Navigation 101: Using a Compass and a Map
Today’s digital reliance on GPS navigation has all but relegated compass and map use to hardcore outdoor enthusiasts, orienteering clubs, and geography buffs. Using your cell phone’s GPS is fast and effective if you’re within cell range or you cache (download) maps for offline use. Better yet, bringing a GPS receiver that’s compatible with the Russian GLONASS system offers even faster location pinpointing and better overall accuracy, thanks to its additional 24 satellites.
That being said, both cell phones and GPS receivers rely on technology that’s subject to failure, whether you forget to charge a battery or inevitably drop your precious gadget in a river or on a rock. Knowing the basics of compass and map use not only provide backup navigation if you’re deep in the wilderness, but they also offer a fun and refreshingly simple way to navigate. Polish your map reading skills and practice the following navigational tips next time you’re hiking or orienteering through your favorite natural area.
What to look for in a map
Basic orientation simply requires a few simple tools: a navigational compass with a rotating bezel, a detailed topographic map, and perhaps a writing utensil and ruler. Before you can successfully navigate through your favorite slice of national forest or designated wilderness, you’re going to need the appropriate topographic map for the area that you’ll be trekking. What falls under the definition of appropriate? Well, you’ll need the map to be of a large enough scale to show natural and manmade features in sufficient detail. Scale refers to the relationship between the distance on a map and the corresponding distance on the ground, and it’s represented by a ratio usually found on the bottom of a map.
Often chosen by outdoor enthusiasts for its high accuracy, the United States Geological Survey (USGS for you geography buffs) produces topographic quadrangles for every portion of the United States with an orientation-friendly scale of 1:24,000 (except for parts of Alaska where 1:63,360 maps are used). At this scale, you’ll be able to visualize nuances in terrain, pick up where streams and waterways lie, and make out the location of important natural and manmade features that can help you successfully navigate through mountains, dense forests, and everywhere in between.
Taking a bearing
Taking a bearing is a simple way to determine the direction of your destination in mind. To do this, you’re going to need to find your current location on the topographic map. Let’s call this Point A. If you have a writing utensil, you can make a pinpoint on the map for easy viewing. Now locate your destination on the map and make another pinpoint. Let’s call your destination Point B. Calculating a bearing is simply determining the direction of your destination from Point A to Point B. You’ll use this direction as guidance as you walk to your destination.
The first step in finding your bearing is to align the outside edge of your compass, as to connect the dots, from Point A to Point B. If the two points are too far apart, it sometimes helps to have a ruler handy, so you can draw a line to match to the compass’ edge.
Once you’ve aligned your compass’ edge from Point A to Point B, turn the compass bezel/housing until the North dial marker (referred to as zero degrees) matches due North on the map. The direction you need to walk is where the large front arrow and solid marker on the underlying compass align. There will sometimes be text saying “Read Bearing Here,” just in case you’re confused as to where the bearing lies. This is the direction of your destination.
Now that you’ve found your bearing, don’t spin or rotate the compass’ bezel. Your bearing is locked into place, and you simply need to align the compass’ North needle with the arrow outline. To do this, hold the compass straight in front of you, parallel with the ground’s surface, at a 90-degree angle. Now rotate your body until the compass’ needle falls into the north arrow’s outline (usually a hollow red arrow on the compass’ center). Voila! You’re bearing direction is straight in front of you, guiding you to your destination.
Following a bearing is a great way to reach a destination if you’re walking through a relatively flat area that’s devoid of natural obstacles that are blocking your path. In reality, it’s very difficult to follow a straight line through rolling hills, thick vegetation, and steep, elevated terrain. To solve this problem, aiming off is an appropriate solution that involves following an alternate bearing to either side of your intended destination. Look for something like a road, trail, or waterway that will be easy to follow once you reach your alternate destination. That way, even if you’re a couple hundred yards to one side of your destination, all you have to do is simply follow the natural or manmade feature in the opposite direction until you’ve found your intended destination.
Complicating things a bit, magnetic north and true (geodetic) north are located several hundred miles from each other. To account for this difference, you can consult the declination diagram at the bottom of your topographic map, or you can simply use this handy link provided by the National Oceanic and Atmospheric Administration: http://www.ngdc.noaa.gov/geomag-web/.
Once you figure out the difference in degrees for your region between magnetic north and true north, you have to add or subtract the amount of degrees from your compass bearing, depending on where you’re located in North America. The difference in degrees can be quite substantial in eastern and western regions or virtually non-existent in central states, such as Minnesota or Iowa.
Note that serious navigational compasses have adjustable declination settings that offset the declination for you, allowing you to take a bearing without worrying about adding or subtracting degrees. All you have to do is set up the compass prior to a backpacking trip or excursion with the appropriate declination difference, and you’re good to go.