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Using GPS


Its full, unglamorous name is Global Positioning System. Launched by the U.S. military in 1990, GPS is a network of 24 global positioning satellites that orbit the planet, beaming radio signals back to Earth to receivers in cars, boats, planes, and hikers' hands.


After receiving radio signals from three or more satellites, a GPS receiver can triangulate your position and display it on-screen as a set of coordinates. Once it picks up four or more satellites, you can get your position in three dimensions, including altitude. It's the world's most precise way to navigate; the typical accuracy of a hiker's unit ranges from 3 to 30 meters.


  • Provide an exact geographic fix that can be plotted precisely on a map.
  • Tell you the straight-line distance and direction to your destination.
  • Record the day's travel as a "track," creating a highly accurate bread crumb trail you can reverse and follow home, or transfer to computer.
  • Tell your altitude within 30 feet.
  • Provide detailed trip information, such as mileage, speed, and elevation gain.
  • Warn of topographical roadblocks like rivers and deep canyons, as long as you've loaded topo maps onto the unit.


  • Provide enough map detail to plan long-distance routes or navigate through tricky terrain (pack topos or use our Adventure Planner mapping software).
  • Warn of detours due to recently rerouted trails, fallen bridges, or natural disasters (call ahead or check recent trip reports on our site).
  • Replace basic navigation skills (get a book or friend to teach you how to use a magnetic compass, read a topo map, and plot a route through terrain).


Datum: Also called map datum. Every map has a "datum," which describes the survey grid used to match the coordinates and features on the ground. Most topos maps are in WGS 84 or NAD 27. Always match your GPS with your map's datum, located on the bottom of the map. Caution: If you're using a NAD 27 map and WGS 84 on your GPS unit, you could be off as much as 1/4 of a mile.

Latitude/Longitude: A traditional standard for representing your position on an east/west, north/south grid. Maps display this grid along their perimeter.

Point of Interest: see "Waypoint"

Route: A file of linked waypoints saved in your GPS unit or computer. Not as detailed as a track.

Track: Also called a tracklog. It's a series of tightly recorded waypoints automatically recorded by the GPS from a bread crumb trail of positions you've passed through since powering up. Displayed on your GPS screen, the track allows you to reverse your course of travel. It can be transferred to our Adventure Planner mapping program or other software on your computer for an exact plot on a map. Our map correspondents set their GPS units to collect a track point every 1/100th of a mile.

UTM: UTM is a reference grid that divides topographic maps into 1-kilometer squares for easy and accurate plotting. It's replacing latitude/longitude as the standard for modern land navigation.

Waypoint: Also called a Point of Interest (POI). It's an electronic pinpoint of a place.

WAAS: Wide Area Augmentation System is a network of ground stations that work with GPS satellites to enhance signal accuracy.



GPS Units

Don't see a quicksheet for your GPS unit?
We'll add it. Contact us.

Post A Trip
Learn how to post trip reports, photos, video clips, and download GPS files on in this step-by-step guide.


Q: How do I post my trips on
A: To create trips on, go to and log into the site or create a new account by clicking the login button on the top right corner. Once you're logged in, go to Upload a .gpx file by selecting Option B. Garmin users can upload their GPS data by selecting Option C. Once your GPS track and waypoints are uploaded onto the site, edit your trip report in the Trip Info page. Add photos and edit your track and waypoints on the Map Editor page.

Q: How do I send a GPS-enabled trip from to my Garmin unit?
A: Log into and go to the trip you want on your Garmin unit. Under Map Tools, select "Send GPS files to Computer." This
downloads a .gpx file (a universal file format for GPS files) to your computer. Now, open the .gpx file in your preferred map software on your computer, connect your Garmin, and send GPS data to unit. Don't have software? Here's a list of common software:



Exports to GPS


Garmin Trip and Waypoint


Waypoints, Routes, Tracks

Free with new Garmin
units; organizes GPS files

Garmin Bobcat


Waypoints, Routes, Tracks

Free. Basic maps;
organizes GPS files

National Geographic TOPO!


Waypoints, Routes

$100 per state. High-end topo software for trip planning



Waypoints, Routes, Tracks

$50. Seamless topo maps for the U.S.

Q: How do I post trips using a Magellan?
A: In order to create a trip on our site, Magellan users need to download their waypoints and tracks onto Magellan's free VantagePoint software. Open VantagePoint and connect the Magellan to your computer. In the map software, go to MY GPS and hit the Synchronize button to download tracks and waypoints from your GPS. You can edit, delete, and add details from your notes to your trail data. Save your track and waypoint data on your computer as a GPX file. Upload this GPX file onto our site by going to and selecting Option B.

