Wherever You Go, There You Are

A guide to GPS and the technical frontier of navigation

Apr 1, 2000
Outside Magazine
Bob Graham is a man possessed. Still blonde, wiry, and boyish at 58, this retired Courtland, California, farmer-turned-mountaineer has spent the past five years roaming the Sierra Nevada in an attempt to retrace the 122-mile-long route taken by John C. Frémont in 1844, when the brave but vainglorious lieutenant, along with Kit Carson and a detail from the U.S. Army Corps of Engineers, made the first known winter crossing of the northern half of the range. In his own travels, Graham has seen his car battery explode due to high altitude and been menaced by a mountain lion. But he's never lost sight of his key obsession: How did a half-frozen, wandering adventurer like Frémont find his way through a forbidding alpine maze?

One snowy morning last spring, Graham let me tag along on a hike to one of the explorer's campsites, a spot near Carson Pass he'd recently discovered. As walks in the woods go, it was both geographically and intellectually rigorous, with Graham delivering a lecture on the technological advances that have eased the burdens of land navigation. To emphasize his point, he explained that Frémont's duties as leader of a U.S. government–sponsored survey expedition included having to call a halt at midday and get up at odd hours of the night, weather permitting, to futz with a bunch of sextants, chronometers, thermometers, telescopes, astronomical tables, and complex mathematical formulae, and thus determine the latitude, longitude, and altitude of his exploring party.

Fast-forward a century and a half. As we snowshoed up a spur ridge covered in aspens and lodgepole pines, Graham suddenly stopped, reached into his parka pocket, and extracted his cell phone–size Magellan 315 Global Positioning System receiver.

"What if Frémont had had this?" he barked. Well, maybe his men wouldn't have had to eat their boots. Alas, this was not the answer Graham was looking for.

"He wouldn't have had to get up in the middle of the night, waiting to fix one of the Jovan moons," he said. "At any moment of the day or night he would've known where he was."

Then he punched a button. In seconds, our position materialized on the tiny screen: Latitude 38š 41' 56" N; Longitude 119š 57' 35" W; Altitude 7,776 feet. So much for Jovan moons.


The GPS relies on a constellation of 24 orbiting satellites that the United States Department of Defense began launching in 1978 to meet its own navigational needs, and to keep tabs on military movements during the Cold War. Using atomic clocks accurate to within one second every 70,000 years, each satellite continuously broadcasts the time and its position. A GPS receiver, pulling in signals from three or more satellites simultaneously, then measures how long it takes them to arrive, calculates the distance to each orbiting body, and, using simple geometry, produces a fix on your position.

First made available to the public in the 1980s, GPS technology nowadays is exploited by everybody from bush pilots to mountaineers to your Uncle Milt the bass fisherman. Instead of having to lug around a load of obscure, weighty, and hard-to-figure-out navigational equipment (would you know where to buy a sextant these days?), now you can push a button or two on your GPS receiver and, just like that, you're on the map. Most models can store at least 200 "waypoints," readings on locations you either want to go to or have been to already. If you haven't been there, keystroke the coordinates and your GPS will help you find the spot; if you're already there, just press a button to bookmark the position. By entering a series of waypoints, you can create a route and store the whole thing for later use.

In his hunt for Frémont's trail, Graham typically studies a topographical map to suss out the coordinates of a particular Sierra locale he wants to visit, and then keys them in to his GPS. Using the same map, he finds a road that takes him within striking distance, parks, and switches on his GPS to take a reading on his location. At this point the instrument can tell him exactly how far his target is and in what direction. Now it's just a matter of using a compass to hike to the site. That's right—a compass. As the amateur cartographer is quick to point out, while GPS would have greatly reduced Frémont's logistical burdens, it would not have solved the mess he got himself into. "Since Frémont didn't have a decent map of the Sierra to use GPS by, the system would have told him where he was, but not where he had to go—or anything about terrain," Graham says. "The Sierra still would have been terra incognita for him."


When it comes to terra incognita, Graham knows what he's talking about. Because merely pinpointing your position won't get you anywhere, you need to own traditional orienteering skills along with that fancy GPS. To fully exploit the data it provides, you should know how to use a topographical map, a compass, and a plotting scale—a rulerlike tool calibrated to the same scale and coordinate system as your map.

And then there's the small matter of UTM. All GPS receivers provide traditional latitude-longitude readings but, increasingly, many also utilize the newer Universal Transverse Mercator (UTM) coordinate system. Universal Transverse whaaaa, you ask? Good question. Lines of longitude and latitude superimposed on the earth's spherical surface result in inconstant distance factors, meaning a degree of longitude at the equator is about 69 miles long, whereas it's about 49 miles long at Minneapolis, on the 45th parallel. By "flattening" the earth's nonpolar regions into a rectangle and dividing them into 60 zones, UTM reduces those inconsistencies.

Both systems work, it's just a matter of personal preference. In Graham's case, he sticks with traditional latitude-longitude readings. "Most of the time, I'm working with 19th-century maps and Frémont's journals, which don't use UTM," he says. For the rest of you modern-day frontiersmen out there, now may be the time to get acquainted with both systems, lest you find yourself using your shiny new GPS device as a projectile to fend off vultures.

If most of this sounds like a techno-geek soliloquy left out of the latest Star Trek flick, here are a couple of pre-Computer Age caveats. First, although GPS receivers feature tiny video screens that display preprogrammed map grids with various zoom options, those images don't compare in detail and scope with traditional paper topo maps—so definitely use both. Second, while GPS offers bankable latitude and longitude coordinates, its altitude readings are often unreliable (see "Going Up?", a review of altimeters, page 130).

Ultimately, Graham is pretty sure he would have found the Frémont campsite using the old maps-and-legends method, but GPS made success a speedy certainty. "Without GPS," he says, "even after getting close to the site, it would have been hours of wandering here and there." Which is fine if you're basking in nature's splendors, but not so good if your men are starting to gaze longingly at your footwear.


Garmin GPS 12MAP
Kitted out with a welded, waterproof case, the Garmin 12MAP ($425; 913-397-8200) allows you to download topographic information from a separate MapSource CD-ROM ($152), so you'll know when your trail will rise to meet you.

Lowrance GlobalMap 100
The GlobalMap 100's ($199; 800-324-1356) high-contrast screen is easy to read in daylight, so the map details downloaded from the accessory CD-ROM ($129) come out clearer than your path through the woods.

Magellan GPS 300
Small and lightweight, the rubber-encased Magellan 300 ($100; 909-394-5000) is suited for the space-challenged backpacker, and its intuitive operating system and low price make it attractive to weekend campers, too. —JOHN BRANIGIN

Tom Chaffin teaches U.S. history at Emory University and is currently working on a biography of John C. Frémont.

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