device.


Note that for Tide Tool, as well as for other tide and current prediction programs, there are fewer locations for current prediction than the height of the tide. Tide and current predictions are dependent on data collected by NOAA. Unfortunately, funding for the National Current Observation Program has been dramatically cut since the 1980's.

However, you will find that current data does exist for critical locations such as busy canals and channels. For example, any good tide and current prediction program will have predictions for current in important passages such as Hell Gate in New York, Cape Cod Canal in Massachusetts and the C&D Canal in Maryland and Delaware.

Having passed through the Cape Cod Canal one time against the current - and if you are wise, you will do it only once - we learned it is well worth planning our trips to travel with the current, or at the least to go at slack current. The savings in time and fuel, especially at today's prices, can be significant.

Another good example of where knowing the speed and direction of the current is critical is Hell Gate in New York City. With currents that run as fast as 5 knots, not only can you waste fuel and time if you try to run against the current, it can be downright dangerous if you are running with the current and meet one of the many barges coming through the infamous blind S-curve.

The speed and direction of the current can also be critical information when docking. Not only is it important to know the direction, so that you can safely come in against the current, at some docks it can be vital to know the current strength. In areas with extremely fast currents you may want to time your arrival and departure accordingly. cTide cTide is a program for Windows Mobile that provides reliable data from about 5,900 locations, including Boston.

We learned this lesson the hard way the first time we pulled out of a slip in St. Augustine, Florida. The current at our home dock can regularly be 1 or 2 knots, so we felt pretty comfortable docking with the current running. We knew the tides in St. Augustine were a "middling" 5 feet, but we failed to take into account the effect of the nearby ocean inlet. Fortunately, the only damage was a bent anchor when we were forced against a piling.

Having a program readily at hand to check tidal information has become a requirement on the Intracoastal Waterway. We have found that the lack of funding for dredging on the Atlantic ICW has taken a toll. Boaters can no longer depend on 12 feet of controlled depth down its length. For many boats, transiting the Atlantic ICW is an exercise in timing when transiting low areas.

A few years ago, we were in Beaufort, South Carolina hoping to meet friends in Charleston. This is a portion of the ICW we had avoided in the past. Weather predictions were poor offshore and remained so for several days. We decided to see if we could "ride the tide" up the ICW. Using tide predictions, we were able to time our trip by varying our speed to match high tide at 8 different tide stations. We had charts and diagrams indicating the precise timing for the various stations, which were checked off as we progressed. We're pretty sure that less planning went into the last Space Shuttle mission. We were successful, and while it was an interesting exercise and a good test of our tools, we're not too eager to do it again. cTide cTide data for Cape Cod.


cTide is a free, graphical tide prediction program for Windows Mobile. It is also based on XTide and provides predictions for about 5,900 locations around the world. Data can be displayed in a graphical form, and predictions are available on any date between 1970 and 2038. We have found cTide to run slower than Tide Tool but the predictions are reliable and the display is comparable. Download a free copy of cTide.

NavStation Tides is a Windows Mobile program that offers tide predictions for more than 3,000 stations worldwide, using the UK Admiralty Simple Harmonic Method. The software costs about $40 and includes tidal data for two calendar years, with additional years available for a small fee. Tide predictions can be displayed as a table or using a tide plot. Another commercial application is Tide Plotter, which offers a wide variety of display formats including plots, tabular and map-based. Tide Plotter sells for about $25, which includes software versions for your Windows CE, Windows Mobile or Pocket PC mobile phone, as well as your PC.

There are several ways to access tide predictions on your Apple iPhone. tideApp is a web-based tide predictor. iNavX and Navionics include tide and current predictions with their iPhone charting software. ShralpTide is a good free iPhone app. There are several others as well.

To access tide and current predictions on a Blackberry or Symbian mobile phone you will need to go to one of the many available websites. The NOAA website offers a wealth of information including interactive maps, tide plots and text-based tide charts, which you can configure in a variety of ways by selecting the units, time zone and past and future date ranges. It is not formatted for display on mobile phones, so it can be somewhat cumbersome to use.


There are a variety of web-based servers using XTide to serve tide predictions online. One of the most used is a website from the University of South Carolina. The site provides an almost overwhelming number of options for displaying tide and current predictions. The tide table displays fine on a mobile phone. Most of the rest of the website is cumbersome to use. But it's a good option in a pinch. NavStation NavStation Tides is a commercial Windows Mobile program that covers about 3,000 locations.

Others websites include Tidelines Online, which shows a simple 5-day tide plot. The website attempts to reconfigure the data for your mobile phone, but actually makes it harder to view. We found it better on our AT&T Tilt mobile phone to select the "Desktop View" and use the scroll bars to view the table. It is not unusual when displaying websites on a mobile phone browser that you will need to experiment with the various viewing parameters. As you gain experience browsing on your phone, you will learn what works best for you and your device.

Easy Tide offers free 7-day predictions worldwide. If you register on the site you can store your favorite ports, enter notes and view additional notices. For a nominal fee you can access sunrise/sunset data, lunar phases and other enhanced predictions. Though Easy Tide makes no accommodations for your mobile phone, it displays a rather nice tidal plot. You just need patience while scrolling to the proper place on the page.

Some weather sites also include tide predictions. For example, the Weather Channel site offers tide predictions as part of its Marine Forecast.

The website SailFlow offers tidal information in a different style, showing the tide direction and speed with arrows on a map. The arrows point in the direction of the current with the arrow color indicating the strength. You can display an animation of the predictions for the coming 24 hours. We have found this visual presentation useful when navigating up rivers and through bays, such as the Delaware Bay. In addition, the site allows you to view tide predictions in the more traditional tide plot. SailFlow SailFlow is a website that offers tides and current information graphically, with arrows and colors indicating direction and severity.


Another bit of useful information that is included with each of the programs and sites mentioned, with the exception of Tidelines Online, is sunrise/sunset and moonrise/moonset times. The phase of the moon affects the height of the tide, so most tide predictors, such as Tide Tool, cTide and SailFlow, display this information along with the tidal data. The Weather Channel provides it under their "Marine Forecast" section.

Knowing when the sun will rise and set can be helpful for even a simple day trip to ensure a safe, comfortable passage home. We consider it when making our way along the east coast, often planning to leave port at daybreak and choosing our next port so we arrive before dusk. This is especially important if we are traveling to an unfamiliar port.

The moon rise and set, as well as the phase of the moon, become important when planning for an overnight passage. We may choose to wait for better weather if we will be traveling mainly without moonlight, or alter our course to avoid a popular fishing ground. And nothing can help give you a second wind during a night shift than watching for the upcoming moonrise, or better yet, the sunrise.

Tides, currents and sun and moon data are the perfect collection of information for your mobile phone. The simple tide plots and tabular lists tend to display well on the smaller screen. Having free, native applications that run directly on your Windows Mobile, Palm OS, and iPhone devices is convenient and provides fast access. The many different websites provide additional options while also ensuring tide and current predictions for Blackberry and Symbian mobile phones.