NAVIGATION. 2. Marginal Information

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1 NAVIGATION 1. The Map Definition and Handling A map is a graphic representation, usually on a plane surface and at an established scale, of natural or artificial features on the surface of a part or a whole of earth or other planetary body. The features are positioned relative to a co-ordinate reference system. Handling Maps deteriorate easily from many causes such as dirt and grime, liquids, the use of pens and other sharp objects and the repeated opening and folding of the map. To protect your maps keep them covered when not in use in clear contact, a plastic bag or a map case or board. Use pencil rather than pen and avoid sharp objects damaging the map. Correctly and carefully fold and unfold the map and keep it folded when not in use. Maps should be folded like a book so that you don t have to open the whole map to find the part you are using. 2. Marginal Information Marginal information is the information printed around the margins that is needed to use the map. This includes; The type of map (located at the top left) - Names the country, the scale and the type of map. The map title (located top center) - Refers usually to an important town on the map. The reference box - details of the map that includes the series, sheet number and edition of the map. Marginal Information also includes production information such as who made the map and on whose authority. It also lists the method of production and indicates accuracy. The Universal Grid Reference details the method of identifying a unique position on the earth s surface. The North Point Diagram shows the direction of True North, Grid North and Magnetic North. Scale and Contour information provide a scale for measuring distance and information on the distance between Contour Lines. The Legend contains coloured symbols used on the map.

2 Temperature and Rainfall graphs provide details of monthly variations in temperature and rainfall in the area. The Watercourse Guide indicates whether watercourses are perennial, intermittent or dry. Index to Adjoining Maps shows the relationship between this map and the surrounding maps. 3. Scale The scale of a map refers to the relationship (ratio) between distance on a map and the corresponding distance on the ground. The most common scale seen on cadet maps is 1:25000, which results in one grid square being equivalent to 1km squared. 4. Contour lines, intervals and spot heights Contour Lines A line which joins points of equal elevation (height) at a given level, such as mean sea level Contour Intervals The vertical distance or difference of elevation between contour lines Spot Height The altitude of a point that is shown on a map, usually a point of significant height 5. Magnetic Variation and northpoints The North Point Diagram shows the direction of True North, Grid North and Magnetic North. Grid North is the direction of a grid line which is parallel to the central meridian on the National Grid. True North is the direction of a meridian of longitude which converges on the North Pole. Magnetic North is the direction indicated by a magnetic compass. Magnetic North moves slowly with a variable rate The difference between magnetic north and true north is what we call magnetic variation To convert from a grid bearing to a magnetic bearing SUBTRACT To convert from magnetic to grid ADD 6. Grid References and distances Grid is made up or vertical and horizontal equally spaced lines that allow specification of certain areas on a map EASTINGS The vertical grid lines that are numbered west to east and divide the map west to east NORTHINGS The horizontal grid lines that are that are numbered south to north and divide the map south to north When giving grid references, eastings are given before northings 4- figure grid references give accuracy up to one grid square only

3 6 figure grid references give accuracy up to 100m 8 figure grid references give accuracy up to 10m Distances can be measured using a roamer, selecting appropriate scale, and placing the roamer next to the planned route Objects such as string can be used to measured curved routes Nav Data Sheet: Example Navigation Data sheet. The top row shows what you should write in each column e.g. Remarks- landmarks around the point Backbearings and resections: Backbearings- A backbearing is the opposite direction to your bearing. To calculate a back bearing, if your original bearing is below 180 degrees, then you add 180 degrees (e.g if you have a bearing of 40 degrees, your back bearing is 220 degrees). If your original bearing is above 180 degrees, then you subtract 180 degrees. (e.g if you have a bearing of 315 degrees, your back bearing would be 135 degrees)

4 Resections- cadets will complete a resection if they are lost in the bush. To complete a resection, follow these steps: Example Resection:

5 Pacing, timings and distance by day and by night: Timings Non tactical by day Tactical by day Tactical by night Undulating country 5km/hr 2km/hr 1km/hr Close flat country 3km/hr 1km/hr 100 to 500metres/hr ( km/hr) extremely rough country 1.5km/hr Factors that affect timings include: vegetation travel at night cadet load and fitness extremes of climate Pacings- Pacings are the most reliable method of measuring distance travelled. To calculate pacings: 1. Measure out 100m on the ground 2. Walk along this ground three times while counting your paces. (e.g 105, 110, 115) 3. Take the average of the three of them (e.g. 110) This is your paces for 100m. Remember to add or remove paces when walking up or down slopes.

6 An easy way to record paces is to transfer a stick or pebble from one hand to another every 100m. Distance remains the same day and night, however, remember it will take longer to travel a certain distance at night rather than during the day. NOTES: 1. Paces do not lengthen appreciably on steep downgrades. 2. Obstruction and traversing increases number of paces. 3. Cautious approach shortens paces. 4. Experience and practice are the only sure means of achieving accuracy.

7 Roma s and their use: Roma s are 360 degree protractors that are used to find a bearing from one point to another on a map, both in MILS and DEGREES. At the bottom of most Roma s there will be distance rules for maps with different scales which cadets can use to measure distance between points. Eastings and Northings: Northings run East to West, or laterally. Eastings run North to South. The diagrams above should explain.