Maps and map-reading
You will probably need to get some maps if you intend to do some serious walking, but don’t go to the expense of buying full sets of maps right from the start. Try to keep your ambitions modest at first and find out if you are going to enjoy the activity. Go with friends, experienced friends if possible, and try joining your local rambling club or footpaths group. Ask questions and find out what maps the members use and get them to show you the routes. You may not even need a map at all for easy walks on well-marked footpaths in good weather. Handbooks and walking guides can be useful for beginners.
Do not be put off by the intricacies of map-reading lessons. If you do not learn immediately how to orient a map, or do a resection, or interpret contours, don’t worry. It will come with time because there is nothing simpler than reading a map. It is no more difficult than interpreting the plan of a room, showing doors, windows, cupboards and a fireplace; instead the map shows roads, rivers, villages, woods and hills. It is just an accurate picture of the local area as seen from a helicopter. Just as you can cross the room from a door to a window or from a window to the hearth, you will be able to follow the river bank or find your way from the corner of a wood to a bend in the road, provided the visibility is good.
A lot of maps are free; they are usually obtained from tourist offices, public libraries, hotel foyers, or bus and train stations. You can leam a lot about local walks from free maps. They do not usually show hills and valleys very well, although ‘shaded’ sides of hills may have deeper colour tints, with picturesque effects, which are useful and easier to understand than contours. Woodlands and forestry plantations are often coloured green. As well as a plan (or bird’s eye view), some of these hand-outs have landscape drawings of hillsides with recommended routes indicated by dotted lines; but if you are thinking of hill walking you must be cautious.
Most houses and cars have a proliferation of road maps, bought from garages and supermarkets or from motoring organizations. As a passenger in a car or bus, it is good training for walking to pretend you are the navigator of a rally car, and plan what you would be able to tell the driver in advance. Make sure the map is pointing the correct way to correspond with your travel direction and anticipate what side-roads, villages and landmarks will come next. You will soon realize the limitations of the map and that you need a lot less map detail for driving than for walking footpaths. Most road maps have no indication of uphill or downhill, except that major hills are marked with a litde black triangle with the height, usually shown in feet.
There is a lot of really interesting walking around nature trails, castles, bird sanctuaries, archaeological digs, wildlife parks and zoos, great houses and gardens. You may have to pay to get in, but it is all good exercise, and often there are places for refreshment. Included in the entrance fee you may get a brochure of the site with an adequate map. If you practise hard and get competent enough to reach the reptile house rather than the polar bears, it will be much easier when you go out into the countryside with a good map. If you already have a Landranger map of your area, you will be able to find parking places, camp sites, ancient monuments, view points and so on marked in blue. National Trust properties are outlined with thin, red lines, while National Parks and Forest Parks are highlighted with a thick yellow border. Youth Hostels, which provide good, reasonably priced accommodation where you meet interesting people, possibly also on walking tours, are marked with small red triangles.
So, let’s find a map, go out and try it. If the country is flattish there will be very few contour lines anyway, so you need not bother about them at this stage. Notice the blue wiggly lines on the map — these are probably streams. Follow a stream marking until it gets thicker or joins another river or flows into the sea and you will get the direction of flow. Already you are beginning to get the idea of which is higher and lower ground. The red or orange lines indicate roads (although motorways are shown in blue); study the legend in the margin of the map and you will find out what all the conventional signs mean. The important ones for ramblers are those depicting public rights of way (not applicable to Scodand). The footpaths are thin red broken lines; while bridleways, for passage on foot, horseback or pedal cycle, are shown by thicker red broken lines with longer dashes. Find the start of a footpath near you (probably marked by a signpost anyway) and go for it; the more you use a map in the field the easier it gets, and near towns and villages you can afford to learn from mistakes.
