Land navigation basics
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Navigation is the process of finding one’s present position and then determining the best route to follow to reach a distant goal. We do that today every time we get into our car and pull out of the driveway. Succesful land navigation requires a map and a compass and most importantly, knowledge to use these survival tools.
When we drive our cars, first, we know where we are starting from (home), and second, we know where we want to go, (the grocery store for example), to get to the grocery store we follow a route that has been etched into our mind from repeated trips. We are using a map even though we don’t think about it. A highway map will help us find the best route to a distant city, and if we are pointed in the correct general direction, traveling the interstate is easy when we follow the signs and properly use the map.
What happens when there are no signs and no roads? How do you find your way in the wilderness? To determine the direction, you can use the sun or the stars, or you can use a good compass, to trace distance, identify landmarks, and plan the best route, you’ll need a map.
There are many different kinds of maps. Anything from a hand-drawn sketch to a satellite photo might be of use, but the two most valuable maps to use in a wilderness situation would be a Forest Service map and a topographic map.
Forest Service maps are revised periodically by rangers scouting out the country and are the best guides to the current conditions of roads, trails, and shelters. The local ranger station will stock these maps and have helpful information on weather and hazards to watch for.
Topographic maps are the prime tool of the mountain navigator. A topographic map details the shape of the land and gives a picture of mountains, valleys, and hills through the use of contour lines.
Imagine the earth covered with water so that an entire mountain is barely submerged. Now drain the water 80 feet and draw a ring around the mountain at water’s edge. Continue this process, again and again, lowering the water 80 feet each time and making sure to draw rings at each new water level.
When the water is fully drained away, the mountain will have a series of lines drawn on it called contour lines. When viewed from directly overhead, there would be smaller rings at the top of the mountain and wider rings at its base. Where the rings appear close together, the terrain is steep, where they are wide apart, the elevation change is more gradual.
Topographic maps also show features through the use of symbols and colors. Marketable timber is shown in green. Scrub vegetation is a mottled green and white. Glaciers and permanent snowfields are white with blue contour lines. Blue markings indicate water such as streams, lakes, rivers or springs. Black is almost always used to indicate human features such as roads, buildings, powerlines, trails, etc.
Many topo maps are printed in the 15-minute series with a scale of 1:62,500. That’s about 1 inch to the mile. For even greater detail, the 7 ½ -minute series can be used. With about 2 ½ inches to the mile, this map is popular with those who plan to do cross-country hiking.
Topographic maps can be purchased at most outdoor and mountain shops or online from the U.S. Geological Survey website.
Learning to read a topographic map takes a little practice but soon, the valleys, spurs, ridges, and gulleys shown by the contour lines will jump out and it will be possible to roughly determine your position by finding land-marks around you and locating these on the topo map.
Before you can align the landmarks to the map symbols, the map needs to be facing the right direction. This is called “orienting the map” and will be discussed later in the article. Finding out which way to align your map can be done with natural means or with a good compass.
Finding direction at night can be done by locating the north star (Polaris). By lining up the last two stars of the cup of the big dipper, you can trace an imaginary line to the north star.
On a recent desert trip to hunt jackrabbits, we had lost our sense of direction from constantly turning and chasing these long-eared critters. Everyone in the Jeep swore that north was the opposite direction I was pointing until we all stopped and searched for the big dipper. Sure enough — north was the other way even though our gut instincts said it was in the opposite direction.
During the day, the sun can easily show you direction. Find a straight stick and place it vertically in the ground on a fairly level spot where a distinct shadow will be cast. Mark the shadow tip with a stone. This is your western rock. Now, wait for 10 to 15 minutes until the shadow tip moves a few inches.
Mark the new position of the tip with another stone like the first. Now draw a line straight through the two marks. This line you have drawn is en East-West line. The second stone mark is the east side. By drawing a perpendicular line through your east-west line, you will have a north-south line.
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A compass is by far the easiest way to determine direction. It works on the principle of magnetism and as long as the magnetized needle is not being affected by other metal objects (ice axes, knives, metal buckles, etc.), the needle will align itself with the magnetic field of the earth.
This magnetic flow is toward the north magnetic pole located in Canada, some 1,200 miles southeast of the North Pole.
Avoid using the small, inexpensive pocket-watch type compasses. These will do little more than indicate general direction and are inadequate for use with a topographic map.
A bearing is the direction of a point relative to your position. To take a bearing with your compass, stand looking at a landmark with your body squarely facing it. Hold your compass with the direction of travel arrow pointing directly at the landmark.
The compass should be held level so that the needle swings freely. While holding the compass steady with the travel arrow still on target, rotate the compass dial so that the orienting arrow aligns with the red end of the magnetic needle.
