| Map Reading |
| 3. The Shape of the Ground Definition of relief Relief is a general term applied to the shape of the ground on a vertical plane. The representation of relief on a map is the showing of the heights and shapes of the ground above the sea level. Elements in representation of relief There are two distinct elements in the representation of relief. These are: 1) Representation of heights 2) Representation of shape Units of vertical measure The standard unit of vertical measure for land maps is the meter Contours A contours is a line on the map joining points of equal height and the standard method of showing relief on topographical maps. Contouring combines an accurate indication of height with a good indication o shapes, especially when used in conjunction with spot heights. Contours are shown at a regular vertical interval (i.e. different in height between successive contours), which varies according to the scale of the amp and to the types of country mapped. The contour interval is always states in the lower margin of the map bear the graphical scales. On a 1/50,000 map, with average relief, the contour interval may be 10 or 20 meters (or 50 feets; at 1/250,000 scales it is probably 50 meters (or 200 feets). Contours are normally drawn as continuous lines( usually brown or similar colour).Every fourth or fifth contour (depending on the vertical interval) is call an Index Contour, and is shown by a thicker line. Contour values are placed in breaks made in contour lines; they are paced so that they read right way up when looking up the slope. Interpretation of contours Fig 3.1 shows a perspective view, side view and plan of a hill with its contours. The shape of a contour indicates the shape of the ground. When these contours are further apart, there is a greater distance to gain the height of the vertical interval between contours, and therefore the slopes is gentler than when the contours are closer together. When the contours are an equal distance apart, the slope is uniform. |
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| Fig 3.1 Contours |
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