Electronic Cartography Update
Ever get confused about the names and types of electronic charts out there, and what runs on what, and where the data comes from? We do, too, so here's a review, and a handy reference guide.
There's a Gary Larson cartoon that shows the homeowner outside the house with a can of paint and a brush in hand, and everything in the picture is drippingly labeled: The House. The Dog. The Tree. The caption says "Now!... That should clear up a few things around here!"
We will endeavor to do the same thing for electronic cartography here, as we do every few months: Recap the basics, touch on what we've covered before, and when, and say what's changed since then. Bear in mind that it's entirely possible, even likely, that what you're reading here will have been updated, expanded, discontinued, renamed, or sold since we wrote it.
We'll skip, just this once, our earnest adjurations about the need to keep paper charts aboard, the need to keep up piloting skills, the need to flip off the GPS once in a while. The fact is that GPS receivers, chartplotters, and computer navigation programs are rapidly becoming the basic (and too often the only) navigation tools for a growing number of sailors. So we'll cut to the chase.
About 25 years ago, when electronic cartography was becoming important for commercial and naval vessels, the major problem lay in the fact that computers of that era were very slow and had very limited memory and storage capacities—and chartplotters were even more limited versions of computers.
While it's not particularly difficult to scan a paper chart—in effect, to take a picture of it—that "picture" contains a great deal of information that takes up a great deal of storage space. This kind of picture is what's referred to as a raster chart. It takes a very large, powerful, expensive chartplotter to handle enough raster charts to cover a reasonably large area. While this might be a feasible approach for a large commercial vessel, it just doesn't work for recreational craft. Cartographers responded by providing vector charts—initially extremely simplified representations of the much bulkier raster charts.
Vector charts were—and still are—much more compact than their raster counterparts. A raster chart may require 100,000 or so bits of information for every square inch of chart, regardless of whether there are any features worth noting in that particular square inch. A vector chart, rather than keeping all that information, stores only the features of interest, and stores them as mathematical descriptions, rather than bit-by-bit representations. A one-inch straight line may require 300 pieces of information on a raster chart, and two or three on a vector chart. The difference is similar to that between an image developed from a painting program on a computer, and one from a CAD program.
As personal computers became faster, with vastly increased memory and storage capacities, raster charts became practical. Raster charts, after all, have some definite advantages. Assuming that they're produced with sufficiently high resolution, they're exactly as accurate as the original paper charts. In fact, Maptech, which has the exclusive contract with the US government to co-produce raster versions of the NOAA charts, works simultanously from the same data layers that go into the paper versions. They are truly the same material in different forms.
The other big maker and seller of raster charts, Softchart, scans the finished charts. They, too, have all the accuracy, but their twist is that they adjust the contrast and color of the charts to make them more vivid and less pastel. The Softchart products work through more software programs than Maptech's, including the NavimaQ program designed for the Macintosh (see below).
Raster charts have a few inherent drawbacks. Since they're copies of paper charts, they come as individual area charts, and, unless there's some programming adjustment, it's all too possible to sail or power your way off the edge of the chart, which can be an inconvenience. One fix for this problem is called "quilting," a process in which the adjoining chart is electronically sized and oriented to act as a continuation of the chart you're leaving. In the past we've encountered losses of accuracy due to the quilting process, but we haven't encountered any recently. Another approach is for the computer to automatically load the adjoining chart, but you can't display the whole cruise on one seamless chart.
Other limitations have to do with zooming. If you zoom too far in on a raster chart, the lines appear thick and fuzzy, and the smooth curves of the chart appear as jagged lines. If you zoom out too far, the high level of detail shown in the chart becomes an almost-unreadable clutter (remember, the details were designed to be read on a chart that's several feet wide, and even a large screen on a laptop is something like reading a chart through the wrong end of a microscope. Still another problem is that if you decide to view your chart rotated so that your projected course is up, rather than with north up, all the text will also change orientation.
Still, raster charts have been used (by the Coast Guard, among others) and are quite serviceable, particularly on longer cruises where you're not doing a lot of flipping between charts.
Experienced navigators like raster charts because they look like the paper charts they're used to, and they are, so to speak, "backed by the full faith and credit" of the government.
