NAVIGATION

1. NAVIGATION VOLUME 1: BASIC MAP READING

2. WHAT IS A MAP? HISTORY: • From the earliest days, exploration has been needed. • Early travellers used natural features to find their way. • By noting the position of stars, the sun & moon, man devised a method of finding out where he was. • Surroundings were sketched – early maps were often drawn on animal hide, stone or reed paper.

3. FINDING YOUR POSITION ON EARTH Longitude lines – also called Meridians, are circular. These run North to South. The Prime Meridian runs through Greenwich, UK & is numbered 0. Latitude Lines – these are parallel to the Equator which runs around the Earth at 0 degrees. This splits the Earth into two parts, these being the Northern & Southern Hemisphere.

4. RECORDING A POSITION If you put the latitude & longitude lines together on the same globe you will get a Matrix. With this system you can give a point’s exact position by stating its latitude, followed by its longitude in degrees & minutes. MAPS Today, every area of ground is covered by either survey or by satellite to give up to date maps of the world. Ordnance Survey – The UK is fortunate because it is served by possibly the best cartographers anywhere. The Ordnance Survey (OS) is a Government department based in Southampton. They produced their first map in 1791 for the Army. The maps that are mostly used within the ATC are Metric 726 series – 1: 50,000.

5. WHAT YOU WANT FROM A MAP If you need to get from A to B it is important that you find the best route so that you can avoid rivers, motorways and other such obstacles. By the end of this lesson you should be able to read a map, that will include: Symbols Grid References Distances The M726 Series Map is classed as a Topographical map which means it shows the shape & surface detail of the land, including natural & man-made features. A typical map would show: Rivers Valleys Hills Streams Woods Mountains Marshes Man-made features would include: Roads Canals Railways Towns Villages Power lines

6. TYPES OF MAP • The M726 Series is not the only type of Map available, there are maps for several other user groups: • Administrative Maps (Council boundaries/population surveys) • Historical Maps (Details monuments & layout of old buildings) • Marine Maps (Estuaries, sandbanks or wrecks) • Road Maps (Motorist route planning) • Outline Maps (Brief description of a specific area)

7. MAP SELECTION The map you use will depend on the activity undertaken:

8. MAP LANGUAGEMap Layout & Features • KEY: • Units of elevation • Angular difference • Degrees & minutes of longitude • Map title • Sheet ID • Conventional signs • How to give a grid ref. • Height conversion • Adjoining sheet details • North Points • Compilation & revision • Deviation of contours • Scale & lines • Grid numbers – Eastings • Degrees & minutes of latitude • Grid numbers - Northings

9. MAIN ELEMENTS OF A MAP Elevation When using a map you firstly check the units of height or elevation. This will be displayed in either feet or metres. Latitude & Longitude Latitude is expressed in degrees & minutes and marked along the right & left (East & West) hand side of the map. Longitude lines are marked along the top & bottom (North & South) of the map. These lines are not drawn on the map itself – it would be too confusing. North References: True North – Geographical North pole of the Earth – the point where the Earth’s axis meet the surface. Grid North – taken from the National Grid System, this is a system of imaginary lines that divide your map into a series of squares. Magnetic North – the point where a magnetic needle will align itself if freely suspended. The Earth has it’s own magnetic field. The Earth’s north & south magnetic poles do not coincide with the geographical poles – they are in fact 1200 miles apart!

10. Scale & Scale The scales of a map give you distances in nautical miles, statute miles & kilometres. A nautical mile =6080 feet =1.85km A statute mile =1760 yards =1,6093km A kilometre =0.6214 mile or 5/8 of a mile These scales are likely to be used by yourself when route planning. Triangulation Points Surveyors build up a map from a large number of triangles. The angles that are calculated from field work give accurate measurement on the ground. The points from where this information is taken are called triangulation points (Trig Points). These are small concrete pillars with a 3 channelled plate on top. On the map they are indicated by a blue triangle with a dot in the middle.

11. Conventional Signs - Features

17. Always give the number along the bottom first. Some people remember this by 'along the corridor and up the stairs' . Find the square you want, find the Eastings (across) value for the left side of the square, and then find the Northings (up) value for the bottom of the square. Write down the numbers and you have a four figure grid reference. For example the letter A in the example below is 02 across and 51 up and therefore has the four figure grid reference is 0251.

18. 6 Figure Grid ReferencesStart by working out the basic four figure grid reference. Then imagine the square is divided up into tenths. You can do this by eye or more accurately using a ruler. Using the example below the is in the square 0150, although more accurately it is 5 tenths across and 8 tenths up within the grid square 0150 and therefore has the six figure grid reference 017508.

19. ANY QUESTIONS?