To set the map in relation to the ground; just turn the map round until the road on the map points along the real road and the footpath on the map points along the actual footpath. Walk along the footpath until you come to a bend in it, check that the bend is shown on the map, then check your map is still oriented – that is, pointing the correct way in relation to the change in direction of the path. Use the map always pointing the correct way, until you are fully acquainted with the method, even though it may mean reading the place names upside down.
Consider the scale of the map. If it took you 15 minutes to walk to the first pronounced bend in the path, the distance you walked would be about 1 km (½ mile). If that distance on the ground is represented by 2cm (0.787in) on the map, the map you are using would be drawn to a scale of 1:50 000. This ratio is said as ‘one to fifty thousand’, meaning that 1cm on the map represents 50 000cm (500m) on the ground, and so 2cm measured on the map represents twice 500 equalling 1000m (1km). Measuring 2cm on the map is easy because this scale of map is printed with a grid of squares covering the whole face of the sheet, and each square has sides of 2cm. The squares are called kilometre squares and the grid is called the National Grid.
A good way to practise measuring scales is again when you are being driven somewhere in a car. Find out the length of the stretch of road on the map by marking the edge of a sheet of paper with a pencil. The straight bits are easy, but when you get to the bends and twists you will need to guess by juggling the edge of the paper round the bend. Each section, straight or curly, follows on from the last. Check the total length of the marks against the scale at the top of the map marginal drawings, or, better, the number of grid squares the marks cover. Get the driver to set the trip odometer at zero, then check the road distance at the end of the journey. Unfortunately, most British cars show distances travelled in miles, but to convert to kilometres just multiply by 8 and divide by 5.
Another way to measure off the map is to use a device with a knurled nut rotating around a screw thread. This is known as a map measurer, but I find the gadgets unnecessary.
I know that the breadth of my right middle finger is exacdy one grid square on the 1:50000 maps. You can also use a bit of string or a malleable copper wire. We used to use pipe cleaners, but nobody smokes pipes these days. I have just had a tip that a piece of waxed dental floss works well.
The straight line across a grid square represents 1km, but the diagonal distance is approximately 1.4km (about ½ mile), which will help you to make a quick rough estimate. The quarter circle with a radius of one grid square represents approximately 1.6km (1 mile) on the ground.
The 1:50 000 Landranger map is best if you intend to walk further afield than limited tourist areas, because for the same size, weight and cost, the map covers four times the area of the Pathfinder 1:25 000 map, but in less detail. For example, field boundaries are not usually marked on the Landranger maps, but they are good enough for all except the most jagged, complicated mountains, and that is hardly ‘walking country’ anyway. Outdoor Leisure maps cover popular mountain, moorland and tourist areas and are drawn to the same scale as the Pathfinder maps.
Let’s get the business of small and large scale sorted out from the beginning. A small scale map shows features small, so that a lot of detail has to be missed out altogether. This type of ‘school atlas’ map is good for showing the shapes of counties and countries. Large scale maps represent much less area for the same size of paper sheet, but details can be printed so large that your own back garden can be made out.
Contours, the reddish-brown lines forming intricate patterns on topographic (relief or contour) maps, are lines to indicate the shapes of hills, valleys and slopes. They represent level planes at set intervals. Submarine contours were the earliest to be used on charts to show the shape of the sea bed, but on walkers’ maps the lowest contour is usually mean sea level, so the ‘zero’ contours show the outlines of islands in the sea.
Contour lines are numbered with the bottom of the printed number on the lower part of the slope, so that is easy to know which way is uphill and which is downhill. The numbers represent the height of that particular contour line above mean, or average, sea level. Every fifth line or index contour is drawn thicker, so that on mountain slopes, which have lots of lines, they can be counted in fives rather than singly. To get the idea; imagine that you have taken a roughly cone-shaped lump of plasticine and placed it in a transparent mixing bowl.
