Wilderness Navigation

Compass

Basic Operation

Maps

Scale

Contour Lines

Map Coordinates
When traveling in unfamiliar terrain or when there are no visible reference points it is useful if not essential to use basic navigation skills to continue. There are two basic tools for navigating, the compass and the map.
Magnetic North
vs True North


Map Bearings
and Staying Found


Resection

Calculating
Travel Times


Compass

A compass is a essentially just a simple protractor. It measures angles. The basic components of a compass are:

Basic Operation

Using a compass is much easier than most people are willing to admit. Remember a compass is a very simple piece of equipment, and navigation is for the most part is an embarrassingly easy skill. If you are traveling towards a peak, or object that you can see in the distance, but will soon loose sight of due to weather or terrain, you can use the compass to continue in the right direction. While you can still see the target use the sighting line to point the compass at the target. Without moving the compass, rotate the housing until the orienting needle aligns with the needle. Now continue on your way, traveling in a straight line to the target. When you loose sight of the target the keep the needle aligned with the orienting needle, and follow the direction of the sighting line. When the needle drifts outside the orienting needle, stop, move the compass (the whole compass and yourself with it) until it is realigned. Continue forward, adjusting when needed and eventually you will reach the target. Congratulations! You are now shooting bearings and following bearings. Most if not all compass work is a variation of this method.

Bearings

When you point the compass at a target and align the needle with the orienting needle, you are taking a bearing.

The front or top bearing/sighting line will align with a number between 0 and 360. This is the angle of degrees the line you will be traveling is from magnetic north. If it doesn’t make sense don’t worry, its not that important. What is important is if the guide book you have been following says to travel at a bearing of 291 degrees, you know to rotate the housing so that 291 lines up with the front or top sighting line, move the compass and yourself until the needle aligns with the orienting needle, and you follow the sighting lines.


Maps

Maps are two dimensional representations of three dimensional features. Its a flat drawing of a changing world. Topographical maps are the standard map for most navigating.

Scale

Scale is a representation of the size of a feature on the map relative to the size of the real thing. For example a lake measuring 1 centimetre on a map with a scale of 1to 50,000, would represent an actual lake 50,000 centimetres or 0.5 kilometres wide. Whether you measure in inches, feet, centimetres, or thumb nails, the relationship is still the same. A stream 2 ˝ thumb nails long on a 1:100,000 scale map represents an actual stream 250,000 thumb nails long. (When working with scales, the metric system is definitely the one to use.)

Common Map Scales and Their Uses:

Contour Lines

A contour line is continuous line of the same elevation around the edge of a feature. Think of it as the edging trim along each layer of a wedding cake. Each line gives an outline of what a feature looks like at regular intervals of elevation. The closer together the lines are, the steeper the slope. For example the close gathering of contour lines on Mt. Wrongagain represents a steep slope. The spread out contour lines indicate a more gentle slope. The contour lines are at 100 foot intervals, that is each line represents an outline of the mountain 100 feet higher than the line below it. Contour intervals will vary with maps, and it is important to check the interval to interpret the map.

To understand the shape of the mountain it is helpful to use the contour lines to build an image of the feature, either in your mind or to draft out a profile on paper. Here is a profile of Mt.Wrongagain.

The mountain has two peaks, with the higher summit on the left. The lower slopes are moderate, becoming very steep towards the summits.

Because the contour lines are at 100 foot intervals we can only estimate what the terrain between each contour looks like. An 80 foot cliff could easily hide between contours and not be recorded on the map. With this in mind it is good to remember that while these maps are generally very good, there is still room for the odd surprise.

One of the most difficult things to interpret on a contour map is a sense of elevation, ridges, and valleys. Here are a few tips. Water always flows down through valleys or gullies, never ridges.

Creeks begin at higher elevations and flow down to lower elevations where they join to form larger but fewer rivers. When contours form a bulge that points from a lower elevation to a higher elevation, it is a gully, valley, or bowl. When contours form a bulge from higher elevations to lower elevations it is a ridge.

Map Coordinates

There are two methods recording a point on a map.

1. Grid system

The grid system is based on the light blue grids printed on most topographical maps. On a 1:50,000 scale map, the grid is 1000 metres square. Along the outside of the map on the top and bottom are a series of numbers called the Easting. The first light blue number will be accumulated distance in metres from 0 on the grid. On the Columbia Icefield map it begins at 467000 metres east. The number increases by 1000 metres with each additional grid east. Mt. Snowdome is located between 478000 and 47900 E. Using a ruler and knowing by the scale that 2 millimetres equals 100 metres; the grid reference is 478400 E. The same method is used to determine the northing, 5781750 N. This coordinate is expressed in several ways:

478400 E, 5781750 N Full description

478400, 5781750 Easting first, Northing second

478400, 781750 The million metre reference is dropped from the northing (often used in guide books)

The grid system is quick simple and very accurate.

2. Longitude and Latitude

This is the traditional system for global positioning. Longitude is a series of imaginary lines radiating from the North and South poles. There are 360 degrees of longitude. Latitude is a series of belts that circle the Earth. The equator is 0 degrees, and the north pole is 90 degreees north latitude. The border between western Canada and the United States is exactly 49 degrees north latitude. For both latitude and longitude, every degree is broken down into 60 minutes. Each minute is further broken down into 60 seconds. Longitude and latitude measurements are located along side the grid measurements, but are printed in black. Longitude is located at the top and bottom of the map. The longitude for Mt. Snowdome is 117 degrees 18 minutes 55 seconds or 117018’55". Latitude is determined with the scale on the side of the map; 52011’22" N. The N represents north, because the same reference is used in the southern hemisphere. The north south designation may be deleted from latitude if it is clearly understood that you are referring to the northern hemisphere. If there is any doubt add the N designation to prevent ending up somewhere in Chile. So Mt. Snowdome is located 117018’55" 52011’22" N.

