by Hai Shunxi

Created on: November 21, 2009

Within the past decade, Global Positioning Satellite (GPS) technology became more accurate and less expensive. Because of these trends, many hikers and other back-country enthusiasts began carrying pocket GPS units instead paper maps. Those in the know, however, still tuck a topographic map (affectionately called a topo) into the pack alongside water bottles and first-aid kit. It's not out of nostalgia, either - it's out of common sense.

Sure, GPS units are easy(ish) to use, extremely accurate, and can show you where you've been and where you're going (assuming you work them right). They do, however, have disadvantages compared to paper maps. One is that no paper map ever broke when dropped, nor has one's batteries ever died. Another is that a GPS can display your entire ten-mile route, but only on a screen the size of a playing card. You can spread topo maps out on a picnic table or a flat rock where your whole party can see the route at once. Plus, pleasant "surprises" that might be off-screen for the GPS are there in plain sight on a map.Of course, a topo is just a big piece of paper if you don't know how to use it. In that case, you might as well just pack the GPS unit and plenty of extra batteries. On the other hand, using a topo isn't all that difficult. Here are some hints about planning (and completing) a hike using topographic maps; specifically those available from the United States Geological Survey (the USGS)

The Background

* Every map worth the name has a legend, which displays critical information like a north arrow. Though all USGS topo maps are oriented so that north is to the top, private maps may be rotated or slanted. Look for a north arrow so that you can use a compass to orient yourself.

*Another critical piece of information is the scale. This relates distances on the paper map to distances on the ground. Many USGS topos have a scale of 1:24000. This is an "absolute" scale, and simply tells you to multiply any distance on the paper copy times 24000 to calculate the ground distance. An inch on these maps represents 24,000 inches (2000 feet) on the ground; a centimeter represents 240 meters. Another family of USGS topos has a scale of 1:63560, or one inch equals one mile. If a map does not have a scale, it is not to be trusted.

* USGS topos display coordinates, both latitude-longitude and projected coordinates (usually Universal Transverse Mercator, or UTM). Look for these along the sides, and watch for small black crosses in the body of

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