Suppose it is the model of an island, a bit like St Michael’s Mount protruding from Mount’s Bay in Cornwall, and that the base of the cone is at mean sea level. Looking down into the bowl, the shape the lump makes with the bottom of the bowl is the same shape as the zero contour. Draw the shape on a relief map. With a rule, graduated in centimetres say, alongside the bowl, pour in liquid to the height of 1cm. The new shape at the liquid level can be drawn inside the zero contour and numbered 1. Pour in more liquid to a new height of 2cm. Keep pouring and drawing alternately until the lump is covered and you will have an accurate relief map of the plasticine. The scale of the map will be full size of course, or 1:1, and the contour interval, also known as the vertical interval will be 1cm. On Landranger and Pathfinder maps the vertical interval is 10m (32.8ft). The old but famous 1 inch maps were on a smaller scale of 1:63360 (that is 1 inch to 1 mile) and the vertical interval was 50 feet, so the maps were much less detailed.
The contours representing the steeper side of the cone are ©
CO drawn close together, whereas those representing gender slopes are further apart. So, avoid those places on the map where the contours ‘sing together’ unless you intend to go rock climbing. Where cliffs are vertical or overhanging, contours and cliffs cannot be accurately represented; the contours just merge together into a single line. Sometimes rocky cones, like Ailsa Craig in the Firth of Clyde in Scotland, or Pike of Stickle, above Langdale, in the Lake District are too steep to be shown with contours and are shown with cliff markings, or even hachures on other maps, with the summit spot height numbered.
This island is similar in shape to our lump of plasticine, except that there are two summits, the westerly peak (C) being over 300m (1000ft) high, and the easterly top (E) being over 350m (1150ft). Notice that diere is a very steep slope at G with the contours very close together. However, the slope as shown by the contours is not as steep as I have shown it in the silhouette. In this and later diagrams I have exaggerated the vertical scales to show the shapes more clearly. Other features of the island are a flattish coastal plain at A, a steep upper slope at B, a flat pass or col at D and a uniform slope at F, where the gradient remains similar for some distance and the contours are reasonably evenly spaced.
A slope is concave when it is steeper at the top and flatter at the bottom. It is easier walking when you start in the valley but remember it gets harder the further you go. Another important consideration of slopes is that on concave slopes you have inter-visibility; a person at X can see another at Y, and the whole slope between is open to view. If you are looking for somebody or some wildlife such as red deer, or even searching for someone during a rescue, the task is easier with binoculars on a concave slope during the day in clear weather.
Convex or bulging slopes are shown as a mirror image of a concave slope on a contour map, except that the numbering of the contour lines is in reverse order; in other words, the steeper, closer together, contours are at the bottom of the slope. Red deer running away from walkers would get out of sight quicker in the dead ground. The bulge of the slope would also impede VHF radio waves during a search, so that rescue teams would have to install link radio men on facing hills to keep communications open.
The shapes of contours for spurs and valleys can be very similar, but contour numberings will distinguish between them. In countries like Britain with usually adequate rainfall there will be streams or rivers in the valleys; and since it is most unusual for a watercourse to follow the exact crest of a ridge or spur, the valleys or re-entrants will be obvious. This does not always apply in limestone country such as the Derbyshire White Peak District. Here, the valleys may have been river eroded as elsewhere, but except in spate conditions the streams have found their way underground through potholes, and so only dry valleys are left.
Without the marking of a stream or numbering of the contour lines it is impossible to tell, but if you do find such a puzzling square on a map follow the contours along until you find a set of numbers, and then you will be able to solve the problem.
Do these contour lines represent a very ordinary hill shape, or a hole in the ground? Although craters are not common in Britain, in Iceland they are two a penny, and they can be several kilometres in diameter. Without clues such as contour numbers or stream markings – whole rivers disappear into great holes in the Yorkshire Dales – you may be able to decide from the place names. ‘Mam Tor’ or ‘Lose Hill’ would indicate positive shapes, and ‘Buttertubs’ or ‘Pulpit Holes’ the reverse. Failing all else, if you find such a map marking, you will just have to visit the place to find out.
