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Using GPS

December 17th, 2009

There are many different styles, types and sizes of GPS units available.  Here are a few practical things you can do with a good GPS unit while exploring the woods:

  • Pinpoint your exact location in longitude and latitude even when its dark, foggy, or you don’t otherwise have the slightest idea where you are.
  • Determine the distance and direction from your location to another specified point.
  • Mark where you park your car, so you always know which way to get back.
  • Establish your altitude, and track your elevation history as a profile.
  • Mark locations along your route, or intended route, with “waypoints”
  • Show what direction you need to go to get back on track.
  • Offer traditional navigation assistance with a built-in digital compass, if available.

But here are a few other real-trail things that GPS ads won’t always tell you:

  • You must still carry a map and regular compass. GPS units don’t always work the way you might expect, and you don’t always have the coordinates you need for a destination, so you need a paper map for reference and a compass as backup.
  • GPS units don’t work well, if at all, in buildings or under tree heavy cover. So if you’re in a forest, you may need to find a clearing to set your position, which isn’t always easy.  One thing to look for is a high sensitivity receiver when purchasing a unit.   This can help with some of these problems.
  • GPS units go through batteries if you keep them on for extended times – which you need to do for tracing routes, for instance.  Always carry extra batteries.
  • When a GPS unit indicates you are one mile from a designated spot, that is an “as the crow flies” mile, not a trail mile.
  • Don’t take it out for the first time without learning something about it at home first.
  • The first thing a GPS unit does when you turn it on is to start looking for satellite signals, trying to nail down its position. You may get a signal meter like on a cell phone, or it will tell you how many satellites it is communicating with – most need 3-4 out of the 12 to be accurate.

The basic GPS skills:

  • How to set a waypoint of your current location;
  • How to enter the coordinates of a different location from a map or other reference source;
  • How to determine directions from your current location to another waypoint;
  • How to use the built in compass and altimeter;
  • How to replace the batteries.

One of the great things you can do with a GPS unit is record your “track” as you walk.  This is analogous to a digital bread crumb trail and can be set at any interval you choose.  The immediate benefit to this in the field is that you retrace your steps if you wander off the path and don’t have any waypoints marked in the vicinity.  Most websites dealing with this topic suggest setting the interval to .10 miles – meaning every .10 miles it records your position.  All these points are strung together at the end of the trip and can be saved as a .gpx file.  These .gpx files can then be uploaded to popular trail sites such as backpacker.com or everytrail.com.   You can also link pictures to your GPX tracks if the clock on your digital camera and your GPS unit are matched.  Backpacker.com and everytrail.com talk you through this and it’s really easy.  Another huge advantage is that you can search out trips that people have already uploaded and download them to your GPS unit before you go out.  You can also preview the waypoints (marks along the track) and view the track in Google Earth – allowing you to get a 3d view of the trail and elevation profiles.   Very cool stuff.   See the trails section of this website for examples of this in action.

Additional resources:


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