gps-receiver

GPS receivers are highly useful outdoor tools. They can provide information on your current location, directions to your destination, and feedback on your progress and performance to your destination.

Note: This article focuses on handheld GPS units and not automotive or fitness models.

Should I Use a GPS or Smartphone?

While some smartphones can be used for navigation, a handheld GPS unit offers some key advantages.

  • Durability: Handheld GPS units are built for backcountry use. Unlike smartphones, most are waterproof so rain or a dunk in the stream is not a problem.
  • Battery life: A handheld typically runs 15 hours or more per charge. Most use readily available AA batteries and have the option of using rechargeable or Lithium batteries for longer life. With smartphones, you are limited to a wall or car charger.
  • Coverage: All a GPS unit needs to accurately locate your position is a view of the sky. Most work well even in dense tree cover. GPS units are not limited by your cell phone provider's coverage area.
  • Features: Handheld GPS units are equipped with a barometer to help track changing weather conditions, an electronic compass for direction finding and an altimeter/barometer to find where you are on a vertical plane. Most units allow you to wirelessly exchange coordinates, trail routes and geocaches. You can even wirelessly connect to computers, heart rate monitors and other ANT-enabled devices.
  • Mapping: GPS units don't require a cell-phone data connection to download mapping, so mapping is always available. Many GPS units support a variety of mapping options, including topographic, road and waterway mapping, plus satellite imagery. More detailed mapping does need to be bought separately, but it is a one-time cost.

How Does a GPS Receiver Work?

GPS receivers use the satellite-based Global Positioning System (GPS). The U.S. Department of Defense operates the GPS, which relies on a worldwide network of satellites that constantly broadcast signals from space to the ground. Your receiver determines its position by combining the transmission data from 4 or more satellites.

Who Can Benefit from a Handheld GPS Receiver?

Hikers, climbers, mountaineers and backpackers: Plan a route on your paper map or digital map and enter the "waypoints" (specific locations) in your GPS receiver. It is very easy to download existing trails or routes from websites. Many of these are at no cost. A GPS will help you get to your destination, whether it's to a scenic vista, sweet crag or your campsite. Be sure to mark your car as a waypoint before you leave!

Backcountry skiers, snowboarders and snowshoers: As snow obscures the trail, a GPS receiver can help you determine the correct path down the mountain. Checking your receiver on the way down can also warn you of any danger zones you noted earlier.

Geocachers: While all GPS handhelds will help you find your next cache, some have dedicated geocaching features. The most common is called "paperless geocaching," which allows you to download and view a cache's coordinates, name, rating and other data on the GPS, so there's no need to bring along paper printouts. You can download this information directly to the GPS from geocaching.com or opencaching.com.

Runners: When training, you like to know how far you've gone and how fast you got there. This data is recorded by all handheld GPS and speed and distance fitness monitors (listed under "GPS sport watches" on REI.com. They can record your travel in a run log, complete with elevation profile. Finally, you can see your run on either a street map or a topographical map. You can also upload it online and share with friends or the competition. For specific training features, you may want to select a dedicated speed and distance fitness monitor.

Cyclists: A bike mount can turn your handheld GPS receiver into a bicycle computer and digital map. Add an optional cadence sensor, and you've got the whole suite.

Motorists: An auto GPS can provide you with audible turn-by-turn directions to many different destinations. Preloaded maps provide information on points of interest such as restaurants, hotels, airports, parks and more. It's the back seat driver you always wanted!

The 4 Basic Functions of a GPS Receiver

All of the GPS receivers available at REI offer these basic functions:

Display position: A GPS receiver can tell you where you are right now by displaying your present coordinates. Your handheld can also show you where you are in relation to other waypoints you've programmed, while mapping-capable units can show you where you are on a digital map.

Tracklog on a GPS Receiver

Record a track-log: A GPS receiver records your travel when this feature is enabled; it's like leaving a trail of digital bread crumbs. This is useful for those wishing to keep a record of their hike, run, or ride. It will also allow you to follow back in their own footsteps.

