Those who gravitate to outdoor activities often tend to exaggerate their outdoor exploits—whether that means the number of miles hiked with a heavy pack, the vertical mountain ascent climbed, or the number of miles paddled down a river. Many of those same people (well, men in particular) also have an unadulterated hankering for any new gadget that hits the streets. The much-coveted handheld GPS receiver—a modern marvel that combines the aforementioned passions for the outdoors and gadgetry—can actually be a recipe for true angst.
Why? Because once you buy one of these GPS devices and become proficient in its use, you must get rid of the evidence before you can embellish or exaggerate your exploits. So if you're prone to this sort of behavior, a GPS device will keep you honest.
In A Nutshell: How GPS Works
To get the absolute basics out of the way, GPS, in case you aren't already familiar with it, stands for Global Positioning System. In the simplest terms, GPS is a means of determining your position anywhere on the planet by precisely measuring the distance from your location on the earth's surface to satellites orbiting Earth. Actually, GPS receivers do all the calculations. If you stand out in the open with an unobstructed view of the sky and one of these GPS devices, a receiver can intercept signals from a system of 24 satellites orbiting the earth about 12,000 miles overhead.
The GPS system was launched by the U.S. Department of Defense and became fully operational in 1995. A great deal of the system's accuracy is based on timing. Each satellite has an on-board atomic clock that is accurate to within 1 second every 70,000 years.
All of the devices in this story require signals from three of the satellites to determine an accurate two-dimensional position, also known as a fix. With signals from four satellites, a GPS device can also measure your elevation, providing your position in 3-D.
Of course, there's a lot more information about how various GPS-related technologies work, but this level of detail goes beyond the scope of this story. Suffice it to say that all the products in this story work in very similar fashion.
Here is a list explaining some of the more relevant characteristics and capabilities of the GPS products in our roundup.
Accuracy
Today, most civilian GPS units are typically accurate to within 10 meters. They make use of various technologies, such as the Wide Area Augmentation System (WAAS) and Differential GPS, both of which help improve accuracy by alleviating position and signal errors.
Performance
All of the units we tested have similar performance characteristics and can attain a "cold" fix, meaning they must determine their positions from a completely new location, seeking out signals from the nearest satellites, which usually takes a few minutes. They are also able to attain a "warm" fix within 15 to 40 seconds, which means that each unit is near enough to its last recorded position to extrapolate where the satellites should be located.
Device Basics
The devices in our roundup weigh from about 5 to 9 ounces with the batteries installed. Each device ships with built-in memory. The least-expensive devices—such as the Garmin eTrex ($120 street)—have less than 1MB of on-board memory. This type of receiver has no built-in maps and can only record your position and a few routes. At the high end, Magellan recently began shipping the Magellan Meridian Color ($499 street), the first standalone handheld GPS receiver with a color screen. The Meridian Color also comes with 16MB of built-in memory, and you can add from 8MB to 64MB of memory via an SD card.
All of the manufacturers in our roundup offer advanced models with more than 16MB of memory via either additional built-in memory (as with the Garmin eTrex Vista or the Magellan SporTrak Pro), or some high-end models (such as the Lowrance iFinder Plus or Magellan Meridian Color) can use optional memory cards. This added memory can be in the form of either MultiMediaCards (MMC) or SecureDigital (SD) cards.
Engineers and designers of handheld GPS devices have to sacrifice some features to achieve these devices' small size. For example, the control buttons on all of the Lowrance and Magellan models are located on the top faceplate, below the display. The Garmin eTrex line, however, positions most of its controls on left- and right-hand sides, allowing for a slightly smaller form factor.
Batteries, Batteries, Batteries
Backlighting, which illuminates a device's screen in low-light conditions, is a big drain on battery life and can cut a unit's runtime in half. Don't plan on keeping backlighting on for long periods of time. If you anticipate needing this capability, especially if you go on a trip for more than a day or two, plan on bringing extra batteries or use your flashlight to view the screen whenever possible.
Tips For Urbanites
Although you get great coverage with the receivers we reviewed when you're out in the open, they can lose their signals when you're in a building's shadow or your view of the sky is otherwise obscured. This loss of signal can be seen easily by going to a device's satellite status screen and observing how many satellites are available. For instance, when walking between tall buildings or under construction scaffolding in New York City, you will immediately lose a signal. But any time you're in the middle of a street you will have a great signal—you just have to remember to dodge traffic.
Built-In Maps
The models reviewed here (except for the Garmin eTrex and the Magellan GPS Companion) come with basic built-in maps that include highways, major roads, parks, waterways, airports, cities, and marine navigational aids (such as fixed and floating buoys, obstructions, wrecks, lighthouses and marinas). Using any of the devices in the field will provide you with your precise location in terms of latitude and longitude. In most cases, however, their built-in maps provide only the sketchiest context for a particular location.
For instance, when using GPS devices during travel, the built-in maps will suffice for a road trip limited to major highways or interstates. But if you want detailed map information about your final destination or stops along the way, you must download specific data from the software packages.
Additional Map Data on CD
Manufacturers offer either their own or third-party map software on CDs. Garmin and Magellan offer their software as options, while the Lowrance model we reviewed comes bundled with MapCreate 6, map software that covers all of the eastern and western United States.
The additional software for each device is basically used the same way. From your PC, you can either run the software from the CD or install it the hard drive. From there you can view the maps. Once you've chosen an area for travel, you then select the level of detail you'd like to transfer to your GPS device. The more detail you add, the more your device's memory capacity is used. You then download the data directly to the GPS via a serial cable or, in the case of the Lowrance device, to an MMC card.
The manufacturers here have done a pretty good job of covering the cities, streets, roads, highways, and destinations in the U.S. Some are more accurate than others, especially when you get down to details, such as restaurant listings that frequently change. And the same is true for marine aids to navigation. Look for reviews of GPS software soon at PCMag.com.
Topographic maps are available from Garmin and Magellan. Garmin's maps are part of its optional four-CD bundle that covers everything from topographic features to roads, waterways, and restaurants. Magellan's is separated into two single-CD optional products. One is called MapSend Topo in the United States. It has much of the same data about cities and roadways as the company's MapSend Streets & Destinations in the United States software, as well as added topographic detail.
No one should expect to get topographic maps with the comprehensiveness of, say, a U.S. Geological Survey (USGS) 1:24,000-scale topographic map (also called the 7.5 minute quadrangle). Hardware and memory requirements would simply be too high for most home PCs and even the most pared-down maps would outstrip the capacity of GPS device when downloaded. But both Garmin and Magellan offer good detail when viewing the maps on your PC's screen. Magellan, though, has done a far better job of transferring topographic data for display on its devices. Garmin's software, on the other hand, transfers far less detail, such as contour lines, to your handheld than do the Magellan products. Lowrance is in the process of developing a topographic product, but the company did not specify a release date.
Basic PC Requirements
While map software requirements vary a bit, here are the most basic requirements.