Pacing and timing
It is possible to buy a hand-held satellite navigator, although such a piece of equipment is expensive. Not only will this give your precise position, but also your altitude and the direction of travel to your next objective. These ground position systems are an exciting concept, but I suggest that you learn from first principles as the new technology cannot yet be infallible.
For any serious navigation a good stop watch is an asset and waterproof, digital watches are reasonably priced. Another way of measuring distance travelled in poor visibility is to count double paces.
At the start of navigation training days, say on winter moun-taincraft courses, I get everybody to count out their own personal number of double paces to cover 100m (330ft). Why double paces? At first it seems more difficult to count ‘One, step, two, step, three, step’, but when you get up to, ‘Seventy one, seventy two’ you will find it is much easier to count in doubles. At Outward Bound Loch Eil in Scotland we have a measured 100m (330ft) marked out between Summers Wing and the Workshop; my own count is invariably 63 double paces in a time of 1 minute 8 seconds, and I have found it to be surprisingly accurate over the years. When finding your own count you must walk normally, not striding out or mincing steps.
The method is accurate for fairly level ground where the going is not too rough. Featureless plateaux under a cover of hard snow come into this category, and this is where the method is most necessary. So for a navigation leg of 1km (½ mile) I would take just under 12 minutes, and my pacing would be 10 times 63 double paces. Remembering the number of 100 metres paced is the hardest bit; some people would pick up 10 pebbles and throw one away every 100m, but pebbles are hard to find on top of Lugnaquilla, in the Irish Wicklow Mountains, when it is plastered with snow.
Outdoor shops sell simple plastic ‘clickers’ that are attached to compass base plates; the idea is to click one counter every time you reach your personal number, then read off the number of 100 metres covered. A much better method is to shout out ‘One hundred’ every time. Another member of the group shouts ‘One hundred, two hundred, seven hundred’, or whatever. This keeps more people occupied, everyone knows what is going on, and mistakes are readily spotted. Accuracy will be very important in some circumstances.
The pacing method can also be used with reasonable accuracy to measure distance covered on slopes more gentle than about 1 in 10. At Loch Eil we have a measured distance staked out on rough ground at about that gradient. My normal speed double pacing up that is about 85 per 100m with a timing of 1 minute 20 seconds. Downhill pacing and timing are usually similar. Pacing up or down steeper slopes is inaccurate, and the method should not be relied on.
I have shown it to try and get you used to what is meant by a 100 per cent, or 1 in 1, slope or gradient. For every unit of distance horizontally there is the same distance of vertical climb. The method is somewhat confusing, but it is unfortunately getting more common.
To find out the gradient from the map, count the number of contours, then measure the horizontal distance. Similarly a gradient of 20 per cent means that the slope rises 20 units up for every 100 units along, say 200 metres for every kilometre (656ft for 0.625 miles). For a non-metric example (which is much harder to work out) look at Great Gable (2949ft) in the English Lake District from Burnthwaite Farm (350ft) in Wasdale Head. The vertical rise is 2600ft. The horizontal distance measured on the scale in the map margin (transfer it by marking the edge of a sheet of paper or use dividers) is 2350 yards = 7050ft. Divide 7050 by 2600 and the gradient is 1 in 2.71. To find the percentage gradient divide 100 by the ratio gradient. So 100 divided by 2.71 equals 36.9 per cent.
Gradients are often expressed in degrees; a 1 in 1 slope or 100 per cent is 45 degrees. A 1 in 2 slope is 50 per cent (about 27 degrees). It is a common error to overestimate the steepness of a slope, especially when seen face on.
The average slope of Great Gable from Burnthwaite Farm is just over 20 degrees, but it looks much steeper. The fact that you can see practically the whole slope means that it is a concave slope; and true enough, when you study the contour lines you find they are closer together near the top.