Point-to-point navigation: A GPS can direct you to a destination or waypoint by giving you the direction and distance to a given coordinate.

Route navigation: You can string together or download a series of waypoints to create a planned path of movement or route.

What GPS Receivers Don't Do

Have realistic expectations for your GPS receiver in order to maximize safety and minimize disappointment.

Your GPS receiver will not replace a map and compass. Why not? A paper map won't break when you drop it, and a liquid-filled compass never runs out of batteries. Betting everything on your GPS receiver is a recipe for disaster.

Your GPS receiver will not get a perfect satellite signal all of the time. Dense vegetation or a deep canyon can obstruct satellite signals. Occasionally, the satellites themselves aren't in an optimal position for accurate calculation of your location.

GPS Accuracy

GPS accuracy is generally around 30 feet (9 meters). A WAAS-enabled (Wide Area Augmentation System) GPS unit can achieve position accuracy of better than 10 feet (3 meters) under ideal conditions, particularly if it has a high-sensitivity chipset.

WAAS consists of a network of ground-based stations in North America that send GPS error corrections to a series of satellites for relay back to your GPS unit. This improves the accuracy of your GPS whenever these satellites are in view and you have enabled WAAS in your settings.

Touch Screen GPS Receiver

Comparing GPS Features

All handheld GPS models provide basic navigation functionality. Many additional features are available that can enhance your GPS unit's usefulness.

Interface: Some models provide familiar touch screens that are intuitive and may be customized by the user. Push-button units can be more easily used with gloves or just by touch (like on a bike), and the functions are clearly labeled.

Color screen: A color display makes reading data and maps very easy, especially when navigating water near land. A few models have black-and-white screens, which helps keep costs down.

Memory: Much like a digital camera, GPS units store data internally and/or on a microSD card. They need this memory to store map data, waypoints, routes and, in some models, even audio, pictures and video. More memory lets receivers hold more data.

Paperless geocaching capability: Data obtained from geocaching.com or opencaching.com includes the cache's description, coordinates, hints, difficulty and terrain. Some GPS receivers can download and display all of that data, saving you the trouble of printing it out. Learn more about paperless geocaching in this video from Garmin.

Altimeter Page On a GPS Receiver

Barometer/altimeter: A barometric altimeter lets you estimate elevation when your receiver does not have decent satellite reception. A barometer is excellent for gauging weather trends. Both tools, however, require a bit of practice and skill. Barometric altimeters rely on ambient, ever-changing air pressure to estimate altitude, so you must calibrate it often. Barometers predict weather best when stationary, as air pressure can change significantly with altitude.

Electronic compass: A GPS receiver only knows what direction it's going in while it's moving. Stand still and it offers no clue—unless you add an electronic compass. This feature can point you in the right direction while standing still. Like the altimeter, it must be calibrated before use. Keep your liquid-filled compass handy as a backup, and remember that features like altimeters, barometers and compasses drain your battery faster when enabled.

Quadrifilar helix antenna: Unlike the flat patch antenna, which gets its best reception when held horizontally, the spiraling "quad helix" antenna gets the same reception regardless of whether held horizontally, upright in your pocket or stuffed into your pack lid.

High-sensitivity chipset: Newer GPS units contain high-sensitivity chipsets that permit the GPS to use a weaker satellite signal when calculating your position. This improves performance under trees or in canyons.

Camera on a GPS Receiver

Digital camera: You can leave your point-and-shoot at home when you pack a GPS receiver with integrated digital photo and video camera. Not only can these models take a photo and display it back to you, they also "geo-tag" the photo so you can see where on the map you snapped the shot.

Wireless data transfer: This allows your GPS receiver to communicate with compatible GPS units or other devices within a 10-foot range without using cumbersome cords or cables. Garmin's ANT+ technology transfers data between ANT-enabled GPS units and ANT-enabled heart rate monitors and bicycle cadence units. You can wirelessly share geocaches, waypoints, routes and tracks between compatible units—a real convenience when hiking or geocaching with friends.

