How to Keep Your Chart Data Up To Date

Top of the Charts

There are numerous ways to keep your chart data up to date.

Finding your way through shifting banks or a channel such as this one demands the very latest information.

No one who has gone back to their hometown after a few years away can fail to notice how much things have changed. Maybe a new store has opened or an old one closed; there may be new houses or new roads; and while familiar landmarks may have been demolished or changed beyond all recognition, it is quite likely that new ones will have appeared.

Much the same happens at sea, but there we are much more dependent on charts than we are on maps and landmarks. For one thing, the risk is greater. Relying on a buoy that has been moved or trying to go over a shoal that is shallower than it is shown on the chart could be far more serious than turning down the wrong street. Fortunately, there are plenty of systems in place to help us keep our charts up to date.


Local Notices to Mariners (LNMs) are the definitive source of official government data. Each U. S. Coast Guard district constantly collects information from Coast Guard vessels, the National Oceanographic and Atmospheric Administration (NOAA) and National Ocean Service, naval and merchant ships, and yes, even recreational vessels and members of the public and collates all of it into LNMs. Then every week, the Coast Guard Navigation Center publishes the latest LNMs on its Web site, along with changes to individual charts, which are listed as Chart Corrections.

Each Chart Correction gives the number of the chart affected; an instruction to add, delete, change, or relocate; followed by a description of the feature affected and its position. It’s all very straightforward: You just have to write or draw the change onto the chart. Perfectionists might choose a drawing pen loaded with magenta ink, but a blue or black ballpoint is a good substitute. Don’t be tempted to use red, though: It is almost impossible to see in dim red light!

The notices for a single Coast Guard Region can run to several thousand pages per year, so the biggest challenge with LTMs is wading through the notices to find the ones that affect you. A more convenient alternative, particularly for those with only a handful of charts, may be to use the Office of Coast Survey Web site, which allows you to key in the number of a particular chart or the name of the harbor, and almost instantly receive a summary of every chart correction that has affected that chart or harbor since it was published.


Even when you buy a brand-new paper chart, it may already be out of date. For example, a note in the margin might tell you that it is “corrected through LNM Oct 12/10,” but it cannot tell you how many corrections are already waiting to be applied to it. One solution to this, and to the sheer tedium of applying hundreds of apparently insignificant corrections by hand, is to buy Print on Demand (POD) charts.

The name sums them up. Instead of being printed once a year (or every few years) and held in stock, POD charts are printed to order by NOAAs commercial partner OceanGrafix and shipped by FedEx. As well as being more up to date than a printed chart could possibly be, they are clearer and more durable than regular charts, and at $27 for a water-resistant paper chart, they are close enough in price to be an irresistible alternative.


Electronic charts go out of date just like paper ones, but of course you can’t correct them with a ballpoint pen. Some of the very sophisticated systems used on commercial and military vessels allow weekly updates with individual pieces of a chart—downloaded by satellite, if necessary–automatically “pasted” on top of the out-of-date information. For recreational boaters, however, it is much more common (and far more practical) to replace the entire chart card.

Different companies have different update and pricing policies. NOAA is by far the most generous, with brand-new raster and vector charts, updated weekly, available free of charge from its Web site. Unfortunately, their charts can be used only by the minority of boaters who use PC-based charting systems.

Those of us who use dedicated plotters or multifunctional displays are in the hands of our cartography suppliers. Jeppesen (C-Map) updates its chart database three times per year and offers one free new-for-old exchange each year to anyone who has paid the $89 subscription to become a member of Club Jeppesen.

Garmin aims to update its Bluecharts twice a year and offers a 50-percent discount on the list price of the latest card to anyone who sends in an out-of-date card—even if it is of a different area—as long as they registered with the company before sending it.

Navionics is in the process of changing its update system. At the moment they offer a cash-back deal in which they refund approximately 25 percent of the purchase price of a new chart (up to $100) if you send the old one back. That, however, is about to be scrapped. Final details of the new system are not yet available, but the principle is that anyone with a Navionics chart dated 2011 or later will be able to download as many updates as he wishes, free of charge, for one year.

The NOAA-based Mapmedia charts used by Furuno are updated two or three times a year and are available free of charge.

  • Local Notices to Mariners
  • POD charts
  • NOAA Raster Chart
  • NOAA Vector Chart
  • Jeppesen C-Map
  • Garmin Bluechart
  • Navionics
  • This article originally appeared in the February 2011 issue of Power & Motoryacht magazine.

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