Walking down Grainsgill Beck recently in the Lake District, one of my companions found three tiny shapes on the map, one red, one blue and one black, about 150 metres apart. There was no interpretation in the margin legend so, curious, we made a detour to investigate. At one point there was nothing, at another mark there was a square of wooden fencing, and at the third there was a rain gauge in another square of fence. In this instance, I concluded that the legend was not comprehensive, but generally you will be able to find out what the conventional signs on a map mean by studying the legend. Maps vary quite widely, so I do not suggest that you learn all the signs for all the maps.
Apart from the depiction of footpaths and public rights of way, the signs most useful for walkers in hilly areas are contour lines and stream markings. Stream markings are particularly important in Scotland where footpaths may be unbridged and spate streams can be uncrossable.
Every spot in Britain has a unique reference on the National Grid. The grid is divided into squares with sides of 100km (62.S miles), each of which is identified by two letters. First identify the reference by quoting these two letters or by the map sheet number. On the back of the cover of
Landranger maps there is a map of the UK showing the areas covered by all 204 maps – Salisbury, for example, is covered by sheet 184. Printed in the margin is a diagram showing the sheets adjoining that particular map. Outdoor Leisure and Pathfinder maps have similar index maps.
You should always carry a compass in wild country and be able to use it, but you should need to use it only at night or in cloud. It is the sign of a good navigator that it is otherwise rarely used, because the map-reading should be sufficient. Little wonder that guided parties begin to show signs of nervousness when the leader brings out a compass. Having said that, there is no harm in checking until you know you are competent. I recommend that you use a baseplate compass. This type obviates the need for using a separate protractor.
Finding the grid bearing
The first thing to do before you take a compass bearing from the map is to guess what the bearing is going to be. This will help you to avoid major errors in calculating bearing. There are four quadrants in a circle and your guess need not even be particularly accurate, just as long as you get the direction in the correct quadrant.
All reputable maps have north at the top. This applies to New Zealand, South Africa and other countries in the southern hemisphere. In Britain, except for orienteering maps, the north at the top of the map is Grid North. Convention agrees that from any place if you go towards the top of the map parallel to the grid lines you are travelling zero degrees grid. Note that degrees are counted clockwise around the circle from zero.
Finding the magnetic bearing
The true poles lie on the earth’s axis of rotation. In most parts of the world the north-seeking part of the compass needle (often coloured red) does not point exactly to true north (for true north read grid north in Britain). There are exceptions: on what are known as agonic lines (for example, through the eastern Mediterranean), the compass needle points direcdy north and south, but these lines are not constant.
The red end of the needle points to the magnetic north pole, which wanders about a bit but is somewhere in the far north of Canada. The difference in angle is known as variation from grid north in Britain, and declination from true north in America. I shall call it variation. Anywhere in the world it is necessary to check the map margin variation diagram and tables to find if variation is west or east and the amount of the variation angle.
It is best to work out the magnetic bearing from first principles. If you learn rhymes they may get set in your mind and will be wrong if you then want to go walking in Alaska. However, in Britain, with west variation the magnetic bearing is almost always greater than the grid bearing numerically. The exception would be when you are walking nearly north. To a grid bearing of, say, 358 degrees, add 5 degrees variation, making 363 degrees magnetic. There is no such bearing of course, so the magnetic bearing would be 3 degrees.
Walking on a bearing
When you have decided on your grid bearing, add the variation (in Britain) and set the bearing on the capsule to the index mark. The markings are every 2 degrees. The capsule rotation on the baseplate should be fairly stiff so that it will not change accidentally. Standing up, hold the compass in front of you with the direction of travel arrow pointing dead ahead. Then turn your body round until the orienting arrow comes into line with the red end of the magnetic needle. The direction of travel arrow is now pointing to the magnetic bearing.
You should not be using the compass in good visibility, except for practice, or in dense brush or woodland. In poor visibility look as far ahead as you can, and identify an object (a rock or a clump of heather) in line with the direction of travel arrow and walk directly towards it. As you approach, another mark may appear dead in line with the first, and so you can continue. It is difficult to hold a line but some people can cope very well at the first attempt. Check the bearing from time to time, which may mean stopping, and also occasionally check that the capsule has not rotated to an incorrect bearing. If the whole party walk strictly in single file, a colleague at the rear can make regular stops to check the alignment of the group using another compass, shouting corrections ahead.