Support of mapping software: Some GPS units can support mapping software and others cannot. The base map provided on many handheld GPS units are very limited. You want to choose a GPS that supports the software requirements you have or need. You can also choose units that have preloaded maps which save you the additional cost of buying maps separately. The coordinate type you use—UTM (Universal Transverse Mercator) or latitude/longitude—may or may not be supported by all GPS units.

Two-way radio: Some devices have integrated Family Radio Service (FRS) radios for up to 2 miles of range and General Mobile Radio Service (GMRS) radios with a range of up to 14 miles (in ideal conditions), plus they get the latest forecast from the NOAA 7-channel weather radio.

Tracker/satellite messaging units: Some GPS units can send your location and text messages to friends, families or search-and-rescue teams via satellite. Other GPS units can warn you when friends, pets or property move outside of a predetermined area. They then work with cell phone networks to send information on their current location to your mobile phone.

Battery life: Compasses and altimeters are very cool bells and whistles on your handheld, but they drain the juice quickly. If you have these features but aren't using them, disable them. Some GPS units support rechargeable nickel metal hydride (NiMH) batteries or Lithium disposable batteries. Rechargeable NiMH batteries are economical; Lithium disposable batteries last longer, especially in cold weather.

Shop REI's selection of handheld GPS receivers.

Topo Map View on a GPS Receiver

Digital Maps on Your GPS

GPS receivers differ in mapping capability. Some models can display your navigational data overlaid on a digital map. Available maps can include marine (nautical charts), topographical, satellite imagery and street maps. Make sure the mapping-capable receiver you want supports the maps you want to use.

Some units have preloaded maps typically featuring cities and major roads; others may be more detailed. Most GPS receivers, however, do not come preloaded with detailed topographic maps.

Check before you purchase that preloaded maps are of a type and scale you will use, as this software takes up a lot of internal memory and often is not erasable. Supplemental maps can usually be added through optional software.

There are several types of software that you can use along with your GPS.

Satellite View on a GPS Receiver

  • Proprietary mapping software from GPS receiver brands such as Garmin and DeLorme may be all that you need.
  • Mapping software helps you load useful trip information into your GPS and then print a quality paper map. You can view a digital topographic map on your computer, study elevation profiles and mark key waypoints. Plug in your GPS and you can download this data to the unit. The trip information will be visible on the GPS "map" screen, even if you have no digital topographic maps uploaded. Next you can design and print a paper map, which can include the waypoints and routes for your trip. This makes comparison of the map to the GPS screen easy.
  • Waypoint management software is optimized to get data and maps onto your GPS. The trip planning functions will be more limited, and this type of software is generally not ideal for creating paper maps.

In general, the type of GPS unit you buy determines the choice of digital maps available to you. Study the software you would like to use to check compatibility before making your purchase.

Types of Digital Maps

Digital maps for a GPS can be downloaded via the web, purchased on a DVD-ROM or an SD card (depending on the type of GPS unit you have selected). Some mapping software applications may also allow map-sets to be loaded onto a specific model of GPS.

Web

Pros: Broad selection of high quality maps, low price.

Cons: Takes time to download. Requires computer interface to load mapping software onto your handheld.

MicroSD Card

Pros: Pops right into your handheld. It doesn't even require a computer, so this is a good option if you're not comfortable with technology.

Cons: Planning your trip in advance is very difficult using this type of mapping software. All of that data on your handheld may slow down some older processors as it renders each page. If you lose your handheld, you lose your software too.

DVD-ROM

Pros: Load the information on your computer to plan your trip and save your waypoints onto your handheld. If you lose your handheld, you haven't lost your software.

Cons: Requires computer interface to load mapping software onto your handheld.

Satellite Imagery

Pros: Lets you integrate high-resolution satellite views with your maps for a true picture of your surroundings.

