WHAT IS 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.
HOW DOES IT WORK?
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.
WHAT GPS CAN DO
- 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.
WHAT GPS CAN'T DO
- 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).
JARGON
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.
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QUICKSHEETS
FAQs
Q: How do I post my trips on Backpacker.com?
A: To create trips on Backpacker.com, go to www.backpacker.com 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 www.backpacker.com/postatrip. 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 Backpacker.com to my Garmin unit?
A: Log into Backpacker.com 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:
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Software
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Compatible
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Exports to GPS
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Price/Notes
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Garmin Trip and Waypoint
Manager
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PC
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Waypoints, Routes, Tracks
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Free with new Garmin
units; organizes GPS files
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Garmin Bobcat
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Mac
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Waypoints, Routes, Tracks
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Free. Basic maps;
organizes GPS files
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National Geographic TOPO!
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PC, MAC
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Waypoints, Routes
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$100 per state. High-end topo software for trip planning
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ExpertGPS
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PC
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Waypoints, Routes, Tracks
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$50. Seamless topo maps for the U.S.
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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 www.backpacker.com/postatrip 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 www.gpsbabel.org.
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 www.backpacker.com 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 www.backpacker.com/postatrip.
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 Backpacker.com 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: earth.google.com. 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 www.maptools.com.
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.
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READERS COMMENTS
I'm US military, trained in land navigation. The term UTM seems a lot like the grid coordinates we are trained to use on our topo 1000M maps. We usually train to 8 digit coordinates, but some units such as FA use 10. When I'm in a land nav class we use a clear grid overlay on the map. Even though I'm good with map and compass. I hope to purchase a hand held GPS this year for fun. Never hurts to have a backup?
You explained how to down-load tracks from the GPS to the Internet, but how do you up-load the tracks from the internet, or from another unit, to my GPS unit (so that I can follow their trail)? What about marking a track by hand, and up-loading it for a trip??
I have Garmin60csx and download GPX file from here. I can see trail on map waypoint manager. When I download into device, "Truncated" window pops up and I see part of trail and all waypoint.
Any help?
I have Garmin60csx and download GPX file from here. I can see trail on map waypoint manager. When I download into device, "Truncated" window pops up and I see part of trail and all waypoint.
Any help?
Actually the 1st GPS Space Vehicle was launched in 1978. There are at least 40 operational SVs in orbit today, with GLONASS, the Russian counterpart to our system having 21 SVs in operation today. The European system, Galileo, if it ever works should add 30 more SVs. China has 5 SVs in orbit and plan to launch another 25.
That adds up to 116 operational GPS satellites by 2016.
Most handheld units will operate using most coordinate systems. Most units, if WAAS (Wide Area Augmentation System) capable, should be able to realistically locate one to within 15 feet of the coordinates shown on the display.
Units that are used for surveying work in pairs with a corrected position being continously fed via radio or telephone communications. These units can reliably locate the user to within 6 inches or better, if a clear signal is received. Unfortunately, the carrier transmission is a fairly weak signal. Survey grade measurements usually cannot be achieved under medium foliage or structures.
Incorrect information:
GPS cannot tell you "exactly" where you are.
GPS may err in displayed elevations by more than 30 feet.
Latitudes and longitudes are usually expressed in units of degrees, minutes and seconds.
Jargon:
NAD 27 = North American Datum of 1927.
Based on the Clark Ellipsoid of 1866, it was a coordinate system devised for the U. S.
NAD 83 - North American Datum of 1983.
Based on the WGS 84, it is a system devised to apply to the entire earth.
Interesting fact: One second of longitude (or latitude) approximately equals one nautical mile (6,000 feet).
How do i convert waypoint numbers on go4awalk.co.uk walks to lat/long coordinates so i can enter the walk into my garmin gps60
thanks
How do I download a hike from backpacker.com to my Delorme PN-20 GPS. I am lost on how to do this process, please help?
john_podlewski@yahoo.com
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