The magnetism of the earth as a whole is what makes the compass work, but local magnetic rocks, such as occur in Cyprus or the volcanic hills of the Scottish Hebrides, can cause compass anomalies. In these places there are no large, featureless plateaux that require long legs on a compass bearing, and there are plenty of very obvious rock features as landmarks. Otherwise you have to take bearings often, and average out the indications so that you are not too far out.
Other magnetic influences will throw your bearing way out; so make sure you do not rest the compass on the post of a steel wire fence. The hand you use to hold your compass should not be the one with your wrist watch, although gold rings will not affect it. Keep the compass away from your camera, stereo or the head of your ice-axe.
Bearings on distant objects
If your own position is beyond doubt and you want to identify a distant mountain, lake, church spire or something similar you can probably do so simply by orienting the map and lining up with natural features or with man-made landmarks such as dams, roads or plantation fences. Identify your position on the map and line up the places or objects you recognize. Then, by its position or direction in relation to the others, you can spot the feature you want.
If the identity of the feature is still not clear (let us say it is a particular mountain among several similar mountains) find out its magnetic bearing by sighting it along the baseplate of your compass, ensuring the direction of travel arrow points to the mountain. Hold the compass steady while you rotate the capsule until the red needle lines up with the orienteering arrow, and read off the bearing at the index mark.
Convert the magnetic bearing of the compass to a grid bearing. In Britain, or anywhere with a west variation, subtract the variation from the magnetic bearing to find the grid bearing. Transfer the grid bearing to the map, keeping the north/south lines parallel with the vertical grid lines. Move the baseplate on the map so that your position is under a long edge of the baseplate. That edge, or an extension of it using any straight edge such as a piece of paper, now aligns with the peak you want to identify.
Using a known landmark
You may be walking along a long ridge with lots of bumps in it, and you do not know quite how far along it you are, or you may be on a long fairly featureless path or lake shore, and again you do not know how far you have to go to get to your destination. Let us say it is a path along a lake shore. On the other side of the lake you can identify a hill with a definite feature, say a triangulation pillar, which is clearly shown on the map. When you have walked until you are more or less opposite the trig, point you will know your rough position.
To find your exact position, take a magnetic bearing, convert it to a grid bearing, and transfer it to the map as described above. You know one line of location, meaning you know you are on the path. Where an imaginary line along the compass baseplate intersects the path is your exact position.
To fix your position among a maze of broken, boggy ground, tiny lakes and streams, say in the middle of Rannoch Moor in Scotland, when you can see all the hills round about, you could use a method known as resection, although in this case it would be of more academic than practical value, but really good practice. Take a compass bearing on the triangulation pillar of Beinn a’Chrulaiste. Let us say it is 299 degrees. Subtract the variation (about 5 degrees west) from this magnetic bearing to give a grid bearing of 294 degrees. Plot this on the map from the summit through the middle of the moor, perhaps drawing a pencil line. Take another magnetic bearing on the trig, point of Stob na Cruaiche (32 degrees minus 5 degrees variation equals 27 degrees grid). Plot this line on the map also. Where the two lines intersect is your location. The intersection is at reference NN 340525 about 1km (½ mile) north of the foot of Loch Ba and 3.7km (2.31 miles) from the A82. To further confirm the position take, convert and plot a further bearing, this time on Meall a’Bhuiridh, the peak with the chairlifts and ski tows (262-5 = 257 degrees grid). It is unlikely that you will have been absolutely accurate in taking the bearings or in drawing the three lines, so the intersection will be in the form of a triangle or ‘cocked hat’, so the most accurate plot will be at the intersection of the medians. If there are several people in the group it is a good idea for everybody to take the bearings and plot the average values for even greater accuracy. !