Digital Maps - Appalachian Mountain Club

Digital Maps

May 1, 2009

I’m a map junkie, always looking for my next cartograph­ic fix. To me, maps are more than just drawings—they’re adventures waiting to happen, gateways to exciting new worlds. And for backcountry travel, I crave the best topograph­ic maps I can get.

The U.S. Geological Survey publishes topos for the con­tiguous U.S. at a scale of 1:24,000, the most detailed versions available. Fifteen years ago, a serious map addict needed to pur­chase more than 1,200 of these for complete coverage of New England (or roughly 3,400 for the entire Northeast). At the cur­rent rate of $6 a pop, that’s $7,200-$20,000—an expensive habit! Forget that. To feed my need these days, I buy the goods in digital format and score all of New England for $100 or less.

A variety of companies sell topos in electronic form, mak­ing it easier than ever to plan a trip, print the requisite maps, and send essential coordinates to a GPS unit. But these magic maps still don’t satisfy all my needs, especially when it comes to obtaining up-to-date trail information. So what’s the best way to get a quality fix?

RASTER MASTER  National Geographic has scanned USGS topo maps for the entire country and seamlessly stitched them together to produce their TOPO! software packages ($100 for all of New England, New York, Pennsylvania, or the mid-Atlantic region). It’s a savvy business model. USGS maps and data are in the public domain—anybody can use the information at no cost. National Geographic enhances this with a set of simple, user-friendly software tools that allow you to draw trails, measure distance, or print a map of any size, among other things. These types of maps are known as digital raster graphics (DRGs), scanned images that have been georeferenced to contain coordinate data for every point on the map. MapTech also uses DRGs in its Terrain Navigator software, a pricier option ($300 per state or region) that in­cludes a few more features for the advanced user.

The average age of a USGS topographic map is more than 25 years.

VECTOR DIRECTOR  Other companies, such as DeLorme and Garmin, use a different technology. Their topos are vec­tor maps, which store each topographic contour as an indi­vidual line rather than saving a pre-existing map as a digital image. This considerably reduces the file size. Vector maps for the entire U.S. can be contained on a single CD, but they do not contain the level of detail found on USGS maps, often leaving out smaller landscape features, such as springs or old logging roads. They are also at a smaller scale, equivalent to roughly 1:100,000. The big advantage is that you get broad coverage at little cost; DeLorme’s Topo USA software cov­ers the entire country for $100 (or the eastern U.S. for $50). Garmin’s MapSource software ($100) covers all 50 states as well, but is the most primitive of the bunch; a monopolistic tie-in with its GPS units drives sales instead.  

THE GPS MESS  Most of today’s GPS units contain enough memory to support detailed maps. Unfortunately, most units only accept maps from the manufacturer’s propriety software. Garmin’s MapSource software is perhaps the best known ex­ample, though both DeLorme, Magellan, and other manu­facturers have followed suit in the past. Keep in mind that most topo software will allow you to upload or download basic coordinate infor­mation to and from a GPS—just not the maps themselves.

LOCAL KNOWLEDGE  The biggest drawback of topographic software is its lack of up-to-date trail information. Paths change, disappear, or get re-routed. Campgrounds and backcountry fa­cilities come and go. USGS information is updated infrequently, a fact reflected in most topographic software. As a general (nearly universal) rule, a current up-to-date trail map for a given area will be far more accurate than any electronic map based on USGS data—at least when it comes to trail locations. USGS maps still come out on top, however, in areas where you want maximum detail for off-trail navigation. Feed your needs appropriately.

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Matt Heid

Equipped blogger Matt Heid is AMC's gear guru: He loves gear and he loves using it in the field. While researching several guidebooks, including AMC's Best Backpacking in New England, he has hiked thousands of miles across New England, California, and Alaska, among other wilderness destinations. He also cycles, climbs, and surfs.