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Raster Charts: the New Paper Charts

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It’s true that I don’t navigate on paper charts anymore, but I appreciate them and I use their electronic equivalent—raster charts, which are basically an electronic scan of the paper originals—more than ever.

One reason for this is what I learned last January while preparing for a seminar called “Soup to Nuts Navigation.” The other reason is the run I made last spring up from North Carolina—including the entire New Jersey ICW, which can’t fit much more boat than Gizmo—with just about every chart type and brand in view. Bottom line: I think we would have had some trouble if my mate and I hadn’t originally learned to navigate with paper charts, and we referenced their raster equivalents heavily.

I have many examples of how a vector chart—a base of geo-positioned data that is assembled into a cartographic image on the fly as you work with your plotter—sometimes fails to convey important navigational information as clearly as paper charts. In this column, I will focus on New York’s Northport power-plant stacks, pictured above, which may well be the most prominent nav aid on the whole East Coast.

Although not an official nav aid, the stacks are 610ft high, well lit at night and absolutely unmistakable. However, to be useful, a non-official mark like the stacks has to be charted. In this case, it should also be on a large-area (small scale) chart because it can be seen from great distances (over 40 miles).

As you can see on the 1:80,000 scale Western Long Island Sound chart (above) the NOAA cartographer did a pretty nice job. The inset also tells the story of how efficiently he or she used a very small section of paper. “North Stack 610” implies that there are more than one of these giants—so now you can confirm the chart position of what you’re seeing from afar—and the clean target symbol gives you a precise spot to lay down a bearing.

So how did that useful information get translated into vector charts? Badly! And it was translated badly by every vector chart-maker, including NOAA. The screen shown above is from a Garmin 8212 plotter showing BlueChart g2 Vision cartography set to the “Normal” level of detail. I started at a zoom level roughly equivalent to the 1:80,000 paper chart and zoomed all the way into the level shown without seeing any sign of the stacks. It was only at the next zoom level in—shown in the inset—that they appeared. Worse yet, if you didn’t already know that this major landmark is just east of Northport, New York, you’d have a hard time finding it on the chart!

The story was nearly the same on the Raymarine gS12. In the Raymarine screen shot shown above, Navionics+ is shown below and Ray’s own Lighthouse vector (derived from NOAA ENCs) also below. Each chart was set to normal viewing mode. I then zoomed in until I could make out the symbols representing the four big stacks. Note how you can drill down for data that can’t be presented well on the chart graphic: in this case, the Navionics software clearly details one of the stacks based on NOAA info. It’s also important to be aware that Raymarine offers free NOAA raster charts, and the company’s chart store offers a growing number of choices for raster charts outside the United States.

Continuing on, the images from my Simrad NSS16 evo2, shown at the top of the facing page (with Jeppesen C-map Max-N+ on the left and Navico’s own Insight chart on the right), once again show both maps zoomed into where I could clearly make out the stacks. In the case of the Insight view, the four target symbols did start to look like something significant a couple of zoom levels out. Note how I put the C-Map in “Head Up” orientation to show how well vector charts do this—the numbers and text stay right side up. I was surprised to see the height of a “Visually conspicuous chimney” listed as just 185.93, with no units specified. It should be in feet, as I’ve set the NSS16 to that measure, or at least it should say meters if it can’t make the conversion.

Fortunately, even outside the United States, the new C-map Max-N+ 2015 will have a complete raster chart layer, very similar to the C-Map 4D Max+ chart packages now available for Raymarine plotters (plus some Standard Horizon and Humminbird models). Better still, the N+ rasters will be “dynamic,” which means that vector-style nav aid data can be drilled into from the raster layer. Sounds good to me!

Finally, there’s the Furuno TZT. In the image seen above I have it showing NOAA-based raster charts in two windows. Furuno pioneered raster/paper charts on its first NavNet 3D system way back when and still does it very well. In this instance, I have again put the lefthand chart window in “head up” mode to illustrate the challenges raster charts face in this respect. I confess I wasn’t pleased with the big jump in chart scale I experienced as I zoomed in, but that’s a NOAA oddity that may be part of the problem all the vector chart makers had with the stacks. Specifically, there is 1:40,000 and 1:80,000 scale chart coverage for most of the United States, but in this part of Long Island Sound the jump is to 1:20,000.

It was heartening to see that NV Charts (the bottom of the three images above) came up with its own conspicuous symbol and “4 Chimney conspic” text to identify the stacks on the 1:100,000 scale page of its chart book (which includes a CD of matching raster charts and an app I’ve tested). Even better are the line drawings of the major lighthouses in the area, a sharp old-time cartography aid that I’m not sure NOAA ever got around to. It’s nice to have help with visual confirmation when you come across marks like this, especially in the fog, even if your GPS is already showing you right where you are.

But GPS could fail, right? Actually, it hardly ever does, which is probably the main reason all those vector charts can be so poor at charting a major landmark like the Northport Stacks without anyone complaining much. Admittedly, vector charting has only been around for about 30 years—while paper (or sheepskin) cartography has nearly a millennium under its belt—but still, I want better.

Editor’s Note: For more of Ben Ellison’s insights on marine electronics, go to panbo.com

October 2015

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