Q: How do I convert my old map files (like National Geographic Topo! or Garmin MapSource) for this site?
A: Our site supports GPX files. GPSBabel is the best tool we've found for converting the various data formats found in commercial mapping software. GPSBabel runs on PCs and MACs. To download, go to

Q: What is a GPS-enabled phone?
A: New cell phones are required to have a GPS chip for emergency 911 calls. Some companies like Nextel and Sprint are allowing software makers to enable that chip for other navigational uses. Trimble Outdoors turns phones into full-fledged GPS units on the trail. Most of these phones work outside the cell tower grid to pinpoint your location using GPS satellites, just like a handheld Garmin or Magellan. Right now, more than 50 phones are supported (see list) and the number of carriers and phones is expected to grow monthly.

Q: I see BACKPACKER has a list of map contributors listed in each issue. How do I become one?
A: If you're interested in becoming a regional map contributor, contact our Map Editor.

Q: Is your site compatible with Macs?
A: Yes, Mac users can post trips on our website. Go to and log into the site or create a new account by clicking the login button on the top right corner. Once you're logged in, go to

Q: Can I send maps to my phone?
A: Yes, two ways actually. If you're hiking or biking within the cell grid using a GPS-enabled phone loaded with Trimble Outdoors, you can download a topo, street, or aerial photo at any time. If you plan to explore outside the cell grid, you can pre-send GPS details to your phone from our site. Log into and open the trip you'd like to send to your phone. Under Map Tools, select "Send GPS files to phone."

Q: What is a .gpx file?
A: GPX stands for GPS Exchange Format, which is a data format for the interchange of GPS data (waypoints, routes, and tracks) between applications and Web services on the Internet. BACKPACKER, Trimble Outdoors, Garmin, and others now support GPX files as the universal format to exchange and store GPS data.

Q: What is Google Earth? What is a KML file?
A: Microsoft Word has .doc files. Google Earth uses .kml files to load GPS data onto a 3-D model of the Earth. It's the most impressive way to see a trip, especially in the mountains or on the seaboard. Every GPS trip on our website can be viewed in 3-D on Google Earth. First, download Google Earth onto your computer at: Then, go to any trip and click the "Google Earth" link.

Q: I can't get a satellite fix.
A: Trees, cliffs, and canyons can all block reception, especially when you're using a less powerful receiver. Your best bet is to move higher or out of the trees, hold the receiver above your head, and then point it south.

Q: My map and GPS don't agree.
A: Your map plot may be bad, but it's also possible that your map datums don't match. Look on the lower left corner of your map. If it says 1927 (NAD 27), and your GPS is operating off a 1984 survey (WGS 84), that may explain the variance. Select the correct datum in your GPS's setup menu. If you're not carrying maps, use the default setting on your GPS.

Q: What is UTM? Why does BACKPACKER use it instead of latitude and longitude?
A: UTM stands for Universal Transverse Mercator. It's a reference grid overlaid on topo maps to divide terrain into standardized chunks. Each line of the grid represents a east/west or north/south position, like lat/long. But there's a difference: instead of degrees, hours, and minutes, UTM uses a decimal-based metric system to number coordinates. A UTM grid divides your map into 1 km squares. Positions within each square are expressed in meters. To plot coordinates, you'll need a UTM-gridded map and a UTM tool--a clear plastic card with a tiny grid printed on it. Download a free tool (and find a more detailed tutorial) at

Q: How do I read a UTM coordinate?
A: See example: The map below plots the UTM coordinate: 0559671E 1232685N. The zone (12S) is printed on the corner of the map near the map datum.


  • Although most units last 10 hours on two AAs, always carry spare batteries.
  • To save juice, turn off the electronic compass and use the old-fashioned magnetic kind. Set the backlight time to its shortest setting.
  • If you're not interested in data collecting or route plotting, only power up when marking a waypoint or double-checking your position. You won't get a bread crumb tracklog, but you may not need it.
  • Save your waypoints in sets as distinctly named points for easier filing, storing, and uploading to your computer. It's easier to add notes to those waypoints as well.
  • If you're using tracklog functions (letting your GPS store track points as you walk), make sure your GPS' off timer is disabled, so the unit won't automatically shut down.
  • When using the "Go To" function, allow the directional pointer to re-orient itself after you stop or detour. To avoid waiting, use your handheld compass to follow the correct bearing while the GPS resets.
  • When navigating gets difficult, use all your tools at once: GPS, a handheld compass, and a UTM-gridded map.
  • For serious orienteering, a 7.5-minute top map is indispensable. Downloadable topos for your GPS screen, even the best ones, lack fine topo detail and features like vegetation shading.
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