The grid system is generally much easier to use and is fairly standard for guide books and reference points used by guides, foresters, and land rescues. Most aircraft navigate with longitude and latitude and most gps units give coordinates as longitude and latitude. This makes it important to know both systems. For general travel and route finding the grid is probably a better system. If sending word out for a rescue to park wardens, rangers, or guides the grid system is generally the preferred system. When communicating directly to an aircraft give longitude and latitude. If using a gps be prepared to use both systems.


Magnetic North vs True North

Everything would be fine if whoever built this planet had taken the time to align the magnetic north pole with the true north pole. Unfortunately this planet appears to have been a rush job and it is necessary to adjust for the error.

Earth’s rotation and iron core creates a magnetic field much like giant magnet. However the ends or poles of the magnet do not match the Earth’s geographic poles. To make things worse, the magnetic pole tends to wander or drift, so its location can change over time. Fortunately the drift is minor, and not significant for wilderness navigation.

The difference between the true north pole and the magnetic north pole is easily corrected. Simply add or subtract the difference between the two. For example in the Canadian Rockies the magnetic north pole is about 20 degrees east of the north pole. This is called magnetic declination. If you use your compass to find a bearing of a mountain and it is 270 degrees, you have the magnetic north bearing. Maps are made in relation to the true north pole unless otherwise indicated. So the bearing on the compass is different than the indicated map bearing. To correct take the 270 compass bearing and add 20 and you have 290, the map bearing. Conversely a map bearing of 270 degrees must subtract the magnetic declination to determine the compass bearing. In other words:

Compass Bearing + Magnetic Declination = Map Bearing.

Map Bearing - Magnetic Declination = Compass Bearing.

*These formulae only work west of Ontario

__________________________________________________________________________________________

Map Bearings and Staying Found

On clear days with lots of reference points and a map it is fairly straight forward to wander around and then use the map to orient yourself as needed. If the reference points are few and or the weather suddenly limits the view it is important to know where you are. Lost is lost, and a compass and map will not find you. Know where you are before you loose reference points or targets.

Lets assume you have set up camp on a high alpine meadow, and before going to bed you were able to mark the site on a map. Next morning the cloud ceiling has dropped and you barely see the end of the tent. Somewhere in the mist is a pass that will lead you back down to the valley, but where? Ahh! the map; both the camp and pass are on the map. Lets see, set the back edge of the compass on the camp and the front edge to the center of the pass. Now align the orienting needle with the north/south grid lines on the map. The bearing is 219. Now its time to remember that formula from the great wilderness navigation course you took last year. Map bearing -Magnetic Declination = Compass Bearing. The map says that the magnetic declination is 20. So 219 - 20 = 199. Take down camp, set the compass at 199 degrees and confidently lead the group to the pass. Well done!

Now if you do get lost with a map and compass all is not lost. You can still find your way out with a little luck. First how lost are you? Did you see a reference point in the last few minutes, hours, or days? How far could you have traveled in this time? Estimate the distance that you may have traveled from the last reference point and mark this as a circle from that point on the map. It is reasonable to assume that you are somewhere in this circle. Read the contours within the circle and eliminate the places that you can’t be (glaciers, lakes, cliffs, etc.). Now look at the possible areas that you can be. Are there any large terrain features indicated on the map that you can travel to from all your possible locations ( such as large lakes, roads, well defined trails, railroad tracks, power lines, rivers, etc.). Choose the most reasonable terrain feature, take a general bearing with the compass and begin moving towards it.

Lets say you picked a river, sooner or later you will reach it. Now you know that you are somewhere along this river. Now look around to see if there are any reference points, if there are, you are no longer lost. If there are no other reference points, look at the map and look for stream confluences, large bends, cliff banks, any unique features along the river. Now decide whether it is better to go upstream or downstream to find a reference point. This may be a guess, but try to stack the odds in your favor as best you can. Eventually, you will find a second reference point and know where you are.

When hopelessly lost, stop stay where you are, secure shelter, stay warm, make your site as visible as possible for the searchers, and never admit to taking a navigation course.

Resection

Previously incorrectly called triangulation, this method is used to locate your position with 2 or more known points. Lets say you have just arrived at the Highcountry Hilton, and want to mark the hut on your map. Find two known reference points and take compass bearings off each one. Correct for magnetic deviation (Compass Bearing + Magnetic Declination = Map Bearing) and draw the angle on the map to the reference point. The compass makes and excellent protractor for this exercise. Where the two lines cross is your present location.

If you are in new territory interpreting the contour lines will help you identify features for references. Ideally you want reference points that are as close to 900 apart as possible. This will give you a more accurate reading, but you can further increase accuracy by choosing more than two reference points.

Calculating Travel Times

When traveling it can be useful to estimate your speed to help determine location. If in an area with no reference points or limited visibility you can use the following information to get an idea of your location.

Terrain Rate of Travel
/tr>
Gentle well maintained trails 4-5 kilometres per hour
Rough backcountry trails 3-4 kilometres per hour
Bushwhacking 2 kilometres per hour
Poor weather/whiteout conditions 2 kilometres per hour
For every 300m (1000 ft.) elevation gainedadd 1 hour
This table is best used as a guide and modified as you become more familiar with your own pace.