The Ordnance Survey was a branch of the military set up to map Great Britain for the movement of supplies and coastal defence.

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1 How to Navigate Maps Introduction Maps from the Greek word Mappa meaning cloth or sheet represent a 3D feature on a 2D surface. They have developed considerably since the first known map which was a stone tablet of Babylon circa 600BC. The first step was Ptolmey s work Geographica in 2AD, which mapped the known world and included lines of latitude (horizontal lines) and longitude (vertical lines). These lines split the surface of the world into a grid. Most of the maps from 500AD to 1600AD took a Christian slant by centering them on Jerusalem. Was this the first Greenwich meridian? France was the first country to establish a national surveying programme in the 17 th century, but at least the British lead the Great Trigonometrical Survey of India in the 19 th century and discovered Mount Everest! The Ordnance Survey was a branch of the military set up to map Great Britain for the movement of supplies and coastal defence. A few wars and many years later and the military pushed mapping forward with Geographical Information Systems (computer databases with survey information) and satellite imaging. Scale Maps are available in different scales, typically 1:50,000 and 1:25,000. This means that 1 unit on the map represents 50,000 or 25,000 unit on ground in the real world. 1:50,000 Scale 1:25,000 Scale 1cm = 50,000cm 1cm = 500m 2cm = 1km 1cm = 25000cm 1cm = 250m 4cm = 1km There is a trade in benefits with these two popular scales. 1:50,000 can fit more area on a map but detail is lost. 1:25,000 concentrates on a smaller area but has more detail. Looking at the 1:25000 (fig.1) the contours show much more detail in their shape but because they are wider apart they seem paler and you would be forgiven for not recognising the severity of the south west slope from Ben Macdui. Ltd 2013 How to Navigate 1

2 Moving to the 1:50000 map (fig.2), it represents the general shape of the land much better than the 1: The contour lines appear much more defined and solid allowing you to very quickly gauge the shape of the mountain and the steepest slopes. Fig.1 Fig. 2 1:25000 map 1:50000 map The 1 :25000 does give much more detail on-the-ground such as the streams, lochans, field boundaries and boulders allowing for greater accuracy in micro-navigating. There are also other scales such as 1:40,000 and 1:10,000. The last are used for orienteering because they are so detailed but only show a very small area. For the map to be accurate the shape of the features must remain proportional and the angle must remain the same. 25 For example: The larger triangle is scaled down by 3 so it is 3 times shorter, three times narrower and the hypotenuse is also 3 times shorter. The angles have stayed the same which is why even though one is smaller, they both look alike Ltd 2013 How to Navigate 2

3 What information is on a map? A map must have a scale, a key and a north arrow. Maps also contain lots of other information, typically: 1. Grid lines 2. Surface features 3. Symbols 4. Contours Grid Lines NORTH 60 o N 30 o N 0 o 30 o S 60 o S SOUTH LINES OF LATITUDE (ALSO CALLED PARALLELS) Andy Stamp WEST NORTH When the image is taken from the globe and put on a flat sheet the grid lines are used as reference points. Vertical lines are called lines of Longitude and horizontal lines are called lines of Latitude. The National Grid was devised, based along latitude and longitude to separate the country into easily map-able sections. Each square is 100km 2 and is given a 2-letter code. Each square is then subdivided into 1km 2 grids, which is what you see on maps. The Grid is set at 49 North and 2 West. That means at these lines the National Grid (Grid North) matches the earth s lines of latitude and longitude (True North) perfectly. As one moves away from these points the error increases. Coordinates. As each 100km2 has its own code we can identify an area within it by using the numbers along the bottom of a map (Eastings) and along the side (Northings). This gives a four-figure reference and identifies a particular 1km square. We can break that square down into 10 along each side to give a six-figure grid reference which identifies an area 100m 2. EAST 30 o W 30 o E LINES OF 15 o W 0 o 15 o E SOUTH LONGITUDE (ALSO CALLED MERIDIANS) Ltd 2013 How to Navigate 3

4 When taking coordinates the area has two numbers. Always choose the lower of the numbers, in the bottom left. Surface The surface area on maps are represented by shading Symbols Read this direction first Symbols are used to demonstrate features. In the margin of the map there is a great deal of information. See how much there is for yourself. Then read this direction Ltd 2013 How to Navigate 4