Now read the bearing, in degrees, from the compass by looking at the index line. The bearing is read from the graduated dial at the index line. For example, a bearing could be read as 175 degrees MN (magnetic north).
When you place a topographic map out before you with the reading matter right side up, you can be certain that the top of the map is north and the bottom is south. As you look at the map from this position, the right margin is east and what’s on the left margin is west.
You will also notice on the bottom margin of the map an angle with one leg marked with a star (true north) and the other MN, signifying magnetic north. This is known as the angle of declination.
Because the compass needle aligns itself with the north magnetic pole located in Canada, the difference between true north and magnetic north is given on all topographic maps as an angle with magnetic north either being to the right or to the left of true north depending on your location.
A person residing in Maine would have a declination of 20 degrees west while in parts of Utah, Nevada, and Montana maps will show a magnetic declination of 15 degrees east.
To position a map so that it aligns up exactly with True North is important when trying to identify terrain features. Simply take your compass and set the dial to 360 degrees North. Place the edge of the base plate along the leg of the declination angle marked MN.
Now without touching the compass, rotate the map until the compass needle fits exactly inside the orienting arrow of the housing. Your map is now facing true north.
Once the map is oriented to true north, it is possible to study the terrain in front of you and begin to identify mountain peaks, valleys, and other landmarks. When you can translate the map symbols into real-life terrain, you will be able to locate your general position on the map. To find your exact position, you’ll need the help of your compass.
One of the most confusing aspects of map and compass work has to do with declination and converting magnetic compass bearings to true north bearings. Some of the more expensive compasses have an adjustment screw that permits the angle of declination degrees to be automatically corrected.
Once you have entered your correction — say 5 degrees west on your dial, you can forget about declination when using a map and compass together — all bearings will be read as true north bearings.
Another way to solve the problem is to mark your compass with a piece of tape according to your area’s declination. Instead of lining up the compass needle to the orienting arrow in the compass housing, you simply line up the needle to the tape and then read off the index line the true north bearing.
In order to find your exact location on a topographic map, you need to be able to identify at least two landmarks in your surrounding area. Two mountain peaks will work great if you can positively identify them.
Start by orienting the topo map using the compass and declination angle on the map’s bottom margin. Take a true north bearing of the first landmark. Then without changing the bearing on the compass, align the straight edge of the compass with the peak or landmark on the map. Draw a line along the straight edge through the landmark. Your position is somewhere along this line.
Now take a bearing of your second landmark and draw another line using your compass in the same way (it is still set for the second bearing) and draw a line through the second landmark. Where these two lines cross is your exact position. This process is called resectioning.
To confirm your results, find a third landmark and shoot a bearing again. The third line drawn through the third landmark should cross at the same point as the first two lines. This is called triangulation.
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When faced with very bad visibility, an airplane pilot is forced to fly using only instruments to determine his position. A hiker can be found in the same situation when darkness, fog or snow makes it impossible to see surrounding features.
For this reason, many experienced outdoors-men will take a bearing in the direction of that day’s travel. With this information, it is possible to make it back to camp using the practice known as “dead reckoning?’
In 1985, a party of mountain climbers led by my father was attempting to scale a peak in Zaskar, which is close to the Indian-Tibetan border. A storm hit without warning and with falling snow whipped up by high winds, visibility was reduced to only a few feet.
Because of avalanche danger, they abandoned their attempt to reach the summit and rappelled down the mountain face they had climbed. Once back on the ice plateau where they had left a high camp, the group discovered that their tracks had been erased by the drifting snow.
The alternatives the climbers faced were not good. Without sleeping bags, and with limited warm clothing, bivouacking on the open glacier would be an impossible way to spend the evening. Wandering ahead, in an attempt to somehow stumble into camp, would be equally frightening.
Somewhere to the left, the ice plateau ended abruptly with a 2,000 foot drop off. If they managed to avoid the cliffs, there was the complex crevasse system that lay just to the left of the camp. Going too far to the right could mean walking for miles until finding another ridge tower-ing on its far side. The climbers were cold, and they had no food, water or stove. With the snow flying so furiously, their field of view remained only a few feet.
This could have been a perfect time to panic, but they didn’t. Before leaving camp that morning, they had taken a compass bearing to the ridge they intended to climb. Now, down off the ridge, they took a “back bearing” by adding 180 degrees to the first bearing. With the man at the back of the rope holding the compass and calling “right” or “left,” they set off into the white-out conditions. In an hour, they were safely back to their tents.
Using a map and compass takes a little practice, but with a few practice sessions out in the field, you will develop more confidence in your ability to navigate the wilds by plotting safe routes, always knowing your exact position, and having the ability to find your way when conditions go bad.
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Land navigation basics
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