Cons: Optional feature requires a subscription fee to download imagery and obtain updates.

Map Scale Comparison on a GPS Receiver

Map Scales

1:24,000

Pros: The same scale as 7.5-minute USGS maps, this software shows covered areas in greater topographical detail than 1:100,000 scale maps. Garmin 24K TOPO mapping has detailed topo mapping and accurate street mapping, plus it supports auto-routing on compatible units. With auto-routing, you can pick a destination in the backcountry or in town, and get turn by turn directions on paved roads, dirt roads and backcountry trails.

Cons: Doesn't cover nearly as much area as 1:100,000 scale.

1:100,000

Pros: Covers a much bigger area than 1:24,000 scale maps.

Cons: Provides less topographical detail than 1:24,000 maps.

GPS Receiver FAQs

Q: Do you need to have map images loaded onto your GPS?

A: Provided you are carrying a paper map, loading maps on the GPS is not essential to navigating. Waypoints, tracks and routes can be uploaded and used without being overlaid on a map image. But a graphical map image can make finding your position as simple as comparing the image on the screen to your paper map. When selecting a GPS, consider what map options are available for that particular brand. In general, GPS manufacturers will require you use their maps.

Q: Why does my GPS take so long to find satellites?

A: When a GPS is first turned on, it does not know what satellites are overhead. Once it acquires a lock on one satellite, it downloads the orbital data (the ephemeris) on the rest of the system for the next few days. This process takes time, anywhere from a minute or so in some new high-powered units to 20 minutes or more in older models. The next time you turn it on, however, it will acquire the satellites much faster. If you leave your GPS off for an extended period or travel to a new location, it will need to do this again, so allow time.

Q: How can I improve battery life?

A: Many functions in a GPS unit have a great effect on battery life. The biggest draw will be a backlit screen. Adjust screen settings to keep the screen at the minimum brightness level for your current usage, and set the timeout for the lowest practical time. If you are under heavy tree cover in a deep canyon, your GPS will be struggling to acquire satellite signals. This can drain your battery quickly. You should turn it off in conditions that are unsuitable for use in order to save the battery for when satellites are visible again. Electronic compasses also decrease battery life to a small degree.

Q: If I change my batteries in the field will I lose my data?

A: Data in a GPS is held in flash memory and will be safe while batteries are changed.

Q: What coordinate system should I use?

A: There are many coordinate systems in use, but the most popular are UTM (Universal Transverse Mercator) and latitude/longitude. You can select the system you wish to use in your GPS settings menu. Most GPS units come with latitude/longitude set as the default in the format Degrees Decimal Minutes. This format is the default for geocaching, common in software and web programs, and is often printed around the borders of topographic maps. UTM is generally the preferred system if you will be transferring coordinates between the GPS and a map. Pocket-size grid readers can aid in determining the coordinate of a given point on a map. The system is metric and distances between coordinates can be easily estimated.

Q: What is the difference between a route and a track?

A: A route is a set of directions between a predetermined series of waypoints. When a route is activated, the GPS will point you to the next waypoint in the series, rather than to the final destination. This can provide more useful direction and distance information on your hike. A track is a visual tool that you can view on screen, much like a trail on a map. It can be drawn on a map program for download to the GPS. A track can also be recorded as you travel to give you a visual record of your hike. It can be converted to a route if you need directional information. The track contains data about your hike, such as elevation and time, that can be analyzed and displayed when uploaded to compatible map software.

Shop REI's selection of handheld GPS receivers.

GPS Accessories

If you plan to use your GPS in your car as well as on the trail, pick up a mounting bracket and a power cord that plugs into a car's lighter socket. Bike mounts are also available. A padded carrying case can help protect your GPS from drops.

Shop REI's selection of GPS accessories.

Additional contributors: Derek Klobucher, freelance writer; Bill Loud and Orville Burlison, Garmin sales managers; Mike McCarty, REI product manager.

All images courtesy of Garmin.