5 Contours. Credit: Langmuir There are 4 basic principles to reading contours: 1 contours close together represent steep land. 2 contours wide apart represent flatter land. Contours are used to show the shape of the land. They were first used in 1730 to display the shape of the sea bed for maritime charts but were developed by a physicist who wanted to determine the mass of the earth by looking for deflection in precision pendulums when placed around a large land mass. The physicist chose Schiehallion in Scotland and developed contour line to make sure the pendulums were placed in particular locations. They are typically brown and rise in 10m increments (although this is sometimes 5m check the map key). Every 5 th contour the index contour is thicker to aid counting although on very steep sections only index contours are shown. 3 contours getting closer together towards the summit show a concave slope. 4 contours getting wider towards the summit show a convex slope. Ltd 2013 How to Navigate 5

6 A C E F B D SECTIONAL VIEW THROUGH X-X SECTION A-B CONCAVE SLOPE SECTION C-D CONVEX SLOPE SECTION E-F UNIFORM SLOPE Andy Stamp On the concave slope A-B the contour lines are closer together near the top. From the top you can see all the way to the bottom. On the convex slope C-D the contour lines are closer together near the bottom. You cannot see someone standing at the bottom when you're at the top. On the uniform slope E-F the contour lines have a constant separation. You can see the top from the bottom and vice versa. Ltd 2013 How to Navigate 6

7 J 230 G RUGGED COUNTRY H SPUR WITH KNOLL K RIDGE WITH A COL Andy Stamp Which way is up? 2 signs tell is if which way the slope runs: The numbers on the contour lines and also all rivers will join downhill a confluence not separate downhill! ROLLING COUNTRY Ltd 2013 How to Navigate 7

8 The Compass The compass is a devise that quite simply shows us where north is and allows us to find an angle from north it is that simple do not be afraid. It is quite possible to navigate in good visibility without a compass and this should be done as much as possible because the key to navigating is relating what is on the map to what s on the ground. Magnetic Variation There are 3 Norths! Grid North The direction of the vertical lines on maps. Magnetic North What the compass points to. True North The geographical North Pole, the axis on which the earth spins and where the earth s lines of longitude meet. You can ignore this one. Magnetic Grid True 0 100mm ruler Parallel line for taking bearings Read bearing from here North Arrow Features to look for in a good compass: 1:25000 Romer Direction Arrow 1:50000 Romer Magnifying glass Base plate Calibrations Compass housing Needle Large base plate Easy to handle when wearing gloves 1:25000 & 1:5000 Romers Quick measuring of distances and grid references Luminous markers For night navigation 0-100mm ruler For accurate distance measuring Magnifying glass To study fine detail At least 2 increments To measure bearings accurately All maps are set from a line of longitude, where Grid North lines up with True North. As one travels east or west from that line of longitude, magnetic north no longer lies perfectly With True North. Since the needle is a magnet it points to Magnetic North. The Magnetic Variation is the difference between these two north s depending are where you are in the world. The compass tallies Grid North to Magnetic North (and visa versa). Ltd 2013 How to Navigate 8

9 So what do we do with Magnetic Variation? When you work from the map to find a place on the ground the most common technique for navigating add the magnetic variation to your bearing. When you have located a feature on the ground and want to place it on the map, take the magnetic variation away from your bearing. Relating the map to the ground and back again! Here are two ways of remembering Setting the map means making the feature on the ground fit with the features on the map (or the other way around). In good visibility with plenty of definite features is fairly straightforward: The easy way Magnetic North Where the compass points Magnetic Variation The difference between magnetic and Grid Grid North Lines that point to the top of the map Grid to Mag Add Mag to Grid Get Rid! The map is very small and the world is very big so you add to your bearing to make up for it when working map-to-ground and take away when working ground-to-map. Line up what you see with what is on the map: This orientates the map so that if you were to walk in the direction planned on the map, you will move along the ground in the same direction. (image: Langmuir) True North Ignore Line of Datum Point Where the map is set At this point Grid North Lies on True North Ltd 2013 How to Navigate 9

10 The accurate way The really accurate way Credit: Langmuir Place the compass anywhere on the map and rotate the map until the red arrow on the compass lines up with the lines of longitude. This points the map north. Make sure your map is not upside down or you will be pointing it south! Place the compass on the map with the edge along a line of longitude and the bezel set to North. Add the Magnetic Variation and rotate both the map and the compass until the red needle lines up with the North Arrow Be sure to keep the map and compass level so the needle can rotate freely. Ltd 2013 How to Navigate 10

