Backpacker Magazine – May 2010

Navigation: Exploring Off-Trail

When your route takes you off-trail you can still be on course with these navigation tips.

by: Kristin Bjornsen, Dougald Macdonald, & Kristin Hostetter

Tags:
• Gear
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• Navigation
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• GPS
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Decipher the map key
>> Scale Tells you the ratio between a distance on the map and the actual distance. A 1:24,000 scale means that one map-inch equals 24,000 ground-inches, or about one-third of a mile. Most maps also have a graphical bar showing the scale (e.g., 2.5 inches equals one mile).
>> Contour interval The elevation change between each contour line
>> Symbols The markings used to denote trails, streams, mines, etc.
>> Date of publication and revision Reveals how current the map is
>> Magnetic declination The difference in degrees between true north and magnetic north. Since the latter drifts with time, for old maps, get the latest declination at ngdc.noaa.gov/geomagmodels.
>> UTM zone number UTM refers to the Universal Transverse Mercator coordinate system, a grid that’s similar to latitude/longitude but based on the metric system. The zone number indicates which of the UTM’s 60 zones you’re in—vital info for taking waypoints from a map.

Find North with Polaris
Locate the two stars at the rim of the Big Dipper’s cup (called the pointer stars). Draw an imaginary line between them, and follow it (about five times the relative length) to Polaris, the North Star, which is the tail-end star of the Little Dipper. The North Star typically lies within one degree east or west of true north. This only works in the northern hemisphere.


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