Safe Navigation in Poorly Charted Waters

Posted by Darrell Nicholson at 05:19AM - Comments: (3)

Both printed and digital charts proved inaccurate in several places during our five-day cruise in Southwest Florida.

I often worry that the topic of chart accuracy, which we revisit in the upcoming April issue of Practical Sailor, downplays the importance of other skills, published sources, and equipment we should use to solve a navigational puzzle. A recent bottom-scraping cruise I took along the ever-changing coast of Southwest Florida reiterated some key points regarding coastal navigation.

1. Printed charts have much to offer over digital, especially when planning routes, or making significant routing changes. At the very minimum, a printed small-scale planning chart for the area you are sailing should supplement your digital portfolio. As anyone with a chart-plotter knows, zooming out to planning scale on a vector chart often results in key obstructions disappearing from view, making it too easy to lay a course that intersects with known hazards. This is exactly the type of oversight that led to the grounding of Vestas Wind. Detailed, large scale printed charts of your destination, and of key "emergency" ports along your route can greatly reduce stress when Murphy's Law takes hold.

2. U.S. Coast Pilots, their foreign equivalents, and updated cruising guides can save a lot of headaches, especially when making final approaches to gunk holes that neither printed nor digital charts have portrayed accurately. Two inlets we used during our short cruise were clearly mischarted, as shifting sands had not only reoriented the charted channel position, but also made the fixed navigational aids misleading.

3. Seek out reliable local knowledge. Local professionals, the U.S. Coast Guard, and online resources like Active Captain can be an important source of information when navigating areas that are known for shifting shoals. In most popular ports, tow boat operators and local marina operators are standing by on VHF to help guide sailors around known dangers that are not on charts, but even these sources should be cross-checked whenever possible. Ideally, your sources should be knowledgeable owners of boats with a similar draft to your own.

4. Use your senses. As much as possible, the navigator should try to time challenging navigation when natural forces are in working in his or her favor. A rising tide, good visibility, relatively calm water, and plenty of sunlight at your back can turn a tricky cut into Easy Street. Favoring the windward sides of narrow, shallow channels means that if you do go aground, there is less risk that youíll be driven further into shoal water, and it will be easier to extricate yourself.

5. Dial in your electronics. Depth and radar alarms can be an extremely useful asset in scenarios where the bottom contours are prone to shifting, or where some features are poorly charted. They can be even more helpful if youíve optimized the settings. For example, a deeper than normal sonar alarm setting can alert you sooner when you are creeping toward the shallow side of a channel with sloping sides. Properly adjusted, todayís hi-definition radar can pick up fish traps as well as channel markers.

6. Approach with caution. Fortunately, much of the sea bottom in popular cruising areas are sand or mud and most cruising boats can take an Intracoastal Waterway soft-grounding without harm. So long as you use a slow speed, backing or kedging off can be a simple operation. Of course, the stakes are much higher in many places, making a cautious approach even more advisable.

7. Have an exit strategy or alternative anchorage. Donít be so rigidly fixed to your cruising plans as to put your boat and crew at risk. Try to anticipate any challenges an upcoming obstacle might present and discuss in advance with your crew what will be expected if you suddenly find that seven-foot channel depth is reading five feet on your sounder.

In the debate over paper versus digital charts, it is easy to forget that the most important navigational element on board is neither your chart or your plotter, but the captain and crew. Making sound decisions requires having good information, and as the navigatorís rule asserts, you should never rely solely on a single source for that information.

Comments (3)

"Sound" advice Darrell!! Thanks for summarizing the principles of safe navigation. I have been sailing for 30 years on the West Coast + eight years in the Navy + Caribbean + Panama to Tahiti via Galapagos in 2013 but will still print your article and put it on my boat for any student of navigation to learn from.

Posted by: Canadian Boater | March 13, 2016 2:46 PM    Report this comment

I once had a chart book where the long/lat numbers on the side were accidentally transposed 5 minutes. They recalled them quickly. Fortunately it was a familiar area and only cause amusement. It was only the one page.

The GPS app on my tablet transposed other numbers from the paper charts (boxed nav notes) as depths. Generally obvious.

There are many areas around the Delmarva coast where charts are really no more than a suggestions, with 40-year old data on very mobile sands. The Coast Guard is pretty good about moving the markers, but you best nav tools will always be your sounder and eyes on the water. If it feels wrong, slow down and consider making a 180 and trying again.

Posted by: Drew Frye | March 12, 2016 10:00 AM    Report this comment

We motor (sailed) down the ICW from Buzzards Bay ( Fairhaven, Ma) to Ft Lauderdale ( a few sections outside), and found that Paper Charts, Garmin Chartplotter at the Helm and Garmin Bluecharts on my 1st mates PC, we're not always sufficient!
Active Captain ( overplayed on the Bluecharts) played a significant role in assisting us to avoid shallows, newly formed sandbars, channel obstacles, channel deviations, missing or improperly located channel markers. In addition, a valued tool in searching marinas, anchorage areas, etc.
Adrien and Nina Rock
"Dolphin", Brewer 12.8 Cutter Cruiser

Posted by: RockA | March 9, 2016 7:19 PM    Report this comment

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