11 Taking a bearing map to ground In bad weather or at night it is not possible to navigate accurately without a compass. We use a compass to take a bearing (a direction of travel) from the map and place it on the ground: Credit: Langmuir 1) Identify where you are on the map (A) and where you want to go (B). Make sure the map is the right way up! 2) Use the edge of the compass or a parallel line on the base plate to join where you are to where you are going point the Direction Arrow from A to B. 3) Guess the rough angle about 45 in this example. To ensure that you don t make a 180 error. 4) Holding the compass firmly in place so as not to move it on the map, turn the compass housing so that the North Arrow lines up with the lines of Longitude and points north. 5) Add the Magnetic Variation 6) Place the compass flat in the palm of your hand in front of you. 7) Turn your whole body (not just the compass) until the needle is aligned with the North Arrow Put Red Fred in the Shed 8) Make sure the Direction Arrow is pointed away from you. 9) Using the Direction Arrow to sight a feature a short distance in front of you a boulder, mound, clump of grass etc. 10) Walk to it and then repeat the process Looking for a feature too far away may be difficult to walk to in bad weather or may disappear from sight as you walk up or downhill. Ltd 2013 How to Navigate 11

12 Taking a bearing ground to map Credit: Langmuir 1) Point the direction arrow at a feature you can clearly see. 2) Twist the compass housing until the North Arrow is underneath the magnetic needle. 3) Remove the magnetic variation 4) Place the compass on the map making sure the North arrow is parallel to the line of longitude and the North Arrow is pointing North. 5) Slide the compass into position so that the edge of the compass or a parallel line on the base plate intersect either your position or the feature whichever is known. Ignore the magnetic needle now, it is always pointing north! 6) Make sure the Direction Arrow is pointing away from your position or towards the feature. Ltd 2013 How to Navigate 12

13 Room for error There are several ways to make big errors the most common is walking of in the opposite direction. This is usual caused by Placing the compass on the map, with the Direction Arrow pointing towards your location, not away from it. Lining up the North Arrow along the lines of longitude but pointing south. Holding the map upside down but lining up the North Arrow to the top of the map pointing south. A question of Accuracy There are several steps involved in talking a bearing and walking along it. Error is cumulative at each step so if every step is done as accurately as possible the overall accuracy will be greater. This is what happens if we are not accurate at each stage: Problem Not locating your position accurately Not locating your target on the map accurately Not placing the compass on the map with precision Not holding the compass steady while you turn the compass housing Not lining up the North Arrow with the lines of Longitude accurately Not adding Magnetic Variation Not holding the compass level this allows the needle to float freely Not sighting a feature to walk to accurately Not re-sighting regularly or trying to walk too far between features. Result +/- 1 +/- 1 +/- 1 +/- 1 +/- 1 +/- 5 +/- 1 +/- 1 +/- 1 +/ error over 100m is an error of 23m left or right that s an error of 115m over 500m! Ltd 2013 How to Navigate 13

14 Distances Navigating takes two forms. In good visibility we are able to relate the features on the map to those on the ground and walk along safe in the knowledge that we can see where we are going. In bad visibility we need to use a compass. In this case we are often not walking from feature to feature but from point to point. The compass will accurately tell us the direction to walk in but not how far. Often we will be navigating to a landmark such as a stream, a hilltop or a wall, so we will know to stop when we start gong downhill again, get our feet wet or break our nose. Sometimes, however, these features are not that easy to find so we must walk a known distance. Over a short distance (up to 500m say), we pace. Beyond that we time our walking. Pacing Individual peoples stride varies but one persons stride is quite regular on flat ground, so counting how many double paces (every time your left or right feet touch the ground) over a 100m (or better still 1km for accuracy) can give us a pace to work with. Most peoples are between 55 and 65. The distance is measured on the map using either the roamer or the ruler. 1mm on a 1:25:000 map is 25m and 1mm on a 1:50000 map is 50m. The roamer is preferred especially when swapping between maps as no mental arithmetic is needed. A Pacing Card should be kept close to hand with basic calculations already worked out. Tip: My pace is 63. Over 500m I would have to count 315. It is much easier to have 5 beads on my compass and pull one down whenever I get to 63. I can then stop every 100m to check the map, adjust my rucksack etc. and start again knowing exactly where I am and where to start from. Timing A Timing Card can allow you to work out at which time you should arrive at your target. At the start of each leg start your stopwatch and stop it when you arrive. This will give you a base to work with. Subsequent legs can then be worked out. Remember to stop your stopwatch every time you stop on each leg and start it again when you restart! Other factors Both your timing and pacing will be affected by the following influences as the day goes on. Experience will allow you to account for these in your calculations, as will resetting your base time and pace regularly. Tiredness bad weather steep ground conditions underfoot poor route choice poor navigating poor fitness nothing to sight on doubt/fear/panic Ltd 2013 How to Navigate 14

