June 13, 2002
G.P.S. in the Hand: Worth It in the Bush?

June 13, 2002

WHEN you are hiking, there is something nice about being away from the buzz of technology, enjoying the outdoors without having any superfluous equipment get in the way.

But there is always a moment during the trek when you need to head to the campsite or the next checkpoint, or back to the car. That might be the time for someone — or something — to point you in the right direction.

The latest Global Positioning System hand-held devices propose to make finding your way home effortless. G.P.S. devices use timing signals from a network of 24 satellites to calculate the user's latitude, longitude and altitude and to provide information on how to get to where you want to be.

Restrictions on the accuracy of consumer G.P.S. devices were lifted by the Defense Department, which operates the system, two years ago. As a result, the accuracy of consumer models improved from 330 feet to 30 feet under the best operating conditions.

The newest G.P.S. hand-held devices can receive signals from the Wide Area Augmentation System, or WAAS, a ground- and space-based system designed for airplane guidance. WAAS signals improve accuracy to within 15 feet.

Navigation companies are now tailoring lightweight hand-held devices to the growing outdoor recreational market. I took four top-of-the-line models to the backwoods of Long Island to do a little experimenting. (Though many of the devices I tested are also intended for city navigation, G.P.S. signals are weak and are easily blocked by large buildings and other obstructions — even car roofs and tinted windows.)

All four — the Garmin GPSMap 76S, Brunton's Multi-Navigation System (MNS), Magellan's Meridian Platinum and Lowrance's iFinder Plus — are designed for a range of outdoor activities, including hiking, camping, biking and mountaineering. Models loaded with marine navigation aids can also be used for fishing and boating.

Most top-end G.P.S. hand-held devices have mapping, which allows you to view road and topographical maps while navigating. Using an on-screen map, for example, you can locate your position and follow your progress by marking waypoints. Such a mapping unit will not only guide you during the hike but also give you driving directions to the trailhead from your front door.

I found the Garmin GPS MAP 76S ($449) to be the most advanced of the units I tested. Waterproof and buoyant, it has a barometric altimeter to indicate weather trends and record highest and lowest elevation. It also comes with a basic road map of North and South America, including major highways, rivers, lakes, cities and borders.

You can get more map data by hooking the G.P.S. device up to a PC and downloading the contents of one of Garmin's CD-ROM's. Because road maps lack the detail necessary for outdoor use, hikers will probably want the MapSource U.S. TOPO map, which is similar to United States Geological Survey topographic paper maps and shows detailed geographic features like elevation contours, as well as hiking trails and campgrounds.

The 76S was quick in attaining its position — after I turned it on, the unit took less than a minute to acquire satellite signals and give a reading. (G.P.S. devices need contact with at least three satellites to provide the latitude and longitude of your position; at least four satellites are required for a reading that includes altitude.)

Even with all its features, the 76S is easy to use, with buttons that are clearly labeled and functions that are self-explanatory. (When I tested it, Garmin was still writing the manual, but I was able to figure most things out myself.)

With each of the four devices, I marked the same "home" waypoint and wandered a mile. Although it is WAAS-enabled, the 76S never really got me back to the exact spot where I began. And while its arrival alarms rang when I approached the location — a very helpful feature — the unit's "distance to location" reading then fluctuated around 30 feet, even when I was standing at the original starting point.

I encountered the same accuracy problem with the Magellan Meridian Platinum ($400) and the Lowrance iFinder Plus ($429), which are also WAAS-enabled. When I asked about this, Sidney London at Magellan's technical support told me that the WAAS system has not yet been completed by the government. (Lowrance also explains this in its instruction manual.) The few WAAS satellites that have been deployed are in a fixed orbit around the equator and appear close to the horizon in North America, making it difficult for ground receivers to acquire the signals if there are trees or high terrain nearby. Mr. London recommended leaving the unit in place for two to five minutes for the unit to average the location and gain a more accurate fix before setting a waypoint.

Of all the models I tested, I found the Brunton Multi-Navigation System ($359) to be the most accurate, even without any flashy on-screen maps. It consistently returned me to the exact spot where I had marked a waypoint. The easy-to-use buttons are identified by icon (the instruction manual chart is very helpful). Though the MNS does not display maps itself, it is compatible with topographical mapping software offered by National Geographic or Delorme; you can download data from the G.P.S. unit and chart your course over time on a PC.

Like the Garmin, the MNS has an altimeter that relies on atmospheric pressure, not satellite signals, for its readings. The built-in compass is magnetic and also works independently of the G.P.S. Unlike G.P.S. devices with electronic compasses, the magnetic compass still works even if the unit is not receiving satellite signals, and it can also take bearings when the unit is off (to save battery life). The MNS comes with a storm-watching barometer that gives 12-hour weather forecasts, excellent for extended camping trips. Brunton also offers the nifty SolarPort accessory ($95), a compact solar panel that can recharge the G.P.S. device as well as cellphones and other small electronics. The SolarPort generates 2.2 watts of power, which is not a lot, but it can maintain two fully charged rechargeable AA batteries; two SolarPorts can power the MNS without batteries.
Like the Garmin 76S, the Magellan Meridian Platinum has easy-to-read buttons and a built-in expandable map database; you can add detailed topographic maps with MapSend CD-ROM's via a PC. Waterproof and floatable, the Platinum can also show vertical profile graphs of your elevation changes.

The Lowrance iFinder Plus lost its position most frequently, and I often had to walk around to reacquire satellite contact. For the best accuracy, the unit needs to be moving — it relies on your speed to determine your direction of travel. The iFinder's real strength is as a full mapping unit; the Plus version comes with hardware and software to create customized maps on a memory card. (Other models in the iFinder line come loaded with road maps or coastal navigation aids.) And it is versatile: it can be used for marine navigation, inland road travel or camping, depending on the memory card you insert.

I also tested two entry-level models, the Garmin eTrex ($145) and the Magellan GPS 310 ($120); but after using the higher-end devices, I was skeptical of trusting either of the less expensive models. The new Magellan SporTrak Pro ($269) is a good compromise if you don't want to spend a lot and you want an accurate, easy-to-use device with top-of-the-line features.

Of course, for many hikers, there is no substitute for a good topographical map and an old-fashioned magnetic compass. Experts advise, in fact, that you always bring maps and a compass along, because they never run out of power. But as long as you keep a spare set of batteries in your pack, a hand-held G.P.S. unit will make it hard to get lost.