Chartplotters Alone Are Not Enough

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Two views of the harbor and neck in Marblehead, Massachusetts: the view at left is a screen grab from an ENC chart; the view at right is screen grab from a raster chart, the same electronic chart type used in the creation of printed charts, and which is no longer going to be updated by the National Oceanic and Atmospheric Administration (NOAA)

Two views of the harbor and neck in Marblehead, Massachusetts: the view at left is a screen grab from an ENC chart; the view at right is screen grab from a raster chart, the same electronic chart type used in the creation of printed charts, and which is no longer going to be updated by the National Oceanic and Atmospheric Administration (NOAA)

Is the paper chart going the way of the dodo bird? NOAA is ready to scrap them. Costs too much they say. They no longer print them, although they do still create the necessary digital files. So, who is affected, and why?

Electronic Navigational Charting (ENC) is king. ENC is based on a vector chart format accepted by commercial shipping worldwide, so that makes sense. Or does it? First, consider that there are thousands of commercial ship navigators, and shipping is a major industry. However, there are millions of recreational boaters. We should be supported, too.

Some say almost everyone is using electronic chartplotting anyway, so paper isn’t really needed. Wrong! This belief draws its inspiration from the demise of the gas station road map. Cars, though, are different from boats. They follow defined roads. That gadget in your car will get you where you want to go by telling you where to turn at each intersection. But the water is different—no roads.

Beyond that my biggest issue is big picture versus small. Your chartplotter is but a narrow window to the world. On most boats, a 10in diagonal screen is large, 5in to 7in more like it. How much chart can you fit on that screen? I contend the smallest scale that is practical for coastal navigation is 1:80,000. (Small scale means large area.) At that scale, 1in represents about 1.1 nautical miles, so from the center of your chartplotter you can only see a few miles unless you scale out, at which point you can’t see details. You are therefore faced with a dilemma. You can see where you are, but not where you are going. Or you see where you are going, but not what’s there.

Compounding the problem is the fact that as you scale in and out, the software is changing what you see in accordance with its algorithms. Features can appear and disappear unexpectedly—like the reef the VO65 Team Vestus ran up on at full speed in the 2014-15 Volvo Ocean Race. The solution then is to use a chartplotter and a paper chart (or chart book), especially if you are venturing into unfamiliar waters.

Now, back to those commercial mariners. Those that cross oceans don’t have much to worry about when they’re far from land, and as soon as they approach port, they typically hand over control to a local pilot whose job it is to know its waters like the back of their hand. Similarly, commercial mariners working coastal typically travel the same waters over and over again, and therefore know the way. They generally also have quite large, or even multiple electronic displays at their disposal.

What recreational boaters need, on the other hand, is as much local-waters information as they can get, especially when visiting someplace new. They also often go places commercial folks do not.

At the heart of the problem lies the fact that the raster digital files used to create paper charts—as well as the electronic charts that still look like paper—are totally different from the vector files used to create ENCs. The two not only “look” very different on screen, they are also manifestly not interchangeable in terms of their basic coding/algorithms.

If going forward, NOAA focuses on the needs of commercial mariners to the point where it only updates ENCs and does nothing to keep its raster, and by extension, paper charts current, many, if not all, local details will eventually fade away leaving paper and raster charts hopelessly unreliable and ultimately, useless. What is needed is a means of efficiently updating paper charts with ENC data without eliminating the paper (or raster) charts needed by those of us who go where the big ships do not.

Never forget, at some point the various electronic gadgets you have on board will either fail or at the very least become suspect: more likely than not at the exact moment you need them most. Blame a guy named Murphy. When that happens, you will not only want a paper chart, but one that is up to date and accurate! 

Bob Sweet, is a Senior Navigator and author of numerous books, including The Weekend Navigator, GPS for Mariners and the “Quick Guide” Using GPS, among others. He is also a consultant and a former National Educational Officer, U.S. Power Squadrons. He lives on Cape Cod

June 2020



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