Map and Compass Navigation: Trail Guide
Having a Backup Map and Compass Will Keep You Moving in The Right Direction
Learning how to use a traditional compass and map to find your way is as paramount as knowing how to change a tire or liberate a stuck Jeep. When important systems fail, you must have a backup. And the most reliable backup for a navigation system is a quality paper map of the area and a traditional compass.
Learning how to use a traditional compass and map to find your way is as paramount as knowing how to change a tire or liberate a stuck Jeep.
Described by one off-road enthusiast as being “in dreadful condition,” the Morrison Jeep Trail rises sharply up the precipices overlooking Clark’s Fork of the Yellowstone River north of Cody, Wyoming. Though not as treacherous as the Fordyce Creek Trail in Truckee, California, nor as technical as the famed Rubicon nearby, the Morrison Trail features 27 very tight switchbacks on the main ascent to the top of Beartooth Plateau. There are breathtaking views of Sugarloaf Mountain to the west, Bald Peak across the river to the east and White Mountain to the south.
What’s special about the Morrison Jeep Trail is that it has the distinction of not being on your rig’s navigation. In-car navigation systems are great as long as there are roads and cardinal directions to keep you pointed in the right way (and you have it updated regularly), but as soon as your wheels roll off the map, your navigation system is just a pretty green picture providing no help except to point north. But what if that stops working? What happens if your vehicle’s battery drains to zero or your phone goes dead? Or you don’t have cell service? You’ve got nothing left but good old map and compass navigation.
What Kind of Map and Compass Navigation?
There are road maps, resource maps, physical maps, and political maps, but the kind you always what to carry with you are topographical maps. John Wesley Powell, the director of the United States Geological Survey (USGS) from 1881 to 1894 once remarked: “A government cannot do any scientific work of more value to the people at large than by causing the construction of proper topographical maps of the country.”
There are a few websites that will sell map and compass navigators a topo map of any area in the country and even Google offers its cartography services that you could print out. However, the best, most accurate and most widely used are the topographical maps provided by the USGS, a program started in 1884 and updated regularly by the government.
Called a quadrangle, these topographical maps are drawn to 1:24,000-scale and contain 7.5 minutes of latitude and longitude (1/32nd of one degree), where one inch equals 24,000 inches of real-world land. It wasn’t until 1991 that the USGS completed mapping the entire lower 48 states in this scale. The coverage includes an impressive 55,000 7.5-minute quadrangle maps. The map’s real qualities lie in its colors, lines, and details.
The USGS included on its topographical maps almost 200 different features separated into five color groups. Cultural features, smaller roads, buildings, and man-made things such as trails are printed in black; main roads and political boundaries are in magenta/red; woodland areas and other vegetation are green; rivers, lakes, glaciers, and water features are blue; and contours lines, depressions, and mountain features are printed brown. If you see purple, that means it is an update from a previous version (though it’s a color no longer used by the USGS).
The various colors make map and compass navigation, but there’s a skill required to see a topographical map as it was intended: real-world terrain. Once mastered, by merely looking at a topo map, you’ll visualize the terrain as if you were standing before it. It is a skill that takes some experience.
Contour lines represent segments of the ground that share an equal elevation as well as defining the shape of the terrain’s features. They parallel each other and approximately the shape of the one above it and the one below it. However, not all contour lines are created equal. Heavier contour lines are known as indexed contour lines and normally show elevation in feet.
Typically, every fifth contour line is an index contour line. Lighter contour lines that fall between indexed lines are known as intermediate contour lines. These lines do not have their elevation listed and are found in sets of four between indexed contour lines. At the bottom of the map, under the scale, the contour interval will be listed. Normally it is 40 feet, meaning that there is 40 real-world feet between contour lines and 200 feet between indexed contour lines.
The closer the spacing of the contour lines, the more rapid the elevation change of the feature. This is important when traversing an unknown region, as a steep hill or deep gorge would have contour lines close together, while widely spaced contours indicate a gentle slope.
Using a Compass
The compass always points north. The problem is that the compass doesn’t point directly to the North Pole. Instead, it always points to the magnetic north pole, which is currently somewhere in northeastern Canada. The map, however, points directly toward true north, and you need to know the difference in the real-world situation you’ve found yourself in.
Magnetic declination is the number of degrees and direction between true north and magnetic north. Because declination varies over time, it is advisable to get a reasonably current figure by using a current map. If magnetic north is east of true north, the local declination is positive. If magnetic north is west of true north, the local declination is negative.
Map and Compass Orientation
It is common practice that all maps are oriented with true north at the top. At the bottom of the map, a symbol of arrows pointing to the geographic North Pole (shown by a star), magnetic north (MN) and grid north (GN). By coordinating a compass with a map, you’ll be able to match the features of the map with features in the real world, allowing you the ability to navigate toward any destination on the map.
Magnetic declination is the number of degrees and direction between true north and magnetic north. Because declination varies over time, it is advisable to get a reasonably current figure by using a current map. If magnetic north is east of true north, the local declination is positive (like shown here). If magnetic north is west of true north, the local declination is negative.
Basics of Map and Compass Navigation
To orient your map, place the compass on the map so it is parallel to the north-to-south border of the map, known as the “neat line.”
Rotate the compass dial until north on the compass ring lines up with north on the map. Find the magnetic declination on your map. In this case, it is 15 degrees positive (east). If the local declination is positive, subtract the declination amount from the bearing you just derived. If the local declination is negative, add the declination amount to the bearing you just derived.
Holding the map and compass steadily together (the compass should still be on the north-to-south map “neat line”), rotate the map and compass at the same time until the red magnetic needle orienting arrow on the compass face line up. Your map and your compass are now oriented to true north. Look around and compare the physical features around you with your map; they should be an exact match.
Optional Orientation: Terrain Association
The most reliable backup for a navigation system is a quality paper map of the area and a traditional compass.
What if your compass breaks? You take a spill down a hill, and you lose it, or worse, it breaks on a rock. What then? How will you know where you are going or which way you need to go? You’ll have to orient your map based on what you can see, and this is easier if the area you are in has definite features like a tall mountain or a deep ravine. If you are in an area with little to no reference points, like on the plains, in sand dunes or in the rainforest, it will be considerably more difficult—but not impossible.
Hold the map in front of you and look around. Are there mountains? A cliff? A river? Can you find it on the map? If so, which direction is it in? Turn the map so it faces in that direction and then look for something else to cross-reference or a defining feature on the first object to further your orientation. Map and compass navigation is never an exact science, but at least it will help you head in the right direction.
The Features on a Topographical Map
The examples here are from the Waterman Mountain and Fontana quadrangles in Southern California, about 10 miles north of Pasadena in the Angeles National Forest and about 40 miles east of Los Angeles in the San Bernardino Mountains, respectively. The mountains north of Los Angeles offer a wide range of topography that well illustrates the various elements of a typical topographical map. This stuff is critical knowledge for all map and compass navigators.
01/ Contour Lines
02/ Peaks and Highways
03/ Campgrounds and Rivers
04/ Planes, Canyons, and Roads
05/ Jeep Trails and More
The Map Legend
Various symbols depict features such as building, campgrounds, springs, water tanks, mines, survey markers, and wells. Names of places and features generally appear in the color corresponding to the type of feature. Different colors and particular symbols more or less represent their parallels in nature. The difference between a sand beach and a gravel beach, for example, is the size of the dots representing the grains of sand.
Though there are around 200 symbols used on the 55,000 topographical maps currently in use by the USGS, these are a representation of the more popular symbols you’ll need for map and compass navigation.
Editor’s note: A version of this story previously appeared in YOTA Winter 2022.