Basic Navigation

At some stage any active climber, mountaineer or hiker will find him/her self crossing new ground, be it on approach or retreat. Confidence and competence in the use of a map and compass is vital and can only really come with practice. Trusting the compass and your own ability in a whiteout (diminish vision due to mist or snow) or at night in a storm is not easy, and many a party have found themselves in trouble due to their inability to use the basic tools of navigation.

Maps
Modern relief/contour maps give a good idea of the profile of the country. However, ordinary contour (topographic) maps give the same information to a skilled navigator. A useful scale is 1:50,000 (1 unit on the map = 50,000 of these units on the ground, e.g. 1cm = 50,000cm, or 500m; 1in=50,000in, or about 4165ft).

Apart from features such as roads, buildings, rivers and vegetation, the key element to any topographical map is the contour line. Each line represents a particular constant elevation. The contour interval is the vertical height rise represented by each successive line - this is usually about 10m or 20m (40 or 80ft on US maps). Major contour lines are printed darker and labeled with the height somewhere along their length. The closer together the contour lines, the steeper the slope.

A useful tip is to keep the maps in plastic bags or special map cases, or to laminate them. A soggy mass of wet paper will not be of great help in escaping from a tricky situations.

Navigating by Map Alone Most navigation is actually done without constant reference to the compass. The map is orientated using the compass, then the features on the ground are matched to the map. In general this is sufficient to allow you to navigate to the destination, perhaps with occasional checks of the compass against the map to confirm orientation.

Navigating by Map and Compass In extreme conditions, or in bad visibility, the map features alone may not suffice. You must then navigate using advanced skills, with the compass playing a large role. The compass is essentially a simple device, but one fraught with problems for the untrained.

Compasses have a seldom-recognized 'dip' factor called magnetic inclination (as opposed to the familiar variation) which affects the horizontal alignment of the needle. A compass needle 'weighted' for the far northern hemisphere may 'stick' to the base of the compass near the equator or the southern hemisphere, resulting in incorrect navigation. Check that you have an appropriate compass.

The most useful compass for navigation has a rotating bezel on a transparent base plate, with a direction-of-travel arrow marked on it. These compasses usually have graduated scales called roamer scales, which enable you to measure distance on the map. Many have a number of different roamers to take into account a range of map scales.

When traveling from one point to another you may sometimes follow a simple heading such as 'due north' or 'directly west'. However, navigation is very seldom this straightforward and considerable accuracy is required, for example, if you are heading for a small neck or pass through thick mist at night. In circumstances like this, you have to use bearings.

The compass circle is divided into the familiar 360°, with north being at 0°, east 90°, south 180°, and west 270°. These numbers are referred to as bearings. Experienced navigators can be accurate to within a few meters over large distances.

The compass is used for two functions. One is to take bearings, either (e.g. a distant hill) or by measuring a bearing from one point to another on a map. The other function is to plot or follow bearings. This is when the compass is set to a particular bearing, either by taking sightings along the compass or via measurement on the map. That bearing is followed on the ground or on the map to arrive at a point.

Bearings on the Map
The compass is used here as a simple protractor and the magnetic needle need not be involved at all (the map does not necessarily have to be orientated to north). Bearings for escape routes from obvious points on the climb/hike can be plotted at home beforehand using the map and compass-protractor.

Plot Bearing from Point X to Point Y 1) Place the compass on the map so that one long edge runs between X and Y. 2) Check that the direction-of-travel arrows points to point Y. 3) Turn the rotating bezel so that the NS line is parallels the 'true' NS lines on the map (a conventional map is set to 'true' NS) 4) Read the number on the index line (direction-of-travel line). This is the bearing from X to Y.

Converting this to a Usable Bearing on the Ground You are now at point X, in the dark, and wish to get to Y. If you set 340° onto the direction-of-travel line on your compass, and then followed this, you would not end up at Y! The reason for this is magnetic variation (also called magnetic declination). The magnetic North Pole is unfortunately not the same as the true North Pole, around which the earth rotates on it's axis.

Left of the 0° (Greenwich meridian) line, the figure is, for example, -10°. This figure is subtracted from the bearing of 340° obtained above. You would then walk on a magnetic bearing of 330° to get from X to Y. If you were right of the 0° line, and the variation was +10°, you would add it to 340°, giving a compass or magnetic bearing of 350°. Check the information on the map: it will normally read as 'magnetic variation: 15°E, for example. This means: 'go 15° further east of your true bearing' i.e. add 15°. If it said '15°W', then you would subtract 15°, i.e. go further west.

To Follow a Bearing on the Ground 1) Set the bearing from the map as above, taking into account magnetic variation. For example: 340° +(or -) 15° variation = 355° (or 325°). The rotating dial must thus have 355° (or 325°) on the direction-of-travel arrow. 2) Hold the compass level in front of you and turn it (and your body) until the north needle of the compass lines up with the north arrow on the rotating dial.

More Advanced Skills in Following Map and Compass
In bad conditions, it is easy to lose track of where you are even using a map and compass. Maintaining direction can be done by sighting along the line of travel and identifying a feature, e.g. a prominent rock, on that line. Head for this feature, then resight to the next visible feature. If the terain is featureless, 'leapfrog' by sending a climber/hiker ahead, getting getting them in line, placing another beyond them, then leapfrogging to the front and repeating this. Usually this process is rather time-consuming, so it is often better simply to keep on checking the compass, and maintain direction as best you can. You must trust the compass.

Keeping track of the distance traveled can be useful. By measuring the distance from X to Y on the map, you can then use the scale to work out the actual distance on the ground. For example: If X to Y = 2.5cm on the map, which has a scale of 1:20,000, then the distance on the ground is: 2.5 x 20,000 = 50,000cm ÷ 100 (100cm=1m) = 500m. If you know your pace length (it is advisable to work this out in advance while practicing navigation) then you can count paces (often 2 paces = 1m in difficult terrain). You can also work on time: the average party under difficult conditions walks at approximately 3Kmp = 3000m/60 minutes = 50m per minute. Thus, 500m should take about 10 minutes. This gives you some idea as to when you expect to reach Y. If after 10 minutes you are not at Y, then you must assume that you have made a navigational error and should consider retracting your bearings to X or another obvious 'know' point before the problem becomes too great.

Read more in Garth Hattingh's The Climber's Handbook. This book is a must have for the beginner and expert climber, offering expert information, with pictures and illustrations, on climbing and mountaineering. [Order online]

Source and extracts from: The Climber's Handbook, by Garth Hattingh.

About the Author: Garth Hattingh has over 30 years of experience and has written several climbing and mountaineering books including; Rock and Wall Climbing, Top Climbs of the World, Extreme Rock and Ice, and The Outdoor Survival Manual. These books are available from our online store.

Courtesy and Copyright by: Garth Hattingh. New Holland (Publishers) LTD, London, Cape Town, Sydney, Singapore. Struik (Publishers) LTD, Cape Town.

Distributed by: Struik (Publishers) LTD, Cape Town. ISBN 1 85368 7170.

Updated Wed, 10 October, 2001 http://www.rocksport.co.za