15 TIME/DISTANCE/HEIGHT TABLES HORIZONTAL SPEED (km per hour) DISTANCE ,000 mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs TIME VERTICAL HEIGHT (IN MINUTES/SECONDS) 10 MTRS MTRS MTRS MTRS MTRS HORIZONTAL SPEED (km per hour) DISTANCE ,000 mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs mtrs per hour for vertical height 1 minute per contour line (vertical interval) 50 mtrs = 5 minutes (count every dark brown contour line) COMPASS VERSION/ATTACHMENT CUT OUT, FOLD & LAMINATE VERTICAL HEIGHT TIME (IN MINUTES/SECONDS) 10 MTRS MTRS MTRS MTRS MTRS mtrs per hour for vertical height 1 minute per contour line (vertical interval) 50 mtrs = 5 min (count every dark brown contour line) Ltd 2013 How to Navigate 15

16 A Strategy for Navigating Your Location How? Where? When? Features A Strategy for When Your Lost Stop! Orientate map and concentrate Where was I last and what have I passed? Have I made a parallel error? (E.G. Gone off down the wrong spur) Head for a DEFINITE feature If I am here, Can I navigate to the next feature? Night Navigation Do I know where I am? How am I going to get to my target? What is the Distance? What is the bearing? What is my pace and time? Start stopwatch What is happening underfoot? Am I there? Keep the Party together Enforce a Buddy system Appoint a responsible person to bring up the rear. Be aware of you party s needs and discomforts Keep everyone informed. Head torches and or light sticks for all members. Positive about previous route followed? Features to locate yourself? Attack Points? Collecting Features Catching Feature? Easiest route? Direct /Aiming Off / Contouring / Handrails? Pacing? Use roamer Timing? Combination? Guess first! Use previous legs as a guide Up hill / down hill / flat / contouring? Ltd 2013 How to Navigate 16

17 Essential Techniques for Navigating 460 Final destination Attack Point X Aiming Off Instead of aiming for a definite point along a linear feature, aim-off, to the left for example. When you reach the liner feature you know that if you turn right (in this example) you will reach your definite Aspect On rolling hills with very few features you can find your rough position very quickly by finding out which direction the hill slopes downhill. Point the Direction Arrow downhill the aspect but keep the compass level so the needle can spin freely. Take this bearing. Place the compass on the map roughly where you think you are. Line up the North Arrow with the grid lines. Move the compass up, down, left or right (but do not rotate!!!) until the contour line cross the edge of the compass at 90. This will tell you where on the hill you are but not how high up you are. You will need other features to tell you that. Attack Points If aiming for a definite but small feature, rather than trying to reach it directly, break the route into legs and aim for larger, more definite features close to your target. You can then home in over a final, shorter distance. 470 Ltd How to Navigate 17

18 Back Bearings To pinpoint your location along a liner route a path or ridge take a bearing to a feature and locate yourself buy identifying where the bearing intersect your path. Remember to subtract the Magnetic Variation. Catching Features A particular feature, beyond where you want to be so that if you hit it you know you have gone too far. Remember the angle of slope is a feature and often knowing where the hill becomes steep/gentle will help you out. Collecting Features A long route can be made simple by collecting features as you go. Over the bridge hand-rail along the forest.hit the stream right at confluence between the crags..to the lake. This Map Memory allows you to stow your map and walk without having to constantly check and take bearings. Contouring Sometimes it is easier and quicker to walk around a hill than walk directly over it. Other times the opposite is true. Ask your self; Which gives the longer time? The distance walked around or the direct distance plus 1 min for every contour climbed? Ltd How to Navigate 18

19 Somewhere in here Dog Legs Sometimes you may have to avoid a feature and walk around. 1. To maintain your correct position turn 90 and count the paces needed to avoid the feature. 2. Turn back 90 and continue to walk until you have passed the feature. 3. Turn Back 90 again to get onto your original direction of travel and count back your first number of paces. 4. Turn 90 to continue in your original direction. Hand-railing Use a linear feature to follow that will keep you on a known location following a stream to a confluence, a forest boundary to a corner or field boundaries. Resection To locate yourself take a bearing on three definite features and mark them on your map. Your location will be where the lines intersect. In reality it is a time consuming operation and it is often difficult to find three decent features that are spread all around. If the three features are all within 180 of each other the result is fairly inaccurate. If you can see three definite features try setting the map the easy way. Ltd How to Navigate 19

20 Thumbing When walking, keep you map folded to a reasonable size and as you walk past your collecting features move your thumb along the route. Whenever you have to find your position you won t waste time relocating amid a mass of contours. And it will probably be raining. And windy. Transits Coming inline with a linear feature or two known points (peaks or cairns for example) can pinpoint your location along another linear feature. Ltd How to Navigate 20