It is a popular misconception that the handheld GPS (and other “location aware” devices like the iPhone) completely replace a map and compass for land navigation. In some cases, like an afternoon hike on a well-traveled hiking trail going sans map and compass is probably fine, but for serious outdoor adventures, a compass (and a map) is an essential companion to your handheld GPS. Here’s why.
1. Determining Directions with GPS Only Works while Moving
GPS units display accurate directions to you only while you are moving. When standing still or moving very slowly you’ll get directional readings that vary wildly, which is not very handy if you are standing on top of a mountain trying to figure out which direction you are facing.
Some handheld GPS units and newer iPhone models have built-in electronic compasses that work independently of GPS satellite communications through a technique called magnetic induction. These electronic compasses detect the Earth’s magnetic field, producing the same result you would get with an “analog” compass. Accuracy of sophisticated electronic compasses for marine navigation can be very high (to match the 4-digit price tags), but don’t expect more than 2 to 5 degrees of accuracy with your handheld GPS or mobile device compass.
2. Distant Terrain Features are Easier to Work With when Using Map and Compass
Trying to figure out your location on a small GPS or iPhone screen can be challenging in a backcountry environment (especially if you lose satellite coverage!). Plotting courses on a paper map not only works without satellites, but allows you to view topography information over a broad area without zooming in and out. Another reason to bring along a compass is that it is difficult to accurately plot bearings on a map with a gps or phone.
3. No Batteries Needed
Finally, the possibility of a malfunction is much smaller with a handheld compass. Rugged gps units rarely just stop working, but it does happen—especially when they get dropped on hard surfaces. They also go through batteries very quickly if you are referring to them constantly. A better solution is to use your GPS power sparingly and refer to your battery-free compass often.