While raster charts work well on today's powerful notebook computers, they still aren't feasible for chartplotters. Lacking a PC's hard disk, a chartplotter's storage is limited to what will fit on a plug-in cartridge. While the recent advances in vector cartography have made this limitation much less severe than it used to be, PCs are still about the only hardware in town for pleasure-boaters who want to work with raster charts.
Now, a bit more about vector charts.
The first electronic vector chart was introduced by Navionics in 1985. Shortly after, C-Map introduced the replaceable ROM (Read Only Memory) cartridge, which is still the basic chart storage medium for the chartplotters available to recreational boaters, although there are many variations of the ROM cartridge.
Vector charts have come a long, long way since the crude, oversimplified drawings that appeared on earlier chart plotter screens. Newer charting technologies and the greater storage capabilities of personal computers have resulted in a generation of vector charts that are every bit as detailed as raster charts, and have several advantages over their bit-mapped counterparts. IMO (the International Maritime Organization) has set standards for vector charts, and they're widely used in international commercial shipping.
One advantage of the vector charts is that they're compact, in terms of storage. Detailed charts of the world can now fit on a single CD. More important is the fact that a vector chart can be layered, so that one layer can carry coastal outlines, another can carry depth information, another can contain information on lights and buoys and so on. A navigation program using this type of chart can display only the information that you're interested in at the moment by superimposing the layers you want and suppressing the ones you don't. This feature can go a long way towards reducing clutter and making charts more readable. Raster charts can have layers added, but you can't suppress information that's on the original scanned chart. Vector charts bypass the problem of falling off the edge of the chart: they're easy to make seamless.The significant problem with vector cartography is that datapoints are still largely hand-selected, placed, and corrected. When we say by "hand" we don't mean scribes with electronic pens—much of the process is automatic—but the decisions about what to put in and leave out are still human, and over the years we've seen plenty of mistakes in vector charts. They're getting better all the time, and probably most of the well-traveled waters are properly covered. But just when we start getting complacent about it, we see a zinger. In the August 15 issue, for example, we printed a picture of a vector chart that had a label for Long Island well inland on the Connecticut shore. This doesn't fill you with confidence.
Navionics and C-Map are still the sales leaders in providing electronic charts in cartridge form for chartplotters. More recently, Garmin introduced their proprietary Blue Chart cartridges, based on the extensive Transas chart database.
Transas started out as a Russian company in 1990, aimed at using computer technology for marine, airborne, and land transport technology. Early on, it provided ships of the former USSR merchant fleet with electronic cartography. From this start, Transas went international, supplying cartography databases to much of Europe’s merchant fleets as well as the Swedish Navy and the MIR space station.
In addition to supplying vector chart data to Garmin, for Blue Charts, and to Nobeltec, Transas markets its own PC-based navigation software to run its data. Formerly called Tsunamis, it's now called Transas Navigator.
C-Map cartridges have undergone several levels of upgrade over the years. In 1995 they introduced their C-Map NT cartridges; in 2002 they provided better graphics and faster response with their C-Map NT+ cartridges. Commendably, they made sure that this new line would be able to run on any plotter that could use the older NT format. They’re used by Raymarine, MaxSea, and Global Navigation. C-Map also produces IMO-compliant charts for use on military and commercial fleets.
Navionics' charts, from what we can see, are basically comparable to C-Map's. Navionics, in addition to supplying cartridges for dedicated chart plotters, also provides cartography for PC-based navigation software. Navionics cartography is employed by Swan, PC Plotter, Seatrack and Geonav.
We've found that Garmin's Blue Chart cartridges provide the most detailed, most impressive display we've encountered on a chartplotter. As we've said before, part of this impression could come from a prejudice towards traditional charts on our part, and Blue Charts look most like those.
Garmin offers an interesting approach to purchasing charts: You can purchase the usual pre-loaded cartridges, or you can buy a CD that contains all the charts, and download them yourself from a computer.
The newest entrant in the vector chart derby is, of all things, NOAA. This long-time supplier of paper charts has joined the vector chart ranks with its S-57 series of charts (known as ENC®, for "Electronic Navigational Chart), which correspond exactly with NOAA's paper charts.
When NOAA launched this project, they started out with charts for commercial shipping, which lacked detail, particularly in depth information, for the shallower waters negotiated by recreational boaters. These Version I charts have been supplanted by Version II charts, which contain all the detail of their paper counterparts. They conform to the IMO standard, and best of all, are available for downloading from the Internet at no cost. That's what we said—they're free!
NOAA's intent, they told us, was not to compete with private cartographers, but rather to provide a super-accurate cartography database that individual companies could build on. And while it's true that these charts may not have some of the bells and whistles that can be added to them— superimposed weather data, tides and currents, photographic bottom contours, and the like—they're fine charts to navigate with just as they are. As an added enticement, upgrades and corrections are posted on the Internet as they're made, and can be downloaded as often as is required.
You can view these charts via a no-cost downloadable viewer; there are several of these, including ones from Fugawi, CARIS, dkLook and ESRI ArcView. They can all be found at http://chartmaker.ncd.noaa.gov/mcd/enc/resource.htm.
Merely viewing them doesn't do you much good (apart from satisfying curiosity.) You can't print them, or do any effective cruise planning with them. To make these superb charts useful, you'll need to buy some navigation software. At this point, the best-known navigation software programs that can use the NOAA charts directly are Fugawi and MaxSea. There are sure to be others—The CAP'N, long a staunch supporter of raster charts, has announced that it will have a version compatible with the NOAA S-57 series in the near future, and we're sure that other publishers of electronic charts will use these NOAA charts as a basis for their proprietary charts.
Anything for Mac?
We're mostly speaking here of Windows-based machines, because hardly anyone makes nav software for the Macintosh. MaxSea, which used to make a Mac version of their program, no longer does. The niche seems to be entirely occupied, for the moment, by two small companies. Quintessence Designs makes the NavimaQ 3.04 program, which is recommended for Mac OS9, but will run on OSX when toggled over to the Classic, or OS9 configuration. For information, see www.quintessencedesigns.com.
The other company is called GPSy. The "Pro" version of their software is compatible with nautical charts in rasterformat. Visit www.gpsy.com.
We have not run either of these programs, having had to move from Macs to the Dark Side years ago. Collectively, all the Macs among us now might be able to run a game of Tetris. But with this new G5 machine... Where's Luke Skywalker when you need a rescue?
We'd be glad to hear reports from readers on how either or both of these programs work.
And For the Future...
We're neither smart nor brave enough to venture any detailed predictions about the future of electronic anything. Some general trends, though, appear clear. Personal computers will continue to get more powerful, faster, and less expensive. Chartplotters will, too, but will probably lag far behind in both speed and memory size—there's just not enough of a marine market to pay for the kind of engineering that the general computer market can support. PCs are likely to make further inroads into the dedicated chartplotter market.
Another well-established trend is that of integrated displays. A superimposed view of the chart, radar information, depth soundings, weather and tidal information (tides and currents) is available with some programs now. Adding further layers showing water temperatures and anything else that's measurable should not be a major problem.
Should you wait before buying? As with anything concerning computer equipment, there's never been a better time to buy than right now, or a worse time. Prices keep dropping; capabilities keep increasing. A sound approach is to decide what you need, and buy that.
The most important thing to do with any navigation equipment, whether it's parallel rules or software, is to practice with it and master it, so that you end up spending your energy and concentration on your navigation, not on your navigation tools.
Also With This Article
Click here to view "Chart Software: What Runs on What."
Recent, Related PS Articles:
• Monochrome GPS Plotter-Sounders (August 15, 2003)
(Garmin GPSMAP 188 and 168 Sounders; Lowrance LMS-320DF)
• Color GPS Chartplotters (April 15, 2003)
(Furuno GP 1850W, Navman 5600, Si-Tex Nautilus NT iGPS,
Standard Horizon CP170C, Standard Horizon CP150C)
• Chart Chips (April 15, 2003; sidebar)
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• Maptech Pocket Navigator (February 15, 2003—Chandlery)
• Electronic Charting Evolution (October 15, 2002—Riprap)
• Navigation Software Update (August 1, 2002)
(Raymarine Raytech Navigator, Maptech Offshore Navigator, Fugawi)
• Navigation Software (February 1, 2002)
(CAP'N First Mate, CAP'N Voyager, MaxSea Navigator, Nobeltec VNS)